git clone https://github.com/changkun/modern-cpp-tutorial.git
coliru.stacked-crooked.com
外部模板
#include
#include
template class std::vector; // forcely instantiation
extern template class std::vector; // external template for avoiding instantiation in this file
template class MagicType {
bool magic = T;
};
int main() {
// the >> in template
std::vector> matrix;
std::vector2)>> magic; // legal, but not recommended
} g++ -std=c++17 2.12.external.template.cpp -o exttemp
注意：
尖括号 “>”
std::vector> matrix; 不加-std=c++17，按传统c++模式，比如error：
编译器会给出提示的：
2.12.external.template.cpp:17:18: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11
类型别名模板
#include
#include
#include
template
class MagicType {
public:
T dark;
U magic;
};
// illegal
// template
// typedef MagicType, std::string> FakeDarkMagic;
typedef int (*process)(void *);
using NewProcess = int(*)(void *);
template
using TrueDarkMagic = MagicType, std::string>;
int main() {
// FakeDarkMagic me;
TrueDarkMagic you;
} g++ -std=c++17 2.13.alias.template.cpp -o altemp
模板求和：
#include
template
auto add(T x, U y) -> decltype(x+y) {
return x+y;
}
int main() {
std::cout << add(1, 2) << std::endl;
} g++ -std=c++17 2.14.default.template.param.cpp -o detemp
变长参数模板
#include
#include
#include
// sizeof...
template
void magic(Ts... args) {
std::cout << sizeof...(args) << std::endl;
}
// 1. recursive parameter unpack
template
void printf1(T0 value) {
std::cout << value << std::endl;
}
template
void printf1(T value, Ts... args) {
std::cout << value << std::endl;
printf1(args...);
}
// 2. variadic template parameter unfold
template
void printf2(T0 t0, T... t) {
std::cout << t0 << std::endl;
if constexpr (sizeof...(t) > 0) printf2(t...);
}
// 3. parameter unpack using initializer_list
template
auto printf3(T value, Ts... args) {
std::cout << value << std::endl;
(void) std::initializer_list{([&args] {
std::cout << args << std::endl;
}(), value)...};
}
int main() {
magic();
magic(1);
magic(1,"");
printf1(1, 2, "123", 1.1);
printf2(1, 2.3, "abc");
printf3(111, 123, "alpha", 1.2);
return 0;
} 折叠表达式
#include
template
auto sum(T ... t) {
return (t + ...);
}
int main() {
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
} 非类型模板参数推导
#include
template void foo() {
std::cout << value << std::endl;
return;
}
int main() {
foo<10>(); // value is deduced as type int
}
shiyanlou:2/ (master) $ g++ -std=c++17 2.12.external.template.cpp -o exttemp
shiyanlou:2/ (master*) $ ./exttemp [14:39:12]
shiyanlou:2/ (master*) $ g++ 2.12.external.template.cpp -o exttemp [14:39:16]
2.12.external.template.cpp:17:18: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11
bool magic = T;
^
2.12.external.template.cpp: In function \u2018int main()\u2019:
2.12.external.template.cpp:22:32: error: \u2018>>\u2019 should be \u2018> >\u2019 within a nested template argument list
std::vector> matrix;
^
2.12.external.template.cpp:23:35: error: \u2018magic\u2019 was not declared in this scope
std::vector2)>> magic; // legal, but not recommended
^
2.12.external.template.cpp:23:35: error: template argument 1 is invalid
2.12.external.template.cpp:23:17: error: template argument 1 is invalid
std::vector2)>> magic; // legal, but not recommended
^
2.12.external.template.cpp:23:17: error: template argument 2 is invalid
shiyanlou:2/ (master*) $ g++ -std=c++17 2.13.alias.template.cpp -o altemp
shiyanlou:2/ (master*) $ ./altemp [14:46:30]
shiyanlou:2/ (master*) $ g++ -std=c++17 2.14.default.template.param.cpp -o detemp
shiyanlou:2/ (master*) $ ./detemp [14:51:33]
3
shiyanlou:2/ (master*) $ g++ -std=c++17 2.15.variadic.template.param.cpp -o vartemp
2.15.variadic.template.param.cpp: In function \u2018void printf2(T0, T ...)\u2019:
2.15.variadic.template.param.cpp:36:8: error: expected \u2018(\u2019 before \u2018constexpr\u2019
if constexpr (sizeof...(t) > 0) printf2(t...);
^
2.15.variadic.template.param.cpp: In function \u2018auto printf3(T, Ts ...)\u2019:
2.15.variadic.template.param.cpp:43:40: error: parameter packs not expanded with \u2018...\u2019:
(void) std::initializer_list{([&args] {
^
2.15.variadic.template.param.cpp:43:40: note: \u2018args\u2019
2.15.variadic.template.param.cpp:43:44: error: parameter packs not expanded with \u2018...\u2019:
(void) std::initializer_list{([&args] {
^
2.15.variadic.template.param.cpp:43:44: note: \u2018args\u2019
2.15.variadic.template.param.cpp:45:16: error: expansion pattern \u2018((), value)\u2019 contains no argument packs
}(), value)...};
^
2.15.variadic.template.param.cpp: In instantiation of \u2018auto printf3(T, Ts ...) [with T = int; Ts = {int, const char*, double}]\u2019:
2.15.variadic.template.param.cpp:55:35: required from here
2.15.variadic.template.param.cpp:43:5: error: no matching function for call to \u2018std::initializer_list::initializer_list()\u2019
(void) std::initializer_list{([&args] {
^
In file included from /usr/include/c++/5/bits/range_access.h:36:0,
from /usr/include/c++/5/string:51,
from /usr/include/c++/5/bits/locale_classes.h:40,
from /usr/include/c++/5/bits/ios_base.h:41,
from /usr/include/c++/5/ios:42,
from /usr/include/c++/5/ostream:38,
from /usr/include/c++/5/iostream:39,
from 2.15.variadic.template.param.cpp:10:
/usr/include/c++/5/initializer_list:66:17: note: candidate: constexpr std::initializer_list<_E>::initializer_list() [with _E = int]
constexpr initializer_list() noexcept
^
/usr/include/c++/5/initializer_list:66:17: note: candidate expects 0 arguments, 1 provided
/usr/include/c++/5/initializer_list:62:17: note: candidate: constexpr std::initializer_list<_E>::initializer_list(std::initializer_list<_E>::const_iterator, std::initializer_list<_E>::size_type) [with _E = int; std::initializer_list<_E>::const_iterator = const int*; std::initializer_list<_E>::size_type = long unsigned int]
constexpr initializer_list(const_iterator __a, size_type __l)
^
/usr/include/c++/5/initializer_list:62:17: note: candidate expects 2 arguments, 1 provided
/usr/include/c++/5/initializer_list:47:11: note: candidate: constexpr std::initializer_list::initializer_list(const std::initializer_list&)
class initializer_list
^
/usr/include/c++/5/initializer_list:47:11: note: conversion of argument 1 would be ill-formed:
/usr/include/c++/5/initializer_list:47:11: note: candidate: constexpr std::initializer_list::initializer_list(std::initializer_list&&)
/usr/include/c++/5/initializer_list:47:11: note: conversion of argument 1 would be ill-formed:
shiyanlou:2/ (master*) $ ./2.15.variadic.template.param.cpp [14:56:06]
shiyanlou:2/ (master*) $ g++ -std=c++17 2.15.variadic.template.param.cpp -o vartemp
2.15.variadic.template.param.cpp: In function \u2018void printf2(T0, T ...)\u2019:
2.15.variadic.template.param.cpp:36:8: error: expected \u2018(\u2019 before \u2018constexpr\u2019
if constexpr (sizeof...(t) > 0) printf2(t...);
^
2.15.variadic.template.param.cpp: In function \u2018auto printf3(T, Ts ...)\u2019:
2.15.variadic.template.param.cpp:43:40: error: parameter packs not expanded with \u2018...\u2019:
(void) std::initializer_list{([&args] {
^
2.15.variadic.template.param.cpp:43:40: note: \u2018args\u2019
2.15.variadic.template.param.cpp:43:44: error: parameter packs not expanded with \u2018...\u2019:
(void) std::initializer_list{([&args] {
^
2.15.variadic.template.param.cpp:43:44: note: \u2018args\u2019
2.15.variadic.template.param.cpp:45:16: error: expansion pattern \u2018((), value)\u2019 contains no argument packs
}(), value)...};
^
2.15.variadic.template.param.cpp: In instantiation of \u2018auto printf3(T, Ts ...) [with T = int; Ts = {int, const char*, double}]\u2019:
2.15.variadic.template.param.cpp:55:35: required from here
2.15.variadic.template.param.cpp:43:5: error: no matching function for call to \u2018std::initializer_list::initializer_list()\u2019
(void) std::initializer_list{([&args] {
^
In file included from /usr/include/c++/5/bits/range_access.h:36:0,
from /usr/include/c++/5/string:51,
from /usr/include/c++/5/bits/locale_classes.h:40,
from /usr/include/c++/5/bits/ios_base.h:41,
from /usr/include/c++/5/ios:42,
from /usr/include/c++/5/ostream:38,
from /usr/include/c++/5/iostream:39,
from 2.15.variadic.template.param.cpp:10:
/usr/include/c++/5/initializer_list:66:17: note: candidate: constexpr std::initializer_list<_E>::initializer_list() [with _E = int]
constexpr initializer_list() noexcept
^
/usr/include/c++/5/initializer_list:66:17: note: candidate expects 0 arguments, 1 provided
/usr/include/c++/5/initializer_list:62:17: note: candidate: constexpr std::initializer_list<_E>::initializer_list(std::initializer_list<_E>::const_iterator, std::initializer_list<_E>::size_type) [with _E = int; std::initializer_list<_E>::const_iterator = const int*; std::initializer_list<_E>::size_type = long unsigned int]
constexpr initializer_list(const_iterator __a, size_type __l)
^
/usr/include/c++/5/initializer_list:62:17: note: candidate expects 2 arguments, 1 provided
/usr/include/c++/5/initializer_list:47:11: note: candidate: constexpr std::initializer_list::initializer_list(const std::initializer_list&)
class initializer_list
^
/usr/include/c++/5/initializer_list:47:11: note: conversion of argument 1 would be ill-formed:
/usr/include/c++/5/initializer_list:47:11: note: candidate: constexpr std::initializer_list::initializer_list(std::initializer_list&&)
/usr/include/c++/5/initializer_list:47:11: note: conversion of argument 1 would be ill-formed:
shiyanlou:2/ (master*) $ g++ -std=c++17 2.16.fold.expression.cpp -o foexp [14:56:27]
2.16.fold.expression.cpp: In function \u2018auto sum(T ...)\u2019:
2.16.fold.expression.cpp:13:17: error: expected primary-expression before \u2018...\u2019 token
return (t + ...);
^
2.16.fold.expression.cpp:13:17: error: expected \u2018)\u2019 before \u2018...\u2019 token
2.16.fold.expression.cpp:13:20: error: parameter packs not expanded with \u2018...\u2019:
return (t + ...);
^
2.16.fold.expression.cpp:13:20: note: \u2018t\u2019
2.16.fold.expression.cpp: In function \u2018int main()\u2019:
2.16.fold.expression.cpp:16:15: error: no match for \u2018operator<<\u2019 (operand types are \u2018std::ostream {aka std::basic_ostream}\u2019 and \u2018void\u2019)
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:108:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ostream_type& (*)(std::basic_ostream<_CharT, _Traits>::__ostream_type&)) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(__ostream_type& (*__pf)(__ostream_type&))
^
/usr/include/c++/5/ostream:108:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018std::basic_ostream::__ostream_type& (*)(std::basic_ostream::__ostream_type&) {aka std::basic_ostream& (*)(std::basic_ostream&)}\u2019
/usr/include/c++/5/ostream:117:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ios_type& (*)(std::basic_ostream<_CharT, _Traits>::__ios_type&)) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream; std::basic_ostream<_CharT, _Traits>::__ios_type = std::basic_ios]
operator<<(__ios_type& (*__pf)(__ios_type&))
^
/usr/include/c++/5/ostream:117:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018std::basic_ostream::__ios_type& (*)(std::basic_ostream::__ios_type&) {aka std::basic_ios& (*)(std::basic_ios&)}\u2019
/usr/include/c++/5/ostream:127:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(ios_base& (*__pf) (ios_base&))
^
/usr/include/c++/5/ostream:127:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018std::ios_base& (*)(std::ios_base&)\u2019
/usr/include/c++/5/ostream:166:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(long __n)
^
/usr/include/c++/5/ostream:166:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018long int\u2019
/usr/include/c++/5/ostream:170:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(unsigned long __n)
^
/usr/include/c++/5/ostream:170:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018long unsigned int\u2019
/usr/include/c++/5/ostream:174:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(bool __n)
^
/usr/include/c++/5/ostream:174:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018bool\u2019
In file included from /usr/include/c++/5/ostream:638:0,
from /usr/include/c++/5/iostream:39,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/bits/ostream.tcc:91:5: note: candidate: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char; _Traits = std::char_traits]
basic_ostream<_CharT, _Traits>::
^
/usr/include/c++/5/bits/ostream.tcc:91:5: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018short int\u2019
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:181:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(unsigned short __n)
^
/usr/include/c++/5/ostream:181:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018short unsigned int\u2019
In file included from /usr/include/c++/5/ostream:638:0,
from /usr/include/c++/5/iostream:39,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/bits/ostream.tcc:105:5: note: candidate: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char; _Traits = std::char_traits]
basic_ostream<_CharT, _Traits>::
^
/usr/include/c++/5/bits/ostream.tcc:105:5: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018int\u2019
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:192:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(unsigned int __n)
^
/usr/include/c++/5/ostream:192:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018unsigned int\u2019
/usr/include/c++/5/ostream:201:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(long long __n)
^
/usr/include/c++/5/ostream:201:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018long long int\u2019
/usr/include/c++/5/ostream:205:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(unsigned long long __n)
^
/usr/include/c++/5/ostream:205:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018long long unsigned int\u2019
/usr/include/c++/5/ostream:220:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(double __f)
^
/usr/include/c++/5/ostream:220:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018double\u2019
/usr/include/c++/5/ostream:224:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(float __f)
^
/usr/include/c++/5/ostream:224:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018float\u2019
/usr/include/c++/5/ostream:232:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(long double __f)
^
/usr/include/c++/5/ostream:232:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018long double\u2019
/usr/include/c++/5/ostream:245:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream]
operator<<(const void* __p)
^
/usr/include/c++/5/ostream:245:7: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018const void*\u2019
In file included from /usr/include/c++/5/ostream:638:0,
from /usr/include/c++/5/iostream:39,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/bits/ostream.tcc:119:5: note: candidate: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char; _Traits = std::char_traits; std::basic_ostream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf]
basic_ostream<_CharT, _Traits>::
^
/usr/include/c++/5/bits/ostream.tcc:119:5: note: no known conversion for argument 1 from \u2018void\u2019 to \u2018std::basic_ostream::__streambuf_type* {aka std::basic_streambuf*}\u2019
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:628:5: note: candidate: template std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&)
operator<<(basic_ostream<_CharT, _Traits>&& __os, const _Tp& __x)
^
/usr/include/c++/5/ostream:628:5: note: template argument deduction/substitution failed:
/usr/include/c++/5/ostream: In substitution of \u2018template std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT = char; _Traits = std::char_traits; _Tp = void]\u2019:
2.16.fold.expression.cpp:16:51: required from here
/usr/include/c++/5/ostream:628:5: error: forming reference to void
/usr/include/c++/5/ostream:574:5: note: candidate: template std::basic_ostream& std::operator<<(std::basic_ostream&, const unsigned char*)
operator<<(basic_ostream& __out, const unsigned char* __s)
^
/usr/include/c++/5/ostream:574:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018const unsigned char*\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:569:5: note: candidate: template std::basic_ostream& std::operator<<(std::basic_ostream&, const signed char*)
operator<<(basic_ostream& __out, const signed char* __s)
^
/usr/include/c++/5/ostream:569:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018const signed char*\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:556:5: note: candidate: template std::basic_ostream& std::operator<<(std::basic_ostream&, const char*)
operator<<(basic_ostream& __out, const char* __s)
^
/usr/include/c++/5/ostream:556:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018const char*\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/ostream:638:0,
from /usr/include/c++/5/iostream:39,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/bits/ostream.tcc:321:5: note: candidate: template std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const char*)
operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s)
^
/usr/include/c++/5/bits/ostream.tcc:321:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018const char*\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:539:5: note: candidate: template std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const _CharT*)
operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
^
/usr/include/c++/5/ostream:539:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:51: note: mismatched types \u2018const _CharT*\u2019 and \u2018void\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:519:5: note: candidate: template std::basic_ostream& std::operator<<(std::basic_ostream&, unsigned char)
operator<<(basic_ostream& __out, unsigned char __c)
^
/usr/include/c++/5/ostream:519:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018unsigned char\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:514:5: note: candidate: template std::basic_ostream& std::operator<<(std::basic_ostream&, signed char)
operator<<(basic_ostream& __out, signed char __c)
^
/usr/include/c++/5/ostream:514:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018signed char\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:508:5: note: candidate: template std::basic_ostream& std::operator<<(std::basic_ostream&, char)
operator<<(basic_ostream& __out, char __c)
^
/usr/include/c++/5/ostream:508:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018char\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:502:5: note: candidate: template std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char)
operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
^
/usr/include/c++/5/ostream:502:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018char\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/iostream:39:0,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/ostream:497:5: note: candidate: template std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, _CharT)
operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
^
/usr/include/c++/5/ostream:497:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:51: note: deduced conflicting types for parameter \u2018_CharT\u2019 (\u2018char\u2019 and \u2018void\u2019)
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/bits/ios_base.h:46:0,
from /usr/include/c++/5/ios:42,
from /usr/include/c++/5/ostream:38,
from /usr/include/c++/5/iostream:39,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/system_error:209:5: note: candidate: template std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::error_code&)
operator<<(basic_ostream<_CharT, _Traits>& __os, const error_code& __e)
^
/usr/include/c++/5/system_error:209:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:21: note: cannot convert \u2018sum<{int, int, int, int, int, int, int, int, int, int}>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)\u2019 (type \u2018void\u2019) to type \u2018const std::error_code&\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
In file included from /usr/include/c++/5/string:52:0,
from /usr/include/c++/5/bits/locale_classes.h:40,
from /usr/include/c++/5/bits/ios_base.h:41,
from /usr/include/c++/5/ios:42,
from /usr/include/c++/5/ostream:38,
from /usr/include/c++/5/iostream:39,
from 2.16.fold.expression.cpp:10:
/usr/include/c++/5/bits/basic_string.h:5172:5: note: candidate: template std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)
operator<<(basic_ostream<_CharT, _Traits>& __os,
^
/usr/include/c++/5/bits/basic_string.h:5172:5: note: template argument deduction/substitution failed:
2.16.fold.expression.cpp:16:51: note: mismatched types \u2018const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>\u2019 and \u2018void\u2019
std::cout << sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) << std::endl;
^
shiyanlou:2/ (master*) $ g++ -std=c++17 2.18.non.type.template.auto.cpp -o notemp
2.18.non.type.template.auto.cpp:12:16: error: \u2018auto\u2019 parameter not permitted in this context
template void foo() {
^
2.18.non.type.template.auto.cpp: In function \u2018int main()\u2019:
2.18.non.type.template.auto.cpp:18:13: error: no matching function for call to \u2018foo()\u2019
foo<10>(); // value is deduced as type int
^
2.18.non.type.template.auto.cpp:12:28: note: candidate: template<value> void foo()
template void foo() {
^
2.18.non.type.template.auto.cpp:12:28: note: template argument deduction/substitution failed:
2.18.non.type.template.auto.cpp:18:13: note: invalid template non-type parameter
foo<10>(); // value is deduced as type int
^
shiyanlou:2/ (master*) $ [15:03:09]
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