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c++ source #1
Output
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Intel asm syntax
Demangle identifiers
Verbose demangling
Filters
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Debug intrinsics
Compiler
6502-c++ 11.1.0
ARM GCC 10.2.0
ARM GCC 10.3.0
ARM GCC 10.4.0
ARM GCC 10.5.0
ARM GCC 11.1.0
ARM GCC 11.2.0
ARM GCC 11.3.0
ARM GCC 11.4.0
ARM GCC 12.1.0
ARM GCC 12.2.0
ARM GCC 12.3.0
ARM GCC 12.4.0
ARM GCC 13.1.0
ARM GCC 13.2.0
ARM GCC 13.2.0 (unknown-eabi)
ARM GCC 13.3.0
ARM GCC 13.3.0 (unknown-eabi)
ARM GCC 14.1.0
ARM GCC 14.1.0 (unknown-eabi)
ARM GCC 14.2.0
ARM GCC 14.2.0 (unknown-eabi)
ARM GCC 4.5.4
ARM GCC 4.6.4
ARM GCC 5.4
ARM GCC 6.3.0
ARM GCC 6.4.0
ARM GCC 7.3.0
ARM GCC 7.5.0
ARM GCC 8.2.0
ARM GCC 8.5.0
ARM GCC 9.3.0
ARM GCC 9.4.0
ARM GCC 9.5.0
ARM GCC trunk
ARM gcc 10.2.1 (none)
ARM gcc 10.3.1 (2021.07 none)
ARM gcc 10.3.1 (2021.10 none)
ARM gcc 11.2.1 (none)
ARM gcc 5.4.1 (none)
ARM gcc 7.2.1 (none)
ARM gcc 8.2 (WinCE)
ARM gcc 8.3.1 (none)
ARM gcc 9.2.1 (none)
ARM msvc v19.0 (WINE)
ARM msvc v19.10 (WINE)
ARM msvc v19.14 (WINE)
ARM64 Morello gcc 10.1 Alpha 2
ARM64 gcc 10.2
ARM64 gcc 10.3
ARM64 gcc 10.4
ARM64 gcc 10.5.0
ARM64 gcc 11.1
ARM64 gcc 11.2
ARM64 gcc 11.3
ARM64 gcc 11.4.0
ARM64 gcc 12.1
ARM64 gcc 12.2.0
ARM64 gcc 12.3.0
ARM64 gcc 12.4.0
ARM64 gcc 13.1.0
ARM64 gcc 13.2.0
ARM64 gcc 13.3.0
ARM64 gcc 14.1.0
ARM64 gcc 14.2.0
ARM64 gcc 4.9.4
ARM64 gcc 5.4
ARM64 gcc 5.5.0
ARM64 gcc 6.3
ARM64 gcc 6.4
ARM64 gcc 7.3
ARM64 gcc 7.5
ARM64 gcc 8.2
ARM64 gcc 8.5
ARM64 gcc 9.3
ARM64 gcc 9.4
ARM64 gcc 9.5
ARM64 gcc trunk
ARM64 msvc v19.14 (WINE)
AVR gcc 10.3.0
AVR gcc 11.1.0
AVR gcc 12.1.0
AVR gcc 12.2.0
AVR gcc 12.3.0
AVR gcc 12.4.0
AVR gcc 13.1.0
AVR gcc 13.2.0
AVR gcc 13.3.0
AVR gcc 14.1.0
AVR gcc 14.2.0
AVR gcc 4.5.4
AVR gcc 4.6.4
AVR gcc 5.4.0
AVR gcc 9.2.0
AVR gcc 9.3.0
Arduino Mega (1.8.9)
Arduino Uno (1.8.9)
BPF clang (trunk)
BPF clang 13.0.0
BPF clang 14.0.0
BPF clang 15.0.0
BPF clang 16.0.0
BPF clang 17.0.1
BPF clang 18.1.0
BPF clang 19.1.0
BPF gcc 13.1.0
BPF gcc 13.2.0
BPF gcc 13.3.0
BPF gcc trunk
EDG (experimental reflection)
EDG 6.5
EDG 6.5 (GNU mode gcc 13)
EDG 6.6
EDG 6.6 (GNU mode gcc 13)
FRC 2019
FRC 2020
FRC 2023
HPPA gcc 14.2.0
KVX ACB 4.1.0 (GCC 7.5.0)
KVX ACB 4.1.0-cd1 (GCC 7.5.0)
KVX ACB 4.10.0 (GCC 10.3.1)
KVX ACB 4.11.1 (GCC 10.3.1)
KVX ACB 4.12.0 (GCC 11.3.0)
KVX ACB 4.2.0 (GCC 7.5.0)
KVX ACB 4.3.0 (GCC 7.5.0)
KVX ACB 4.4.0 (GCC 7.5.0)
KVX ACB 4.6.0 (GCC 9.4.1)
KVX ACB 4.8.0 (GCC 9.4.1)
KVX ACB 4.9.0 (GCC 9.4.1)
KVX ACB 5.0.0 (GCC 12.2.1)
LoongArch64 clang (trunk)
LoongArch64 clang 17.0.1
LoongArch64 clang 18.1.0
LoongArch64 clang 19.1.0
M68K gcc 13.1.0
M68K gcc 13.2.0
M68K gcc 13.3.0
M68K gcc 14.1.0
M68K gcc 14.2.0
M68k clang (trunk)
MRISC32 gcc (trunk)
MSP430 gcc 4.5.3
MSP430 gcc 5.3.0
MSP430 gcc 6.2.1
MinGW clang 14.0.3
MinGW clang 14.0.6
MinGW clang 15.0.7
MinGW clang 16.0.0
MinGW clang 16.0.2
MinGW gcc 11.3.0
MinGW gcc 12.1.0
MinGW gcc 12.2.0
MinGW gcc 13.1.0
RISC-V (32-bits) gcc (trunk)
RISC-V (32-bits) gcc 10.2.0
RISC-V (32-bits) gcc 10.3.0
RISC-V (32-bits) gcc 11.2.0
RISC-V (32-bits) gcc 11.3.0
RISC-V (32-bits) gcc 11.4.0
RISC-V (32-bits) gcc 12.1.0
RISC-V (32-bits) gcc 12.2.0
RISC-V (32-bits) gcc 12.3.0
RISC-V (32-bits) gcc 12.4.0
RISC-V (32-bits) gcc 13.1.0
RISC-V (32-bits) gcc 13.2.0
RISC-V (32-bits) gcc 13.3.0
RISC-V (32-bits) gcc 14.1.0
RISC-V (32-bits) gcc 14.2.0
RISC-V (32-bits) gcc 8.2.0
RISC-V (32-bits) gcc 8.5.0
RISC-V (32-bits) gcc 9.4.0
RISC-V (64-bits) gcc (trunk)
RISC-V (64-bits) gcc 10.2.0
RISC-V (64-bits) gcc 10.3.0
RISC-V (64-bits) gcc 11.2.0
RISC-V (64-bits) gcc 11.3.0
RISC-V (64-bits) gcc 11.4.0
RISC-V (64-bits) gcc 12.1.0
RISC-V (64-bits) gcc 12.2.0
RISC-V (64-bits) gcc 12.3.0
RISC-V (64-bits) gcc 12.4.0
RISC-V (64-bits) gcc 13.1.0
RISC-V (64-bits) gcc 13.2.0
RISC-V (64-bits) gcc 13.3.0
RISC-V (64-bits) gcc 14.1.0
RISC-V (64-bits) gcc 14.2.0
RISC-V (64-bits) gcc 8.2.0
RISC-V (64-bits) gcc 8.5.0
RISC-V (64-bits) gcc 9.4.0
RISC-V rv32gc clang (trunk)
RISC-V rv32gc clang 10.0.0
RISC-V rv32gc clang 10.0.1
RISC-V rv32gc clang 11.0.0
RISC-V rv32gc clang 11.0.1
RISC-V rv32gc clang 12.0.0
RISC-V rv32gc clang 12.0.1
RISC-V rv32gc clang 13.0.0
RISC-V rv32gc clang 13.0.1
RISC-V rv32gc clang 14.0.0
RISC-V rv32gc clang 15.0.0
RISC-V rv32gc clang 16.0.0
RISC-V rv32gc clang 17.0.1
RISC-V rv32gc clang 18.1.0
RISC-V rv32gc clang 19.1.0
RISC-V rv32gc clang 9.0.0
RISC-V rv32gc clang 9.0.1
RISC-V rv64gc clang (trunk)
RISC-V rv64gc clang 10.0.0
RISC-V rv64gc clang 10.0.1
RISC-V rv64gc clang 11.0.0
RISC-V rv64gc clang 11.0.1
RISC-V rv64gc clang 12.0.0
RISC-V rv64gc clang 12.0.1
RISC-V rv64gc clang 13.0.0
RISC-V rv64gc clang 13.0.1
RISC-V rv64gc clang 14.0.0
RISC-V rv64gc clang 15.0.0
RISC-V rv64gc clang 16.0.0
RISC-V rv64gc clang 17.0.1
RISC-V rv64gc clang 18.1.0
RISC-V rv64gc clang 19.1.0
RISC-V rv64gc clang 9.0.0
RISC-V rv64gc clang 9.0.1
Raspbian Buster
Raspbian Stretch
SPARC LEON gcc 12.2.0
SPARC LEON gcc 12.3.0
SPARC LEON gcc 12.4.0
SPARC LEON gcc 13.1.0
SPARC LEON gcc 13.2.0
SPARC LEON gcc 13.3.0
SPARC LEON gcc 14.1.0
SPARC LEON gcc 14.2.0
SPARC gcc 12.2.0
SPARC gcc 12.3.0
SPARC gcc 12.4.0
SPARC gcc 13.1.0
SPARC gcc 13.2.0
SPARC gcc 13.3.0
SPARC gcc 14.1.0
SPARC gcc 14.2.0
SPARC64 gcc 12.2.0
SPARC64 gcc 12.3.0
SPARC64 gcc 12.4.0
SPARC64 gcc 13.1.0
SPARC64 gcc 13.2.0
SPARC64 gcc 13.3.0
SPARC64 gcc 14.1.0
SPARC64 gcc 14.2.0
TI C6x gcc 12.2.0
TI C6x gcc 12.3.0
TI C6x gcc 12.4.0
TI C6x gcc 13.1.0
TI C6x gcc 13.2.0
TI C6x gcc 13.3.0
TI C6x gcc 14.1.0
TI C6x gcc 14.2.0
TI CL430 21.6.1
VAX gcc NetBSDELF 10.4.0
VAX gcc NetBSDELF 10.5.0 (Nov 15 03:50:22 2023)
WebAssembly clang (trunk)
Xtensa ESP32 gcc 11.2.0 (2022r1)
Xtensa ESP32 gcc 12.2.0 (20230208)
Xtensa ESP32 gcc 8.2.0 (2019r2)
Xtensa ESP32 gcc 8.2.0 (2020r1)
Xtensa ESP32 gcc 8.2.0 (2020r2)
Xtensa ESP32 gcc 8.4.0 (2020r3)
Xtensa ESP32 gcc 8.4.0 (2021r1)
Xtensa ESP32 gcc 8.4.0 (2021r2)
Xtensa ESP32-S2 gcc 11.2.0 (2022r1)
Xtensa ESP32-S2 gcc 12.2.0 (20230208)
Xtensa ESP32-S2 gcc 8.2.0 (2019r2)
Xtensa ESP32-S2 gcc 8.2.0 (2020r1)
Xtensa ESP32-S2 gcc 8.2.0 (2020r2)
Xtensa ESP32-S2 gcc 8.4.0 (2020r3)
Xtensa ESP32-S2 gcc 8.4.0 (2021r1)
Xtensa ESP32-S2 gcc 8.4.0 (2021r2)
Xtensa ESP32-S3 gcc 11.2.0 (2022r1)
Xtensa ESP32-S3 gcc 12.2.0 (20230208)
Xtensa ESP32-S3 gcc 8.4.0 (2020r3)
Xtensa ESP32-S3 gcc 8.4.0 (2021r1)
Xtensa ESP32-S3 gcc 8.4.0 (2021r2)
arm64 msvc v19.20 VS16.0
arm64 msvc v19.21 VS16.1
arm64 msvc v19.22 VS16.2
arm64 msvc v19.23 VS16.3
arm64 msvc v19.24 VS16.4
arm64 msvc v19.25 VS16.5
arm64 msvc v19.27 VS16.7
arm64 msvc v19.28 VS16.8
arm64 msvc v19.28 VS16.9
arm64 msvc v19.29 VS16.10
arm64 msvc v19.29 VS16.11
arm64 msvc v19.30 VS17.0
arm64 msvc v19.31 VS17.1
arm64 msvc v19.32 VS17.2
arm64 msvc v19.33 VS17.3
arm64 msvc v19.34 VS17.4
arm64 msvc v19.35 VS17.5
arm64 msvc v19.36 VS17.6
arm64 msvc v19.37 VS17.7
arm64 msvc v19.38 VS17.8
arm64 msvc v19.39 VS17.9
arm64 msvc v19.40 VS17.10
arm64 msvc v19.latest
armv7-a clang (trunk)
armv7-a clang 10.0.0
armv7-a clang 10.0.1
armv7-a clang 11.0.0
armv7-a clang 11.0.1
armv7-a clang 12.0.0
armv7-a clang 12.0.1
armv7-a clang 13.0.0
armv7-a clang 13.0.1
armv7-a clang 14.0.0
armv7-a clang 15.0.0
armv7-a clang 16.0.0
armv7-a clang 17.0.1
armv7-a clang 18.1.0
armv7-a clang 19.1.0
armv7-a clang 9.0.0
armv7-a clang 9.0.1
armv8-a clang (all architectural features, trunk)
armv8-a clang (trunk)
armv8-a clang 10.0.0
armv8-a clang 10.0.1
armv8-a clang 11.0.0
armv8-a clang 11.0.1
armv8-a clang 12.0.0
armv8-a clang 13.0.0
armv8-a clang 14.0.0
armv8-a clang 15.0.0
armv8-a clang 16.0.0
armv8-a clang 17.0.1
armv8-a clang 18.1.0
armv8-a clang 19.1.0
armv8-a clang 9.0.0
armv8-a clang 9.0.1
clang-cl 18.1.0
ellcc 0.1.33
ellcc 0.1.34
ellcc 2017-07-16
hexagon-clang 16.0.5
llvm-mos atari2600-3e
llvm-mos atari2600-4k
llvm-mos atari2600-common
llvm-mos atari5200-supercart
llvm-mos atari8-cart-megacart
llvm-mos atari8-cart-std
llvm-mos atari8-cart-xegs
llvm-mos atari8-common
llvm-mos atari8-dos
llvm-mos c128
llvm-mos c64
llvm-mos commodore
llvm-mos cpm65
llvm-mos cx16
llvm-mos dodo
llvm-mos eater
llvm-mos mega65
llvm-mos nes
llvm-mos nes-action53
llvm-mos nes-cnrom
llvm-mos nes-gtrom
llvm-mos nes-mmc1
llvm-mos nes-mmc3
llvm-mos nes-nrom
llvm-mos nes-unrom
llvm-mos nes-unrom-512
llvm-mos osi-c1p
llvm-mos pce
llvm-mos pce-cd
llvm-mos pce-common
llvm-mos pet
llvm-mos rp6502
llvm-mos rpc8e
llvm-mos supervision
llvm-mos vic20
loongarch64 gcc 12.2.0
loongarch64 gcc 12.3.0
loongarch64 gcc 12.4.0
loongarch64 gcc 13.1.0
loongarch64 gcc 13.2.0
loongarch64 gcc 13.3.0
loongarch64 gcc 14.1.0
loongarch64 gcc 14.2.0
mips clang 13.0.0
mips clang 14.0.0
mips clang 15.0.0
mips clang 16.0.0
mips clang 17.0.1
mips clang 18.1.0
mips clang 19.1.0
mips gcc 11.2.0
mips gcc 12.1.0
mips gcc 12.2.0
mips gcc 12.3.0
mips gcc 12.4.0
mips gcc 13.1.0
mips gcc 13.2.0
mips gcc 13.3.0
mips gcc 14.1.0
mips gcc 14.2.0
mips gcc 4.9.4
mips gcc 5.4
mips gcc 5.5.0
mips gcc 9.3.0 (codescape)
mips gcc 9.5.0
mips64 (el) gcc 12.1.0
mips64 (el) gcc 12.2.0
mips64 (el) gcc 12.3.0
mips64 (el) gcc 12.4.0
mips64 (el) gcc 13.1.0
mips64 (el) gcc 13.2.0
mips64 (el) gcc 13.3.0
mips64 (el) gcc 14.1.0
mips64 (el) gcc 14.2.0
mips64 (el) gcc 4.9.4
mips64 (el) gcc 5.4.0
mips64 (el) gcc 5.5.0
mips64 (el) gcc 9.5.0
mips64 clang 13.0.0
mips64 clang 14.0.0
mips64 clang 15.0.0
mips64 clang 16.0.0
mips64 clang 17.0.1
mips64 clang 18.1.0
mips64 clang 19.1.0
mips64 gcc 11.2.0
mips64 gcc 12.1.0
mips64 gcc 12.2.0
mips64 gcc 12.3.0
mips64 gcc 12.4.0
mips64 gcc 13.1.0
mips64 gcc 13.2.0
mips64 gcc 13.3.0
mips64 gcc 14.1.0
mips64 gcc 14.2.0
mips64 gcc 4.9.4
mips64 gcc 5.4.0
mips64 gcc 5.5.0
mips64 gcc 9.5.0
mips64el clang 13.0.0
mips64el clang 14.0.0
mips64el clang 15.0.0
mips64el clang 16.0.0
mips64el clang 17.0.1
mips64el clang 18.1.0
mips64el clang 19.1.0
mipsel clang 13.0.0
mipsel clang 14.0.0
mipsel clang 15.0.0
mipsel clang 16.0.0
mipsel clang 17.0.1
mipsel clang 18.1.0
mipsel clang 19.1.0
mipsel gcc 12.1.0
mipsel gcc 12.2.0
mipsel gcc 12.3.0
mipsel gcc 12.4.0
mipsel gcc 13.1.0
mipsel gcc 13.2.0
mipsel gcc 13.3.0
mipsel gcc 14.1.0
mipsel gcc 14.2.0
mipsel gcc 4.9.4
mipsel gcc 5.4.0
mipsel gcc 5.5.0
mipsel gcc 9.5.0
nanoMIPS gcc 6.3.0 (mtk)
power gcc 11.2.0
power gcc 12.1.0
power gcc 12.2.0
power gcc 12.3.0
power gcc 12.4.0
power gcc 13.1.0
power gcc 13.2.0
power gcc 13.3.0
power gcc 14.1.0
power gcc 14.2.0
power gcc 4.8.5
power64 AT12.0 (gcc8)
power64 AT13.0 (gcc9)
power64 gcc 11.2.0
power64 gcc 12.1.0
power64 gcc 12.2.0
power64 gcc 12.3.0
power64 gcc 12.4.0
power64 gcc 13.1.0
power64 gcc 13.2.0
power64 gcc 13.3.0
power64 gcc 14.1.0
power64 gcc 14.2.0
power64 gcc trunk
power64le AT12.0 (gcc8)
power64le AT13.0 (gcc9)
power64le clang (trunk)
power64le gcc 11.2.0
power64le gcc 12.1.0
power64le gcc 12.2.0
power64le gcc 12.3.0
power64le gcc 12.4.0
power64le gcc 13.1.0
power64le gcc 13.2.0
power64le gcc 13.3.0
power64le gcc 14.1.0
power64le gcc 14.2.0
power64le gcc 6.3.0
power64le gcc trunk
powerpc64 clang (trunk)
s390x gcc 11.2.0
s390x gcc 12.1.0
s390x gcc 12.2.0
s390x gcc 12.3.0
s390x gcc 12.4.0
s390x gcc 13.1.0
s390x gcc 13.2.0
s390x gcc 13.3.0
s390x gcc 14.1.0
s390x gcc 14.2.0
sh gcc 12.2.0
sh gcc 12.3.0
sh gcc 12.4.0
sh gcc 13.1.0
sh gcc 13.2.0
sh gcc 13.3.0
sh gcc 14.1.0
sh gcc 14.2.0
sh gcc 4.9.4
sh gcc 9.5.0
vast (trunk)
x64 msvc v19.0 (WINE)
x64 msvc v19.10 (WINE)
x64 msvc v19.14 (WINE)
x64 msvc v19.20 VS16.0
x64 msvc v19.21 VS16.1
x64 msvc v19.22 VS16.2
x64 msvc v19.23 VS16.3
x64 msvc v19.24 VS16.4
x64 msvc v19.25 VS16.5
x64 msvc v19.27 VS16.7
x64 msvc v19.28 VS16.8
x64 msvc v19.28 VS16.9
x64 msvc v19.29 VS16.10
x64 msvc v19.29 VS16.11
x64 msvc v19.30 VS17.0
x64 msvc v19.31 VS17.1
x64 msvc v19.32 VS17.2
x64 msvc v19.33 VS17.3
x64 msvc v19.34 VS17.4
x64 msvc v19.35 VS17.5
x64 msvc v19.36 VS17.6
x64 msvc v19.37 VS17.7
x64 msvc v19.38 VS17.8
x64 msvc v19.39 VS17.9
x64 msvc v19.40 VS17.10
x64 msvc v19.latest
x86 djgpp 4.9.4
x86 djgpp 5.5.0
x86 djgpp 6.4.0
x86 djgpp 7.2.0
x86 msvc v19.0 (WINE)
x86 msvc v19.10 (WINE)
x86 msvc v19.14 (WINE)
x86 msvc v19.20 VS16.0
x86 msvc v19.21 VS16.1
x86 msvc v19.22 VS16.2
x86 msvc v19.23 VS16.3
x86 msvc v19.24 VS16.4
x86 msvc v19.25 VS16.5
x86 msvc v19.27 VS16.7
x86 msvc v19.28 VS16.8
x86 msvc v19.28 VS16.9
x86 msvc v19.29 VS16.10
x86 msvc v19.29 VS16.11
x86 msvc v19.30 VS17.0
x86 msvc v19.31 VS17.1
x86 msvc v19.32 VS17.2
x86 msvc v19.33 VS17.3
x86 msvc v19.34 VS17.4
x86 msvc v19.35 VS17.5
x86 msvc v19.36 VS17.6
x86 msvc v19.37 VS17.7
x86 msvc v19.38 VS17.8
x86 msvc v19.39 VS17.9
x86 msvc v19.40 VS17.10
x86 msvc v19.latest
x86 nvc++ 22.11
x86 nvc++ 22.7
x86 nvc++ 22.9
x86 nvc++ 23.1
x86 nvc++ 23.11
x86 nvc++ 23.3
x86 nvc++ 23.5
x86 nvc++ 23.7
x86 nvc++ 23.9
x86 nvc++ 24.1
x86 nvc++ 24.3
x86 nvc++ 24.5
x86 nvc++ 24.7
x86-64 Zapcc 190308
x86-64 clang (EricWF contracts)
x86-64 clang (amd-staging)
x86-64 clang (assertions trunk)
x86-64 clang (clangir)
x86-64 clang (dascandy contracts)
x86-64 clang (experimental -Wlifetime)
x86-64 clang (experimental P1061)
x86-64 clang (experimental P1144)
x86-64 clang (experimental P1221)
x86-64 clang (experimental P2996)
x86-64 clang (experimental P3068)
x86-64 clang (experimental P3309)
x86-64 clang (experimental P3367)
x86-64 clang (experimental P3372)
x86-64 clang (experimental metaprogramming - P2632)
x86-64 clang (old concepts branch)
x86-64 clang (p1974)
x86-64 clang (pattern matching - P2688)
x86-64 clang (reflection)
x86-64 clang (resugar)
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zig c++ 0.10.0
zig c++ 0.11.0
zig c++ 0.12.0
zig c++ 0.12.1
zig c++ 0.13.0
zig c++ 0.6.0
zig c++ 0.7.0
zig c++ 0.7.1
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zig c++ trunk
Options
Source code
/// // optional - An implementation of std::optional with extensions // Written in 2017 by Simon Brand (tartanllama@gmail.com, @TartanLlama) // // To the extent possible under law, the author(s) have dedicated all // copyright and related and neighboring rights to this software to the // public domain worldwide. This software is distributed without any warranty. // // You should have received a copy of the CC0 Public Domain Dedication // along with this software. If not, see // <http://creativecommons.org/publicdomain/zero/1.0/>. /// #ifndef TL_OPTIONAL_HPP #define TL_OPTIONAL_HPP #define TL_OPTIONAL_VERSION_MAJOR 0 #define TL_OPTIONAL_VERSION_MINOR 5 #include <functional> #include <new> #include <optional> #include <type_traits> #include <utility> #include <map> #include <iostream> #include <string> #if (defined(_MSC_VER) && _MSC_VER == 1900) #define TL_OPTIONAL_MSVC2015 #endif #if (defined(__GNUC__) && __GNUC__ == 4 && __GNUC_MINOR__ <= 9 && \ !defined(__clang__)) #define TL_OPTIONAL_GCC49 #endif #if (defined(__GNUC__) && __GNUC__ == 5 && __GNUC_MINOR__ <= 4 && \ !defined(__clang__)) #define TL_OPTIONAL_GCC54 #endif #if (defined(__GNUC__) && __GNUC__ == 5 && __GNUC_MINOR__ <= 5 && \ !defined(__clang__)) #define TL_OPTIONAL_GCC55 #endif #if (defined(__GNUC__) && __GNUC__ == 4 && __GNUC_MINOR__ <= 9 && \ !defined(__clang__)) // GCC < 5 doesn't support overloading on const&& for member functions #define TL_OPTIONAL_NO_CONSTRR // GCC < 5 doesn't support some standard C++11 type traits #define TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) \ std::has_trivial_copy_constructor<T>::value #define TL_OPTIONAL_IS_TRIVIALLY_COPY_ASSIGNABLE(T) \ std::has_trivial_copy_assign<T>::value // This one will be different for GCC 5.7 if it's ever supported #define TL_OPTIONAL_IS_TRIVIALLY_DESTRUCTIBLE(T) \ std::is_trivially_destructible<T>::value // GCC 5 < v < 8 has a bug in is_trivially_copy_constructible which breaks // std::vector for non-copyable types #elif (defined(__GNUC__) && __GNUC__ < 8 && !defined(__clang__)) #ifndef TL_GCC_LESS_8_TRIVIALLY_COPY_CONSTRUCTIBLE_MUTEX #define TL_GCC_LESS_8_TRIVIALLY_COPY_CONSTRUCTIBLE_MUTEX namespace tl { namespace detail { template <class T> struct is_trivially_copy_constructible : std::is_trivially_copy_constructible<T> {}; #ifdef _GLIBCXX_VECTOR template <class T, class A> struct is_trivially_copy_constructible<std::vector<T, A>> : std::is_trivially_copy_constructible<T> {}; #endif } // namespace detail } // namespace tl #endif #define TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) \ tl::detail::is_trivially_copy_constructible<T>::value #define TL_OPTIONAL_IS_TRIVIALLY_COPY_ASSIGNABLE(T) \ std::is_trivially_copy_assignable<T>::value #define TL_OPTIONAL_IS_TRIVIALLY_DESTRUCTIBLE(T) \ std::is_trivially_destructible<T>::value #else #define TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) \ std::is_trivially_copy_constructible<T>::value #define TL_OPTIONAL_IS_TRIVIALLY_COPY_ASSIGNABLE(T) \ std::is_trivially_copy_assignable<T>::value #define TL_OPTIONAL_IS_TRIVIALLY_DESTRUCTIBLE(T) \ std::is_trivially_destructible<T>::value #endif #if __cplusplus > 201103L #define TL_OPTIONAL_CXX14 #endif // constexpr implies const in C++11, not C++14 #if (__cplusplus == 201103L || defined(TL_OPTIONAL_MSVC2015) || \ defined(TL_OPTIONAL_GCC49)) #define TL_OPTIONAL_11_CONSTEXPR #else #define TL_OPTIONAL_11_CONSTEXPR constexpr #endif namespace tl { #ifndef TL_MONOSTATE_INPLACE_MUTEX #define TL_MONOSTATE_INPLACE_MUTEX /// Used to represent an optional with no data; essentially a bool class monostate {}; /// A tag type to tell optional to construct its value in-place struct in_place_t { explicit in_place_t() = default; }; /// A tag to tell optional to construct its value in-place static constexpr in_place_t in_place{}; #endif template <class T> class optional; namespace detail { #ifndef TL_TRAITS_MUTEX #define TL_TRAITS_MUTEX // C++14-style aliases for brevity template <class T> using remove_const_t = typename std::remove_const<T>::type; template <class T> using remove_reference_t = typename std::remove_reference<T>::type; template <class T> using decay_t = typename std::decay<T>::type; template <bool E, class T = void> using enable_if_t = typename std::enable_if<E, T>::type; template <bool B, class T, class F> using conditional_t = typename std::conditional<B, T, F>::type; // std::conjunction from C++17 template <class...> struct conjunction : std::true_type {}; template <class B> struct conjunction<B> : B {}; template <class B, class... Bs> struct conjunction<B, Bs...> : std::conditional<bool(B::value), conjunction<Bs...>, B>::type {}; #if defined(_LIBCPP_VERSION) && __cplusplus == 201103L #define TL_OPTIONAL_LIBCXX_MEM_FN_WORKAROUND #endif // In C++11 mode, there's an issue in libc++'s std::mem_fn // which results in a hard-error when using it in a noexcept expression // in some cases. This is a check to workaround the common failing case. #ifdef TL_OPTIONAL_LIBCXX_MEM_FN_WORKAROUND template <class T> struct is_pointer_to_non_const_member_func : std::false_type {}; template <class T, class Ret, class... Args> struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...)> : std::true_type {}; template <class T, class Ret, class... Args> struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) &> : std::true_type {}; template <class T, class Ret, class... Args> struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) &&> : std::true_type {}; template <class T, class Ret, class... Args> struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) volatile> : std::true_type {}; template <class T, class Ret, class... Args> struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) volatile &> : std::true_type {}; template <class T, class Ret, class... Args> struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) volatile &&> : std::true_type {}; template <class T> struct is_const_or_const_ref : std::false_type {}; template <class T> struct is_const_or_const_ref<T const &> : std::true_type {}; template <class T> struct is_const_or_const_ref<T const> : std::true_type {}; #endif // std::invoke from C++17 // https://stackoverflow.com/questions/38288042/c11-14-invoke-workaround template < typename Fn, typename... Args, #ifdef TL_OPTIONAL_LIBCXX_MEM_FN_WORKAROUND typename = enable_if_t<!(is_pointer_to_non_const_member_func<Fn>::value && is_const_or_const_ref<Args...>::value)>, #endif typename = enable_if_t<std::is_member_pointer<decay_t<Fn>>::value>, int = 0> constexpr auto invoke(Fn &&f, Args &&...args) noexcept( noexcept(std::mem_fn(f)(std::forward<Args>(args)...))) -> decltype(std::mem_fn(f)(std::forward<Args>(args)...)) { return std::mem_fn(f)(std::forward<Args>(args)...); } template <typename Fn, typename... Args, typename = enable_if_t<!std::is_member_pointer<decay_t<Fn>>::value>> constexpr auto invoke(Fn &&f, Args &&...args) noexcept( noexcept(std::forward<Fn>(f)(std::forward<Args>(args)...))) -> decltype(std::forward<Fn>(f)(std::forward<Args>(args)...)) { return std::forward<Fn>(f)(std::forward<Args>(args)...); } // std::invoke_result from C++17 template <class F, class, class... Us> struct invoke_result_impl; template <class F, class... Us> struct invoke_result_impl< F, decltype(detail::invoke(std::declval<F>(), std::declval<Us>()...), void()), Us...> { using type = decltype(detail::invoke(std::declval<F>(), std::declval<Us>()...)); }; template <class F, class... Us> using invoke_result = invoke_result_impl<F, void, Us...>; template <class F, class... Us> using invoke_result_t = typename invoke_result<F, Us...>::type; #if defined(_MSC_VER) && _MSC_VER <= 1900 // TODO make a version which works with MSVC 2015 template <class T, class U = T> struct is_swappable : std::true_type {}; template <class T, class U = T> struct is_nothrow_swappable : std::true_type {}; #else // https://stackoverflow.com/questions/26744589/what-is-a-proper-way-to-implement-is-swappable-to-test-for-the-swappable-concept namespace swap_adl_tests { // if swap ADL finds this then it would call std::swap otherwise (same // signature) struct tag {}; template <class T> tag swap(T &, T &); template <class T, std::size_t N> tag swap(T (&a)[N], T (&b)[N]); // helper functions to test if an unqualified swap is possible, and if it // becomes std::swap template <class, class> std::false_type can_swap(...) noexcept(false); template <class T, class U, class = decltype(swap(std::declval<T &>(), std::declval<U &>()))> std::true_type can_swap(int) noexcept(noexcept(swap(std::declval<T &>(), std::declval<U &>()))); template <class, class> std::false_type uses_std(...); template <class T, class U> std::is_same<decltype(swap(std::declval<T &>(), std::declval<U &>())), tag> uses_std(int); template <class T> struct is_std_swap_noexcept : std::integral_constant<bool, std::is_nothrow_move_constructible<T>::value && std::is_nothrow_move_assignable<T>::value> {}; template <class T, std::size_t N> struct is_std_swap_noexcept<T[N]> : is_std_swap_noexcept<T> {}; template <class T, class U> struct is_adl_swap_noexcept : std::integral_constant<bool, noexcept(can_swap<T, U>(0))> {}; } // namespace swap_adl_tests template <class T, class U = T> struct is_swappable : std::integral_constant< bool, decltype(detail::swap_adl_tests::can_swap<T, U>(0))::value && (!decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value || (std::is_move_assignable<T>::value && std::is_move_constructible<T>::value))> {}; template <class T, std::size_t N> struct is_swappable<T[N], T[N]> : std::integral_constant< bool, decltype(detail::swap_adl_tests::can_swap<T[N], T[N]>(0))::value && (!decltype( detail::swap_adl_tests::uses_std<T[N], T[N]>(0))::value || is_swappable<T, T>::value)> {}; template <class T, class U = T> struct is_nothrow_swappable : std::integral_constant< bool, is_swappable<T, U>::value && ((decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value &&detail::swap_adl_tests::is_std_swap_noexcept<T>::value) || (!decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value && detail::swap_adl_tests::is_adl_swap_noexcept<T, U>::value))> { }; #endif #endif // std::void_t from C++17 template <class...> struct voider { using type = void; }; template <class... Ts> using void_t = typename voider<Ts...>::type; // Trait for checking if a type is a tl::optional template <class T> struct is_optional_impl : std::false_type {}; template <class T> struct is_optional_impl<optional<T>> : std::true_type {}; template <class T> using is_optional = is_optional_impl<decay_t<T>>; // Change void to tl::monostate template <class U> using fixup_void = conditional_t<std::is_void<U>::value, monostate, U>; template <class F, class U, class = invoke_result_t<F, U>> using get_map_return = optional<fixup_void<invoke_result_t<F, U>>>; // Check if invoking F for some Us returns void template <class F, class = void, class... U> struct returns_void_impl; template <class F, class... U> struct returns_void_impl<F, void_t<invoke_result_t<F, U...>>, U...> : std::is_void<invoke_result_t<F, U...>> {}; template <class F, class... U> using returns_void = returns_void_impl<F, void, U...>; template <class T, class... U> using enable_if_ret_void = enable_if_t<returns_void<T &&, U...>::value>; template <class T, class... U> using disable_if_ret_void = enable_if_t<!returns_void<T &&, U...>::value>; template <class T, class U> using enable_forward_value = detail::enable_if_t<std::is_constructible<T, U &&>::value && !std::is_same<detail::decay_t<U>, in_place_t>::value && !std::is_same<optional<T>, detail::decay_t<U>>::value>; template <class T, class U, class Other> using enable_from_other = detail::enable_if_t< std::is_constructible<T, Other>::value && !std::is_constructible<T, optional<U> &>::value && !std::is_constructible<T, optional<U> &&>::value && !std::is_constructible<T, const optional<U> &>::value && !std::is_constructible<T, const optional<U> &&>::value && !std::is_convertible<optional<U> &, T>::value && !std::is_convertible<optional<U> &&, T>::value && !std::is_convertible<const optional<U> &, T>::value && !std::is_convertible<const optional<U> &&, T>::value>; template <class T, class U> using enable_assign_forward = detail::enable_if_t< !std::is_same<optional<T>, detail::decay_t<U>>::value && !detail::conjunction<std::is_scalar<T>, std::is_same<T, detail::decay_t<U>>>::value && std::is_constructible<T, U>::value && std::is_assignable<T &, U>::value>; template <class T, class U, class Other> using enable_assign_from_other = detail::enable_if_t< std::is_constructible<T, Other>::value && std::is_assignable<T &, Other>::value && !std::is_constructible<T, optional<U> &>::value && !std::is_constructible<T, optional<U> &&>::value && !std::is_constructible<T, const optional<U> &>::value && !std::is_constructible<T, const optional<U> &&>::value && !std::is_convertible<optional<U> &, T>::value && !std::is_convertible<optional<U> &&, T>::value && !std::is_convertible<const optional<U> &, T>::value && !std::is_convertible<const optional<U> &&, T>::value && !std::is_assignable<T &, optional<U> &>::value && !std::is_assignable<T &, optional<U> &&>::value && !std::is_assignable<T &, const optional<U> &>::value && !std::is_assignable<T &, const optional<U> &&>::value>; // The storage base manages the actual storage, and correctly propagates // trivial destruction from T. This case is for when T is not trivially // destructible. template <class T, bool = ::std::is_trivially_destructible<T>::value> struct optional_storage_base { TL_OPTIONAL_11_CONSTEXPR optional_storage_base() noexcept : m_dummy() {} template <class... U> TL_OPTIONAL_11_CONSTEXPR optional_storage_base(in_place_t, U &&...u) : m_value(std::forward<U>(u)...), m_hasValue(true) {} ~optional_storage_base() { if (m_hasValue) { m_value.~T(); m_hasValue = false; } } struct dummy {}; union { dummy m_dummy; T m_value; }; bool m_hasValue = false; }; // This case is for when T is trivially destructible. template <class T> struct optional_storage_base<T, true> { TL_OPTIONAL_11_CONSTEXPR optional_storage_base() noexcept : m_dummy() {} template <class... U> TL_OPTIONAL_11_CONSTEXPR optional_storage_base(in_place_t, U &&...u) : m_value(std::forward<U>(u)...), m_hasValue(true) {} // No destructor, so this class is trivially destructible struct dummy {}; union { dummy m_dummy; T m_value; }; bool m_hasValue = false; }; // This base class provides some handy member functions which can be used in // further derived classes template <class T> struct optional_operations_base : optional_storage_base<T> { using optional_storage_base<T>::optional_storage_base; void hard_reset() noexcept { get().~T(); this->m_hasValue = false; } template <class... Args> void construct(Args &&...args) noexcept { new (std::addressof(this->m_value)) T(std::forward<Args>(args)...); this->m_hasValue = true; } template <class Opt> void assign(Opt &&rhs) { if (this->hasValue()) { if (rhs.hasValue()) { this->m_value = std::forward<Opt>(rhs).get(); } else { this->m_value.~T(); this->m_hasValue = false; } } else if (rhs.hasValue()) { construct(std::forward<Opt>(rhs).get()); } } bool hasValue() const { return this->m_hasValue; } TL_OPTIONAL_11_CONSTEXPR T &get() & { return this->m_value; } TL_OPTIONAL_11_CONSTEXPR const T &get() const & { return this->m_value; } TL_OPTIONAL_11_CONSTEXPR T &&get() && { return std::move(this->m_value); } #ifndef TL_OPTIONAL_NO_CONSTRR constexpr const T &&get() const && { return std::move(this->m_value); } #endif }; // This class manages conditionally having a trivial copy constructor // This specialization is for when T is trivially copy constructible template <class T, bool = TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T)> struct optional_copy_base : optional_operations_base<T> { using optional_operations_base<T>::optional_operations_base; }; // This specialization is for when T is not trivially copy constructible template <class T> struct optional_copy_base<T, false> : optional_operations_base<T> { using optional_operations_base<T>::optional_operations_base; optional_copy_base() = default; optional_copy_base(const optional_copy_base &rhs) { if (rhs.hasValue()) { this->construct(rhs.get()); } else { this->m_hasValue = false; } } optional_copy_base(optional_copy_base &&rhs) = default; optional_copy_base &operator=(const optional_copy_base &rhs) = default; optional_copy_base &operator=(optional_copy_base &&rhs) = default; }; // This class manages conditionally having a trivial move constructor // Unfortunately there's no way to achieve this in GCC < 5 AFAIK, since it // doesn't implement an analogue to std::is_trivially_move_constructible. We // have to make do with a non-trivial move constructor even if T is trivially // move constructible #ifndef TL_OPTIONAL_GCC49 template <class T, bool = std::is_trivially_move_constructible<T>::value> struct optional_move_base : optional_copy_base<T> { using optional_copy_base<T>::optional_copy_base; }; #else template <class T, bool = false> struct optional_move_base; #endif template <class T> struct optional_move_base<T, false> : optional_copy_base<T> { using optional_copy_base<T>::optional_copy_base; optional_move_base() = default; optional_move_base(const optional_move_base &rhs) = default; optional_move_base(optional_move_base &&rhs) noexcept( std::is_nothrow_move_constructible<T>::value) { if (rhs.hasValue()) { this->construct(std::move(rhs.get())); } else { this->m_hasValue = false; } } optional_move_base &operator=(const optional_move_base &rhs) = default; optional_move_base &operator=(optional_move_base &&rhs) = default; }; // This class manages conditionally having a trivial copy assignment operator template <class T, bool = TL_OPTIONAL_IS_TRIVIALLY_COPY_ASSIGNABLE(T) && TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) && TL_OPTIONAL_IS_TRIVIALLY_DESTRUCTIBLE(T)> struct optional_copy_assign_base : optional_move_base<T> { using optional_move_base<T>::optional_move_base; }; template <class T> struct optional_copy_assign_base<T, false> : optional_move_base<T> { using optional_move_base<T>::optional_move_base; optional_copy_assign_base() = default; optional_copy_assign_base(const optional_copy_assign_base &rhs) = default; optional_copy_assign_base(optional_copy_assign_base &&rhs) = default; optional_copy_assign_base &operator=(const optional_copy_assign_base &rhs) { this->assign(rhs); return *this; } optional_copy_assign_base & operator=(optional_copy_assign_base &&rhs) = default; }; // This class manages conditionally having a trivial move assignment operator // Unfortunately there's no way to achieve this in GCC < 5 AFAIK, since it // doesn't implement an analogue to std::is_trivially_move_assignable. We have // to make do with a non-trivial move assignment operator even if T is trivially // move assignable #ifndef TL_OPTIONAL_GCC49 template <class T, bool = std::is_trivially_destructible<T>::value &&std::is_trivially_move_constructible<T>::value &&std::is_trivially_move_assignable<T>::value> struct optional_move_assign_base : optional_copy_assign_base<T> { using optional_copy_assign_base<T>::optional_copy_assign_base; }; #else template <class T, bool = false> struct optional_move_assign_base; #endif template <class T> struct optional_move_assign_base<T, false> : optional_copy_assign_base<T> { using optional_copy_assign_base<T>::optional_copy_assign_base; optional_move_assign_base() = default; optional_move_assign_base(const optional_move_assign_base &rhs) = default; optional_move_assign_base(optional_move_assign_base &&rhs) = default; optional_move_assign_base & operator=(const optional_move_assign_base &rhs) = default; optional_move_assign_base & operator=(optional_move_assign_base &&rhs) noexcept( std::is_nothrow_move_constructible<T>::value &&std::is_nothrow_move_assignable<T>::value) { this->assign(std::move(rhs)); return *this; } }; // optional_delete_ctor_base will conditionally delete copy and move // constructors depending on whether T is copy/move constructible template <class T, bool EnableCopy = std::is_copy_constructible<T>::value, bool EnableMove = std::is_move_constructible<T>::value> struct optional_delete_ctor_base { optional_delete_ctor_base() = default; optional_delete_ctor_base(const optional_delete_ctor_base &) = default; optional_delete_ctor_base(optional_delete_ctor_base &&) noexcept = default; optional_delete_ctor_base & operator=(const optional_delete_ctor_base &) = default; optional_delete_ctor_base & operator=(optional_delete_ctor_base &&) noexcept = default; }; template <class T> struct optional_delete_ctor_base<T, true, false> { optional_delete_ctor_base() = default; optional_delete_ctor_base(const optional_delete_ctor_base &) = default; optional_delete_ctor_base(optional_delete_ctor_base &&) noexcept = delete; optional_delete_ctor_base & operator=(const optional_delete_ctor_base &) = default; optional_delete_ctor_base & operator=(optional_delete_ctor_base &&) noexcept = default; }; template <class T> struct optional_delete_ctor_base<T, false, true> { optional_delete_ctor_base() = default; optional_delete_ctor_base(const optional_delete_ctor_base &) = delete; optional_delete_ctor_base(optional_delete_ctor_base &&) noexcept = default; optional_delete_ctor_base & operator=(const optional_delete_ctor_base &) = default; optional_delete_ctor_base & operator=(optional_delete_ctor_base &&) noexcept = default; }; template <class T> struct optional_delete_ctor_base<T, false, false> { optional_delete_ctor_base() = default; optional_delete_ctor_base(const optional_delete_ctor_base &) = delete; optional_delete_ctor_base(optional_delete_ctor_base &&) noexcept = delete; optional_delete_ctor_base & operator=(const optional_delete_ctor_base &) = default; optional_delete_ctor_base & operator=(optional_delete_ctor_base &&) noexcept = default; }; // optional_delete_assign_base will conditionally delete copy and move // constructors depending on whether T is copy/move constructible + assignable template <class T, bool EnableCopy = (std::is_copy_constructible<T>::value && std::is_copy_assignable<T>::value), bool EnableMove = (std::is_move_constructible<T>::value && std::is_move_assignable<T>::value)> struct optional_delete_assign_base { optional_delete_assign_base() = default; optional_delete_assign_base(const optional_delete_assign_base &) = default; optional_delete_assign_base(optional_delete_assign_base &&) noexcept = default; optional_delete_assign_base & operator=(const optional_delete_assign_base &) = default; optional_delete_assign_base & operator=(optional_delete_assign_base &&) noexcept = default; }; template <class T> struct optional_delete_assign_base<T, true, false> { optional_delete_assign_base() = default; optional_delete_assign_base(const optional_delete_assign_base &) = default; optional_delete_assign_base(optional_delete_assign_base &&) noexcept = default; optional_delete_assign_base & operator=(const optional_delete_assign_base &) = default; optional_delete_assign_base & operator=(optional_delete_assign_base &&) noexcept = delete; }; template <class T> struct optional_delete_assign_base<T, false, true> { optional_delete_assign_base() = default; optional_delete_assign_base(const optional_delete_assign_base &) = default; optional_delete_assign_base(optional_delete_assign_base &&) noexcept = default; optional_delete_assign_base & operator=(const optional_delete_assign_base &) = delete; optional_delete_assign_base & operator=(optional_delete_assign_base &&) noexcept = default; }; template <class T> struct optional_delete_assign_base<T, false, false> { optional_delete_assign_base() = default; optional_delete_assign_base(const optional_delete_assign_base &) = default; optional_delete_assign_base(optional_delete_assign_base &&) noexcept = default; optional_delete_assign_base & operator=(const optional_delete_assign_base &) = delete; optional_delete_assign_base & operator=(optional_delete_assign_base &&) noexcept = delete; }; } // namespace detail /// A tag type to represent an empty optional struct nullopt_t { struct do_not_use {}; constexpr explicit nullopt_t(do_not_use, do_not_use) noexcept {} }; /// Represents an empty optional static constexpr nullopt_t nullopt{nullopt_t::do_not_use{}, nullopt_t::do_not_use{}}; class bad_optional_access : public std::exception { public: bad_optional_access() = default; const char *what() const noexcept override { return "Optional has no value"; } }; namespace detail { struct i_am_secret {}; } // namespace detail template <class T = detail::i_am_secret, class U, class Ret = detail::conditional_t<std::is_same<T, detail::i_am_secret>::value, detail::decay_t<U>, T>> constexpr optional<Ret> make_optional(U &&v); /// An optional object is an object that contains the storage for another /// object and manages the lifetime of this contained object, if any. The /// contained object may be initialized after the optional object has been /// initialized, and may be destroyed before the optional object has been /// destroyed. The initialization state of the contained object is tracked by /// the optional object. template <class T> class optional : private detail::optional_move_assign_base<T>, private detail::optional_delete_ctor_base<T>, private detail::optional_delete_assign_base<T> { using base = detail::optional_move_assign_base<T>; static_assert(!std::is_same<T, in_place_t>::value, "instantiation of optional with in_place_t is ill-formed"); static_assert(!std::is_same<detail::decay_t<T>, nullopt_t>::value, "instantiation of optional with nullopt_t is ill-formed"); template <typename L, typename R> friend constexpr bool operator==(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator!=(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator<(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator>(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator<=(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator>=(const optional<L> &, const optional<R> &); // template <typename L, typename R> friend constexpr bool operator==(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator==(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator!=(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator!=(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator<(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator<(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator>(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator>(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator<=(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator<=(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator>=(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator>=(const R &, const optional<T> &); template <class Opt, class F, class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Opt>())), detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr> constexpr auto optional_map_impl(Opt &&opt, F &&f) { return opt.hasValue() ? detail::invoke(std::forward<F>(f), *std::forward<Opt>(opt)) : optional<Ret>(nullopt); } template <class Opt, class F, class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Opt>())), detail::enable_if_t<std::is_void<Ret>::value> * = nullptr> auto optional_map_impl(Opt &&opt, F &&f) { if (opt.hasValue()) { detail::invoke(std::forward<F>(f), *std::forward<Opt>(opt)); return make_optional(monostate{}); } return optional<monostate>(nullopt); } public: // The different versions for C++14 and 11 are needed because deduced return // types are not SFINAE-safe. This provides better support for things like // generic lambdas. C.f. // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0826r0.html #if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \ !defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55) /// Carries out some operation which returns an optional on the stored /// object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR auto flatMap(F &&f) & { using result = detail::invoke_result_t<F, T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } template <class F> TL_OPTIONAL_11_CONSTEXPR auto flatMap(F &&f) && { using result = detail::invoke_result_t<F, T &&>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : result(nullopt); } template <class F> constexpr auto flatMap(F &&f) const & { using result = detail::invoke_result_t<F, const T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F> constexpr auto flatMap(F &&f) const && { using result = detail::invoke_result_t<F, const T &&>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : result(nullopt); } #endif #else /// Carries out some operation which returns an optional on the stored /// object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR detail::invoke_result_t<F, T &> flatMap(F &&f) & { using result = detail::invoke_result_t<F, T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } template <class F> TL_OPTIONAL_11_CONSTEXPR detail::invoke_result_t<F, T &&> flatMap(F &&f) && { using result = detail::invoke_result_t<F, T &&>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : result(nullopt); } template <class F> constexpr detail::invoke_result_t<F, const T &> flatMap(F &&f) const & { using result = detail::invoke_result_t<F, const T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F> constexpr detail::invoke_result_t<F, const T &&> flatMap(F &&f) const && { using result = detail::invoke_result_t<F, const T &&>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : result(nullopt); } #endif #endif #if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \ !defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55) /// Carries out some operation on the stored object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR auto map(F &&f) & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> TL_OPTIONAL_11_CONSTEXPR auto map(F &&f) && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } template <class F> constexpr auto map(F &&f) const & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> constexpr auto map(F &&f) const && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } #else /// Carries out some operation on the stored object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR decltype( optional_map_impl(std::declval<optional &>(), std::declval<F &&>())) map(F &&f) & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> TL_OPTIONAL_11_CONSTEXPR decltype( optional_map_impl(std::declval<optional &&>(), std::declval<F &&>())) map(F &&f) && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } template <class F> constexpr decltype(optional_map_impl(std::declval<const optional &>(), std::declval<F &&>())) map(F &&f) const & { return optional_map_impl(*this, std::forward<F>(f)); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F> constexpr decltype(optional_map_impl(std::declval<const optional &&>(), std::declval<F &&>())) map(F &&f) const && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } #endif #endif #if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \ !defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55) /// Carries out some operation on the stored object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR auto transform(F &&f) & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> TL_OPTIONAL_11_CONSTEXPR auto transform(F &&f) && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } template <class F> constexpr auto transform(F &&f) const & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> constexpr auto transform(F &&f) const && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } #else /// Carries out some operation on the stored object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR decltype( optional_map_impl(std::declval<optional &>(), std::declval<F &&>())) transform(F &&f) & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> TL_OPTIONAL_11_CONSTEXPR decltype( optional_map_impl(std::declval<optional &&>(), std::declval<F &&>())) transform(F &&f) && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } template <class F> constexpr decltype(optional_map_impl(std::declval<const optional &>(), std::declval<F &&>())) transform(F &&f) const & { return optional_map_impl(*this, std::forward<F>(f)); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F> constexpr decltype(optional_map_impl(std::declval<const optional &&>(), std::declval<F &&>())) transform(F &&f) const && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } #endif #endif /// Calls `f` if the optional is empty template <class F, detail::enable_if_ret_void<F> * = nullptr> optional<T> TL_OPTIONAL_11_CONSTEXPR orElse(F &&f) & { if (hasValue()) return *this; std::forward<F>(f)(); return nullopt; } template <class F, detail::disable_if_ret_void<F> * = nullptr> optional<T> TL_OPTIONAL_11_CONSTEXPR orElse(F &&f) & { return hasValue() ? *this : std::forward<F>(f)(); } template <class F, detail::enable_if_ret_void<F> * = nullptr> optional<T> orElse(F &&f) && { if (hasValue()) return std::move(*this); std::forward<F>(f)(); return nullopt; } template <class F, detail::disable_if_ret_void<F> * = nullptr> optional<T> TL_OPTIONAL_11_CONSTEXPR orElse(F &&f) && { return hasValue() ? std::move(*this) : std::forward<F>(f)(); } template <class F, detail::enable_if_ret_void<F> * = nullptr> optional<T> orElse(F &&f) const & { if (hasValue()) return *this; std::forward<F>(f)(); return nullopt; } template <class F, detail::disable_if_ret_void<F> * = nullptr> optional<T> TL_OPTIONAL_11_CONSTEXPR orElse(F &&f) const & { return hasValue() ? *this : std::forward<F>(f)(); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F, detail::enable_if_ret_void<F> * = nullptr> optional<T> orElse(F &&f) const && { if (hasValue()) return std::move(*this); std::forward<F>(f)(); return nullopt; } template <class F, detail::disable_if_ret_void<F> * = nullptr> optional<T> orElse(F &&f) const && { return hasValue() ? std::move(*this) : std::forward<F>(f)(); } #endif /// Maps the stored value with `f` if there is one, otherwise returns `u`. template <class F, class U> U mapOr(F &&f, U &&u) & { return hasValue() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u); } template <class F, class U> U mapOr(F &&f, U &&u) && { return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : std::forward<U>(u); } template <class F, class U> U mapOr(F &&f, U &&u) const & { return hasValue() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F, class U> U mapOr(F &&f, U &&u) const && { return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : std::forward<U>(u); } #endif template <class P> auto filter(P &&p) & { return mapOr(std::forward<P>(p), false) ? *this : nullopt; } template <class P> auto filter(P &&p) && { return mapOr(std::forward<P>(p), false) ? std::move(*this) : nullopt; } template <class P> auto filter(P &&p) const & { return mapOr(std::forward<P>(p), false) ? *this : nullopt; } #ifndef TL_OPTIONAL_NO_CONSTRR template <class P> optional<T> filter(P &&p) const && { return mapOr(std::forward<P>(p), false) ? std::move(*this) : nullopt; } #endif /// Maps the stored value with `f` if there is one, otherwise calls /// `u` and returns the result. template <class F, class U> detail::invoke_result_t<U> mapOrElse(F &&f, U &&u) & { return hasValue() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u)(); } template <class F, class U> detail::invoke_result_t<U> mapOrElse(F &&f, U &&u) && { return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : std::forward<U>(u)(); } template <class F, class U> detail::invoke_result_t<U> mapOrElse(F &&f, U &&u) const & { return hasValue() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u)(); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F, class U> detail::invoke_result_t<U> mapOrElse(F &&f, U &&u) const && { return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : std::forward<U>(u)(); } #endif /// Predicate: check if optional's value equals the given one. template <class F> constexpr bool containsValue(F &&f) & { return hasValue() ? *this == f : false; } template <class F> constexpr bool containsValue(F &&f) && { return hasValue() ? std::move(**this) == f : false; } template <class F> constexpr bool containsValue(F &&f) const & { return hasValue() ? *this == f : false; } template <class F> constexpr bool containsValue(F &&f) const && { return hasValue() ? std::move(**this) == f : false; } /// Returns `u` if `*this` has a value, otherwise an empty optional. template <class U> constexpr optional<typename std::decay<U>::type> conjunction(U &&u) const { using result = optional<detail::decay_t<U>>; return hasValue() ? result{u} : result{nullopt}; } /// Returns `rhs` if `*this` is empty, otherwise the current value. TL_OPTIONAL_11_CONSTEXPR optional disjunction(const optional &rhs) & { return hasValue() ? *this : rhs; } constexpr optional disjunction(const optional &rhs) const & { return hasValue() ? *this : rhs; } TL_OPTIONAL_11_CONSTEXPR optional disjunction(const optional &rhs) && { return hasValue() ? std::move(*this) : rhs; } #ifndef TL_OPTIONAL_NO_CONSTRR constexpr optional disjunction(const optional &rhs) const && { return hasValue() ? std::move(*this) : rhs; } #endif TL_OPTIONAL_11_CONSTEXPR optional disjunction(optional &&rhs) & { return hasValue() ? *this : std::move(rhs); } constexpr optional disjunction(optional &&rhs) const & { return hasValue() ? *this : std::move(rhs); } TL_OPTIONAL_11_CONSTEXPR optional disjunction(optional &&rhs) && { return hasValue() ? std::move(*this) : std::move(rhs); } #ifndef TL_OPTIONAL_NO_CONSTRR constexpr optional disjunction(optional &&rhs) const && { return hasValue() ? std::move(*this) : std::move(rhs); } #endif /// Takes the value out of the optional, leaving it empty optional take() { optional ret = std::move(*this); reset(); return ret; } using value_type = T; /// Constructs an optional that does not contain a value. constexpr optional() noexcept = default; constexpr optional(nullopt_t) noexcept {} /// Copy constructor /// /// If `rhs` contains a value, the stored value is direct-initialized with /// it. Otherwise, the constructed optional is empty. TL_OPTIONAL_11_CONSTEXPR optional(const optional &rhs) = default; /// Move constructor /// /// If `rhs` contains a value, the stored value is direct-initialized with /// it. Otherwise, the constructed optional is empty. TL_OPTIONAL_11_CONSTEXPR optional(optional &&rhs) = default; /// Constructs the stored value in-place using the given arguments. template <class... Args> constexpr explicit optional( detail::enable_if_t<std::is_constructible<T, Args...>::value, in_place_t>, Args &&...args) : base(in_place, std::forward<Args>(args)...) {} template <class U, class... Args> TL_OPTIONAL_11_CONSTEXPR explicit optional( detail::enable_if_t<std::is_constructible<T, std::initializer_list<U> &, Args &&...>::value, in_place_t>, std::initializer_list<U> il, Args &&...args) { this->construct(il, std::forward<Args>(args)...); } /// Constructs the stored value with `u`. template < class U = T, detail::enable_if_t<std::is_convertible<U &&, T>::value> * = nullptr, detail::enable_forward_value<T, U> * = nullptr> constexpr optional(U &&u) : base(in_place, std::forward<U>(u)) {} template < class U = T, detail::enable_if_t<!std::is_convertible<U &&, T>::value> * = nullptr, detail::enable_forward_value<T, U> * = nullptr> constexpr explicit optional(U &&u) : base(in_place, std::forward<U>(u)) {} /// Converting copy constructor. template < class U, detail::enable_from_other<T, U, const U &> * = nullptr, detail::enable_if_t<std::is_convertible<const U &, T>::value> * = nullptr> optional(const optional<U> &rhs) { if (rhs.hasValue()) { this->construct(*rhs); } } template <class U, detail::enable_from_other<T, U, const U &> * = nullptr, detail::enable_if_t<!std::is_convertible<const U &, T>::value> * = nullptr> explicit optional(const optional<U> &rhs) { if (rhs.hasValue()) { this->construct(*rhs); } } /// Converting move constructor. template < class U, detail::enable_from_other<T, U, U &&> * = nullptr, detail::enable_if_t<std::is_convertible<U &&, T>::value> * = nullptr> optional(optional<U> &&rhs) { if (rhs.hasValue()) { this->construct(std::move(*rhs)); } } template < class U, detail::enable_from_other<T, U, U &&> * = nullptr, detail::enable_if_t<!std::is_convertible<U &&, T>::value> * = nullptr> explicit optional(optional<U> &&rhs) { if (rhs.hasValue()) { this->construct(std::move(*rhs)); } } /// Destroys the stored value if there is one. ~optional() = default; /// Assignment to empty. /// /// Destroys the current value if there is one. optional &operator=(nullopt_t) noexcept { if (hasValue()) { this->m_value.~T(); this->m_hasValue = false; } return *this; } /// Copy assignment. /// /// Copies the value from `rhs` if there is one. Otherwise resets the stored /// value in `*this`. optional &operator=(const optional &rhs) = default; /// Move assignment. /// /// Moves the value from `rhs` if there is one. Otherwise resets the stored /// value in `*this`. optional &operator=(optional &&rhs) = default; /// Assigns the stored value from `u`, destroying the old value if there was /// one. template <class U = T, detail::enable_assign_forward<T, U> * = nullptr> optional &operator=(U &&u) { if (hasValue()) { this->m_value = std::forward<U>(u); } else { this->construct(std::forward<U>(u)); } return *this; } /// Converting copy assignment operator. /// /// Copies the value from `rhs` if there is one. Otherwise resets the stored /// value in `*this`. template <class U, detail::enable_assign_from_other<T, U, const U &> * = nullptr> optional &operator=(const optional<U> &rhs) { if (hasValue()) { if (rhs.hasValue()) { this->m_value = *rhs; } else { this->hard_reset(); } } if (rhs.hasValue()) { this->construct(*rhs); } return *this; } // TODO check exception guarantee /// Converting move assignment operator. /// /// Moves the value from `rhs` if there is one. Otherwise resets the stored /// value in `*this`. template <class U, detail::enable_assign_from_other<T, U, U> * = nullptr> optional &operator=(optional<U> &&rhs) { if (hasValue()) { if (rhs.hasValue()) { this->m_value = std::move(*rhs); } else { this->hard_reset(); } } if (rhs.hasValue()) { this->construct(std::move(*rhs)); } return *this; } /// Constructs the value in-place, destroying the current one if there is /// one. template <class... Args> T &emplace(Args &&...args) { static_assert(std::is_constructible<T, Args &&...>::value, "T must be constructible with Args"); *this = nullopt; this->construct(std::forward<Args>(args)...); return value(); } template <class U, class... Args> detail::enable_if_t< std::is_constructible<T, std::initializer_list<U> &, Args &&...>::value, T &> emplace(std::initializer_list<U> il, Args &&...args) { *this = nullopt; this->construct(il, std::forward<Args>(args)...); return value(); } /// Swaps this optional with the other. /// /// If neither optionals have a value, nothing happens. /// If both have a value, the values are swapped. /// If one has a value, it is moved to the other and the movee is left /// valueless. void swap(optional &rhs) noexcept(std::is_nothrow_move_constructible<T>::value &&detail::is_nothrow_swappable<T>::value) { if (hasValue()) { if (rhs.hasValue()) { using std::swap; swap(**this, *rhs); } else { new (std::addressof(rhs.m_value)) T(std::move(this->m_value)); this->m_value.T::~T(); } } else if (rhs.hasValue()) { new (std::addressof(this->m_value)) T(std::move(rhs.m_value)); rhs.m_value.T::~T(); } } /// Returns whether or not the optional has a value constexpr bool hasValue() const noexcept { return this->m_hasValue; } constexpr explicit operator bool() const noexcept { return this->m_hasValue; } /// Returns a pointer to the stored value private: constexpr const T *operator->() const { return std::addressof(this->m_value); } TL_OPTIONAL_11_CONSTEXPR T *operator->() { return std::addressof(this->m_value); } /// Returns the stored value TL_OPTIONAL_11_CONSTEXPR T &operator*() & { return this->m_value; } constexpr const T &operator*() const & { return this->m_value; } TL_OPTIONAL_11_CONSTEXPR T &&operator*() && { return std::move(this->m_value); } #ifndef TL_OPTIONAL_NO_CONSTRR constexpr const T &&operator*() const && { return std::move(this->m_value); } #endif /// Returns the contained value if there is one, otherwise throws /// bad_optional_access TL_OPTIONAL_11_CONSTEXPR T &value() & { if (hasValue()) return this->m_value; throw bad_optional_access(); } TL_OPTIONAL_11_CONSTEXPR const T &value() const & { if (hasValue()) return this->m_value; throw bad_optional_access(); } TL_OPTIONAL_11_CONSTEXPR T &&value() && { if (hasValue()) return std::move(this->m_value); throw bad_optional_access(); } #ifndef TL_OPTIONAL_NO_CONSTRR TL_OPTIONAL_11_CONSTEXPR const T &&value() const && { if (hasValue()) return std::move(this->m_value); throw bad_optional_access(); } #endif public: /// Returns the stored value if there is one, otherwise returns `u` template <class U> constexpr T getOr(U &&u) const & { static_assert(std::is_copy_constructible<T>::value && std::is_convertible<U &&, T>::value, "T must be copy constructible and convertible from U"); return hasValue() ? **this : static_cast<T>(std::forward<U>(u)); } template <class U> TL_OPTIONAL_11_CONSTEXPR T getOr(U &&u) && { static_assert(std::is_move_constructible<T>::value && std::is_convertible<U &&, T>::value, "T must be move constructible and convertible from U"); return hasValue() ? **this : static_cast<T>(std::forward<U>(u)); } /// Destroys the stored value if one exists, making the optional empty void reset() noexcept { if (hasValue()) { this->m_value.~T(); this->m_hasValue = false; } } }; // namespace tl /// Compares two optional objects template <class T, class U> inline constexpr bool operator==(const optional<T> &lhs, const optional<U> &rhs) { return lhs.hasValue() == rhs.hasValue() && (!lhs.hasValue() || *lhs == *rhs); } template <class T, class U> inline constexpr bool operator!=(const optional<T> &lhs, const optional<U> &rhs) { return lhs.hasValue() != rhs.hasValue() || (lhs.hasValue() && *lhs != *rhs); } template <class T, class U> inline constexpr bool operator<(const optional<T> &lhs, const optional<U> &rhs) { return rhs.hasValue() && (!lhs.hasValue() || *lhs < *rhs); } template <class T, class U> inline constexpr bool operator>(const optional<T> &lhs, const optional<U> &rhs) { return lhs.hasValue() && (!rhs.hasValue() || *lhs > *rhs); } template <class T, class U> inline constexpr bool operator<=(const optional<T> &lhs, const optional<U> &rhs) { return !lhs.hasValue() || (rhs.hasValue() && *lhs <= *rhs); } template <class T, class U> inline constexpr bool operator>=(const optional<T> &lhs, const optional<U> &rhs) { return !rhs.hasValue() || (lhs.hasValue() && *lhs >= *rhs); } /// Compares an optional to a `nullopt` template <class T> inline constexpr bool operator==(const optional<T> &lhs, nullopt_t) noexcept { return !lhs.hasValue(); } template <class T> inline constexpr bool operator==(nullopt_t, const optional<T> &rhs) noexcept { return !rhs.hasValue(); } template <class T> inline constexpr bool operator!=(const optional<T> &lhs, nullopt_t) noexcept { return lhs.hasValue(); } template <class T> inline constexpr bool operator!=(nullopt_t, const optional<T> &rhs) noexcept { return rhs.hasValue(); } template <class T> inline constexpr bool operator<(const optional<T> &, nullopt_t) noexcept { return false; } template <class T> inline constexpr bool operator<(nullopt_t, const optional<T> &rhs) noexcept { return rhs.hasValue(); } template <class T> inline constexpr bool operator<=(const optional<T> &lhs, nullopt_t) noexcept { return !lhs.hasValue(); } template <class T> inline constexpr bool operator<=(nullopt_t, const optional<T> &) noexcept { return true; } template <class T> inline constexpr bool operator>(const optional<T> &lhs, nullopt_t) noexcept { return lhs.hasValue(); } template <class T> inline constexpr bool operator>(nullopt_t, const optional<T> &) noexcept { return false; } template <class T> inline constexpr bool operator>=(const optional<T> &, nullopt_t) noexcept { return true; } template <class T> inline constexpr bool operator>=(nullopt_t, const optional<T> &rhs) noexcept { return !rhs.hasValue(); } /// Compares the optional with a value. template <class T, class U> inline constexpr bool operator==(const optional<T> &lhs, const U &rhs) { return lhs.filter([&rhs](const auto value) { return value == rhs; }) .hasValue(); } template <class T, class U> inline constexpr bool operator==(const U &lhs, const optional<T> &rhs) { return rhs == lhs; } template <class T, class U> inline constexpr bool operator!=(const optional<T> &lhs, const U &rhs) { return !(lhs == rhs); } template <class T, class U> inline constexpr bool operator!=(const U &lhs, const optional<T> &rhs) { return !(lhs == rhs); } template <class T, class U> inline constexpr bool operator<(const optional<T> &lhs, const U &rhs) { return lhs.filter([&rhs](const auto value) { return value < rhs; }) .hasValue(); } template <class T, class U> inline constexpr bool operator<(const U &lhs, const optional<T> &rhs) { return rhs.filter([&lhs](const auto value) { return lhs < value; }) .hasValue(); } template <class T, class U> inline constexpr bool operator>(const optional<T> &lhs, const U &rhs) { return lhs.filter([&rhs](const auto value) { return value > rhs; }) .hasValue(); } template <class T, class U> inline constexpr bool operator>(const U &lhs, const optional<T> &rhs) { return rhs.filter([&lhs](const auto value) { return lhs > value; }) .hasValue(); } template <class T, class U> inline constexpr bool operator<=(const optional<T> &lhs, const U &rhs) { return !(lhs > rhs); } template <class T, class U> inline constexpr bool operator<=(const U &lhs, const optional<T> &rhs) { return !(lhs > rhs); } template <class T, class U> inline constexpr bool operator>=(const optional<T> &lhs, const U &rhs) { return !(lhs < rhs); } template <class T, class U> inline constexpr bool operator>=(const U &lhs, const optional<T> &rhs) { return !(lhs < rhs); } template <class T, detail::enable_if_t<std::is_move_constructible<T>::value> * = nullptr, detail::enable_if_t<detail::is_swappable<T>::value> * = nullptr> void swap(optional<T> &lhs, optional<T> &rhs) noexcept(noexcept(lhs.swap(rhs))) { return lhs.swap(rhs); } template <class T, class U, class Ret> inline constexpr optional<Ret> make_optional(U &&v) { return optional<Ret>(std::forward<U>(v)); } template <class T, class... Args> inline constexpr optional<T> make_optional(Args &&...args) { return optional<T>(in_place, std::forward<Args>(args)...); } template <class T, class U, class... Args> inline constexpr optional<T> make_optional(std::initializer_list<U> il, Args &&...args) { return optional<T>(in_place, il, std::forward<Args>(args)...); } #if __cplusplus >= 201703L template <class T> optional(T) -> optional<T>; #endif /// Specialization for when `T` is a reference. `optional<T&>` acts similarly /// to a `T*`, but provides more operations and shows intent more clearly. template <class T> class optional<T &> { template <typename L, typename R> friend constexpr bool operator==(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator!=(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator<(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator>(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator<=(const optional<L> &, const optional<R> &); template <typename L, typename R> friend constexpr bool operator>=(const optional<L> &, const optional<R> &); // template <typename L, typename R> friend constexpr bool operator==(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator==(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator!=(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator!=(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator<(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator<(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator>(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator>(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator<=(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator<=(const R &, const optional<T> &); template <typename L, typename R> friend constexpr bool operator>=(const optional<T> &, const R &); template <typename L, typename R> friend constexpr bool operator>=(const R &, const optional<T> &); template <class Opt, class F, class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Opt>())), detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr> constexpr auto optional_map_impl(Opt &&opt, F &&f) { return opt.hasValue() ? detail::invoke(std::forward<F>(f), *std::forward<Opt>(opt)) : optional<Ret>(nullopt); } template <class Opt, class F, class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Opt>())), detail::enable_if_t<std::is_void<Ret>::value> * = nullptr> auto optional_map_impl(Opt &&opt, F &&f) { if (opt.hasValue()) { detail::invoke(std::forward<F>(f), *std::forward<Opt>(opt)); return make_optional(monostate{}); } return optional<monostate>(nullopt); } public: // The different versions for C++14 and 11 are needed because deduced return // types are not SFINAE-safe. This provides better support for things like // generic lambdas. C.f. // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0826r0.html #if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \ !defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55) /// Carries out some operation which returns an optional on the stored /// object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR auto flatMap(F &&f) & { using result = detail::invoke_result_t<F, T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } template <class F> TL_OPTIONAL_11_CONSTEXPR auto flatMap(F &&f) && { using result = detail::invoke_result_t<F, T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } template <class F> constexpr auto flatMap(F &&f) const & { using result = detail::invoke_result_t<F, const T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F> constexpr auto flatMap(F &&f) const && { using result = detail::invoke_result_t<F, const T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } #endif #else /// Carries out some operation which returns an optional on the stored /// object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR detail::invoke_result_t<F, T &> flatMap(F &&f) & { using result = detail::invoke_result_t<F, T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } template <class F> TL_OPTIONAL_11_CONSTEXPR detail::invoke_result_t<F, T &> flatMap(F &&f) && { using result = detail::invoke_result_t<F, T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } template <class F> constexpr detail::invoke_result_t<F, const T &> flatMap(F &&f) const & { using result = detail::invoke_result_t<F, const T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F> constexpr detail::invoke_result_t<F, const T &> flatMap(F &&f) const && { using result = detail::invoke_result_t<F, const T &>; static_assert(detail::is_optional<result>::value, "F must return an optional"); return hasValue() ? detail::invoke(std::forward<F>(f), **this) : result(nullopt); } #endif #endif #if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \ !defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55) /// Carries out some operation on the stored object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR auto map(F &&f) & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> TL_OPTIONAL_11_CONSTEXPR auto map(F &&f) && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } template <class F> constexpr auto map(F &&f) const & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> constexpr auto map(F &&f) const && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } #else /// Carries out some operation on the stored object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR decltype(detail::optional_map_impl( std::declval<optional &>(), std::declval<F &&>())) map(F &&f) & { return detail::optional_map_impl(*this, std::forward<F>(f)); } template <class F> TL_OPTIONAL_11_CONSTEXPR decltype(detail::optional_map_impl( std::declval<optional &&>(), std::declval<F &&>())) map(F &&f) && { return detail::optional_map_impl(std::move(*this), std::forward<F>(f)); } template <class F> constexpr decltype(detail::optional_map_impl(std::declval<const optional &>(), std::declval<F &&>())) map(F &&f) const & { return detail::optional_map_impl(*this, std::forward<F>(f)); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F> constexpr decltype(detail::optional_map_impl( std::declval<const optional &&>(), std::declval<F &&>())) map(F &&f) const && { return detail::optional_map_impl(std::move(*this), std::forward<F>(f)); } #endif #endif #if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \ !defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55) /// Carries out some operation on the stored object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR auto transform(F &&f) & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> TL_OPTIONAL_11_CONSTEXPR auto transform(F &&f) && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } template <class F> constexpr auto transform(F &&f) const & { return optional_map_impl(*this, std::forward<F>(f)); } template <class F> constexpr auto transform(F &&f) const && { return optional_map_impl(std::move(*this), std::forward<F>(f)); } #else /// Carries out some operation on the stored object if there is one. template <class F> TL_OPTIONAL_11_CONSTEXPR decltype(detail::optional_map_impl( std::declval<optional &>(), std::declval<F &&>())) transform(F &&f) & { return detail::optional_map_impl(*this, std::forward<F>(f)); } /// \group map /// \synopsis template <class F> auto transform(F &&f) &&; template <class F> TL_OPTIONAL_11_CONSTEXPR decltype(detail::optional_map_impl( std::declval<optional &&>(), std::declval<F &&>())) transform(F &&f) && { return detail::optional_map_impl(std::move(*this), std::forward<F>(f)); } template <class F> constexpr decltype(detail::optional_map_impl(std::declval<const optional &>(), std::declval<F &&>())) transform(F &&f) const & { return detail::optional_map_impl(*this, std::forward<F>(f)); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F> constexpr decltype(detail::optional_map_impl( std::declval<const optional &&>(), std::declval<F &&>())) transform(F &&f) const && { return detail::optional_map_impl(std::move(*this), std::forward<F>(f)); } #endif #endif /// Calls `f` if the optional is empty template <class F, detail::enable_if_ret_void<F> * = nullptr> optional<T &> TL_OPTIONAL_11_CONSTEXPR orElse(F &&f) & { if (hasValue()) return *this; std::forward<F>(f)(); return nullopt; } template <class F, detail::disable_if_ret_void<F> * = nullptr> optional<T &> TL_OPTIONAL_11_CONSTEXPR orElse(F &&f) & { return hasValue() ? *this : std::forward<F>(f)(); } template <class F, detail::enable_if_ret_void<F> * = nullptr> optional<T &> orElse(F &&f) && { if (hasValue()) return std::move(*this); std::forward<F>(f)(); return nullopt; } template <class F, detail::disable_if_ret_void<F> * = nullptr> optional<T &> TL_OPTIONAL_11_CONSTEXPR orElse(F &&f) && { return hasValue() ? std::move(*this) : std::forward<F>(f)(); } template <class F, detail::enable_if_ret_void<F> * = nullptr> optional<T &> orElse(F &&f) const & { if (hasValue()) return *this; std::forward<F>(f)(); return nullopt; } template <class F, detail::disable_if_ret_void<F> * = nullptr> optional<T &> TL_OPTIONAL_11_CONSTEXPR orElse(F &&f) const & { return hasValue() ? *this : std::forward<F>(f)(); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F, detail::enable_if_ret_void<F> * = nullptr> optional<T &> orElse(F &&f) const && { if (hasValue()) return std::move(*this); std::forward<F>(f)(); return nullopt; } template <class F, detail::disable_if_ret_void<F> * = nullptr> optional<T &> orElse(F &&f) const && { return hasValue() ? std::move(*this) : std::forward<F>(f)(); } #endif /// Maps the stored value with `f` if there is one, otherwise returns `u` template <class F, class U> U mapOr(F &&f, U &&u) & { return hasValue() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u); } template <class F, class U> U mapOr(F &&f, U &&u) && { return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : std::forward<U>(u); } template <class F, class U> U mapOr(F &&f, U &&u) const & { return hasValue() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F, class U> U mapOr(F &&f, U &&u) const && { return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : std::forward<U>(u); } #endif template <class P> auto filter(P &&p) & { return mapOr(std::forward<P>(p), false) ? *this : nullopt; } template <class P> auto filter(P &&p) && { return mapOr(std::forward<P>(p), false) ? std::move(*this) : nullopt; } template <class P> auto filter(P &&p) const & { return mapOr(std::forward<P>(p), false) ? *this : nullopt; } #ifndef TL_OPTIONAL_NO_CONSTRR template <class P> optional<T> filter(P &&p) const && { return mapOr(std::forward<P>(p), false) ? std::move(*this) : nullopt; } #endif /// Predicate: check if optional's value equals the given one. template <class F> constexpr bool containsValue(F &&f) & { return hasValue() ? *this == f : false; } template <class F> constexpr bool containsValue(F &&f) && { return hasValue() ? std::move(**this) == f : false; } template <class F> constexpr bool containsValue(F &&f) const & { return hasValue() ? *this == f : false; } template <class F> constexpr bool containsValue(F &&f) const && { return hasValue() ? std::move(**this) == f : false; } /// Maps the stored value with `f` if there is one, otherwise calls /// `u` and returns the result. template <class F, class U> detail::invoke_result_t<U> mapOrElse(F &&f, U &&u) & { return hasValue() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u)(); } template <class F, class U> detail::invoke_result_t<U> mapOrElse(F &&f, U &&u) && { return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : std::forward<U>(u)(); } template <class F, class U> detail::invoke_result_t<U> mapOrElse(F &&f, U &&u) const & { return hasValue() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u)(); } #ifndef TL_OPTIONAL_NO_CONSTRR template <class F, class U> detail::invoke_result_t<U> mapOrElse(F &&f, U &&u) const && { return hasValue() ? detail::invoke(std::forward<F>(f), std::move(**this)) : std::forward<U>(u)(); } #endif /// Returns `u` if `*this` has a value, otherwise an empty optional. template <class U> constexpr optional<typename std::decay<U>::type> conjunction(U &&u) const { using result = optional<detail::decay_t<U>>; return hasValue() ? result{u} : result{nullopt}; } /// Returns `rhs` if `*this` is empty, otherwise the current value. TL_OPTIONAL_11_CONSTEXPR optional disjunction(const optional &rhs) & { return hasValue() ? *this : rhs; } constexpr optional disjunction(const optional &rhs) const & { return hasValue() ? *this : rhs; } TL_OPTIONAL_11_CONSTEXPR optional disjunction(const optional &rhs) && { return hasValue() ? std::move(*this) : rhs; } #ifndef TL_OPTIONAL_NO_CONSTRR constexpr optional disjunction(const optional &rhs) const && { return hasValue() ? std::move(*this) : rhs; } #endif TL_OPTIONAL_11_CONSTEXPR optional disjunction(optional &&rhs) & { return hasValue() ? *this : std::move(rhs); } constexpr optional disjunction(optional &&rhs) const & { return hasValue() ? *this : std::move(rhs); } TL_OPTIONAL_11_CONSTEXPR optional disjunction(optional &&rhs) && { return hasValue() ? std::move(*this) : std::move(rhs); } #ifndef TL_OPTIONAL_NO_CONSTRR constexpr optional disjunction(optional &&rhs) const && { return hasValue() ? std::move(*this) : std::move(rhs); } #endif /// Takes the value out of the optional, leaving it empty optional take() { optional ret = std::move(*this); reset(); return ret; } using value_type = T &; /// Constructs an optional that does not contain a value. constexpr optional() noexcept : m_value(nullptr) {} constexpr optional(nullopt_t) noexcept : m_value(nullptr) {} /// Copy constructor /// /// If `rhs` contains a value, the stored value is direct-initialized with /// it. Otherwise, the constructed optional is empty. TL_OPTIONAL_11_CONSTEXPR optional(const optional &rhs) noexcept = default; /// Move constructor /// /// If `rhs` contains a value, the stored value is direct-initialized with /// it. Otherwise, the constructed optional is empty. TL_OPTIONAL_11_CONSTEXPR optional(optional &&rhs) = default; /// Constructs the stored value with `u`. template <class U = T, detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value> * = nullptr> constexpr optional(U &&u) : m_value(std::addressof(u)) { static_assert(std::is_lvalue_reference<U>::value, "U must be an lvalue"); } template <class U> constexpr explicit optional(const optional<U> &rhs) : optional(*rhs) {} /// No-op ~optional() = default; /// Assignment to empty. /// /// Destroys the current value if there is one. optional &operator=(nullopt_t) noexcept { m_value = nullptr; return *this; } /// Copy assignment. /// /// Rebinds this optional to the referee of `rhs` if there is one. Otherwise /// resets the stored value in `*this`. optional &operator=(const optional &rhs) = default; /// Rebinds this optional to `u`. template <class U = T, detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value> * = nullptr> optional &operator=(U &&u) { static_assert(std::is_lvalue_reference<U>::value, "U must be an lvalue"); m_value = std::addressof(u); return *this; } /// Converting copy assignment operator. /// /// Rebinds this optional to the referee of `rhs` if there is one. Otherwise /// resets the stored value in `*this`. template <class U> optional &operator=(const optional<U> &rhs) { m_value = std::addressof(rhs.value()); return *this; } /// Constructs the value in-place, destroying the current one if there is /// one. template <class... Args> T &emplace(Args &&...args) noexcept { static_assert(std::is_constructible<T, Args &&...>::value, "T must be constructible with Args"); *this = nullopt; this->construct(std::forward<Args>(args)...); return value(); } void swap(optional &rhs) noexcept { std::swap(m_value, rhs.m_value); } constexpr bool hasValue() const noexcept { return m_value != nullptr; } private: /// Returns a pointer to the stored value constexpr const T *operator->() const { return m_value; } TL_OPTIONAL_11_CONSTEXPR T *operator->() { return m_value; } /// Returns the stored value TL_OPTIONAL_11_CONSTEXPR T &operator*() { return *m_value; } constexpr const T &operator*() const { return *m_value; } constexpr explicit operator bool() const noexcept { return m_value != nullptr; } /// Returns the contained value if there is one, otherwise throws /// bad_optional_access TL_OPTIONAL_11_CONSTEXPR T &value() { if (hasValue()) return *m_value; throw bad_optional_access(); } TL_OPTIONAL_11_CONSTEXPR const T &value() const { if (hasValue()) return *m_value; throw bad_optional_access(); } public: /// Returns the stored value if there is one, otherwise returns `u` template <class U> constexpr T &getOr(U &&u) const & { static_assert(std::is_copy_constructible<T>::value && std::is_convertible<U &&, T>::value, "T must be copy constructible and convertible from U"); return hasValue() ? **this : static_cast<T>(std::forward<U>(u)); } /// \group getOr template <class U> TL_OPTIONAL_11_CONSTEXPR T &getOr(U &&u) && { static_assert(std::is_move_constructible<T>::value && std::is_convertible<U &&, T>::value, "T must be move constructible and convertible from U"); return hasValue() ? **this : static_cast<T>(std::forward<U>(u)); } /// Destroys the stored value if one exists, making the optional empty void reset() noexcept { m_value = nullptr; } private: T *m_value; }; } // namespace tl namespace std { // TODO SFINAE template <class T> struct hash<tl::optional<T>> { ::std::size_t operator()(const tl::optional<T> &o) const { if (!o.hasValue()) return 0; return std::hash<tl::detail::remove_const_t<T>>()(*o); } }; } // namespace std #endif tl::optional<int> maybePlayerAge(const std::string& playerName, const std::map<std::string, int> &ageByName) { const auto search = ageByName.find(playerName); if (search != ageByName.end()) { return search->second; } return tl::nullopt; } auto isOlderThanThirty(const int currentAge) { return currentAge>30; } tl::optional<std::string> maybePlayerName(const int shirtNumber, const std::map<int, std::string> &nameByShirtNo) { const auto search = nameByShirtNo.find(shirtNumber); if (search != nameByShirtNo.end()) { return search->second; } return tl::nullopt; } void printPlayerName(const std::string& playerName) { std::cout << playerName << " was found!"; } void printNoPlayerFound() { std::cout << "No player found"; } int main() { const auto shirtNumber = 8; const auto nameByShirtNo = std::map<int, std::string>{{8, "Andres Iniesta"}}; auto ageByPlayerName = std::map<std::string, int>{{"Andres Iniesta", 31}}; maybePlayerName(shirtNumber, nameByShirtNo) .flatMap([&ageByPlayerName](auto playerName){ return maybePlayerAge(playerName, ageByPlayerName); }) .filter(isOlderThanThirty) .map([](auto){std::cout << "Player with shirt number " << shirtNumber << " is older 30";}) .orElse([]{ std::cout << "Player with shirt number " << shirtNumber << " is either not existing or younger than 31"; }); return 0; }
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