comparison: src/generics/oneof.h
src/generics/oneof.h
- changeset 1428
- ece049033adc
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| 1427:b7ba2af33c13 | 1428:ece049033adc |
|---|---|
| 1 #pragma once | |
| 2 #include <array> | |
| 3 | |
| 4 namespace detail | |
| 5 { | |
| 6 template<typename T, typename Vt> | |
| 7 constexpr bool oneOfCompare(const T& value, Vt *first, Vt *last) | |
| 8 { | |
| 9 return (first == last) | |
| 10 ? false | |
| 11 : (*first) == value | |
| 12 ? true | |
| 13 : detail::oneOfCompare(value, first + 1, last); | |
| 14 } | |
| 15 | |
| 16 template<typename Vt, std::size_t N> | |
| 17 struct OneOfClass | |
| 18 { | |
| 19 std::array<Vt, N> parameters; | |
| 20 | |
| 21 template<typename... Ts> | |
| 22 constexpr OneOfClass(Ts&&... parameters) : | |
| 23 parameters {{parameters...}} {} | |
| 24 | |
| 25 template<typename T> | |
| 26 constexpr bool operator==(const T& value) const | |
| 27 { | |
| 28 return detail::oneOfCompare(value, ¶meters[0], ¶meters[N]); | |
| 29 } | |
| 30 | |
| 31 template<typename T> | |
| 32 constexpr bool operator!=(const T& value) const | |
| 33 { | |
| 34 return !(*this == value); | |
| 35 } | |
| 36 | |
| 37 template<typename T> | |
| 38 constexpr friend bool operator==(const T& value, const OneOfClass<Vt, N>& array) | |
| 39 { | |
| 40 return array == value; | |
| 41 } | |
| 42 | |
| 43 template<typename T> | |
| 44 constexpr friend bool operator!=(const T& value, const OneOfClass<Vt, N>& array) | |
| 45 { | |
| 46 return array != value; | |
| 47 } | |
| 48 }; | |
| 49 }; | |
| 50 | |
| 51 /* | |
| 52 * Returns such an object that compares equal to some value if and only if any of the parameters do. | |
| 53 * Example: (x == any(1, 2, 3)) is equivalent to (x == 1 || x == 2 || x == 3) other than the lack of lazy-evaluation | |
| 54 */ | |
| 55 template<typename... Ts> | |
| 56 constexpr auto oneOf(Ts&&... parameters) | |
| 57 { | |
| 58 using Vt = typename std::common_type<Ts...>::type; | |
| 59 return detail::OneOfClass<Vt, sizeof...(Ts)>({parameters...}); | |
| 60 } | |
| 61 | |
| 62 static_assert(oneOf(1,2,3) == 3, "oneOf unit test"); | |
| 63 static_assert(oneOf(1,2,3) != 5, "oneOf unit test"); | |
| 64 static_assert(3 == oneOf(1,2,3), "oneOf unit test"); | |
| 65 static_assert(5 != oneOf(1,2,3), "oneOf unit test"); |
