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comparison gcc/testsuite/g++.dg/cpp2a/concepts-pr67860.C @ 145:1830386684a0

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gcc-9.2.0
author anatofuz
date Thu, 13 Feb 2020 11:34:05 +0900
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131:84e7813d76e9 145:1830386684a0
1 // { dg-do compile { target c++2a } }
2 // { dg-additional-options "-fconcepts-ts" }
3
4 #include <type_traits>
5
6 inline constexpr bool and_impl() { return true; }
7
8 template <class OperandFirst, class... OperandsRest>
9 constexpr bool and_impl(OperandFirst operand_first,
10 OperandsRest... operands_rest) {
11 return operand_first && and_impl(operands_rest...);
12 }
13
14 template <class... Operands> constexpr bool and_(Operands... operands) {
15 return and_impl(operands...);
16 }
17
18 template <class X> concept bool C() { return true; }
19
20 // v1
21 template<int, class... Xs>
22 requires and_(C<Xs>()...)
23 constexpr int f(const Xs&... xs) {
24 return 0;
25 }
26
27 // v2
28 template<int, class... Xs>
29 constexpr int f(const Xs&... xs) {
30 return 1;
31 }
32
33 int main() {
34 static_assert(f<10>(3.0, 2.0f) == 0);
35 return 0;
36 }
37
38 // 2nd example
39
40 template <typename T, typename... Us>
41 concept bool AreType() {
42 return (std::is_same<T,Us>::value && ...);
43 // return true; gives the same overloaded error
44 }
45
46 // Function with constraint
47 template<typename T, AreType<T>... Us>
48 constexpr bool isValid(Us... us) {
49 return true;
50 }
51
52 // Function with no constraint
53 template<typename T, typename... U>
54 constexpr bool isValid(U... u) {
55 return false;
56 }
57
58 int main2() {
59 static_assert(isValid<int>(1)); // also isValid<int>(1, 2, 3); etc
60 return 0;
61 }