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Factor out logic into pairwise_all() helper

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We could move this somewhere more generic if we want.
This commit is contained in:
Chip Hogg
2022-01-03 15:20:05 -05:00
parent cef01ba67c
commit bb4fe5040d
2 changed files with 34 additions and 5 deletions
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15
src/core/include/units/magnitude.h
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@@ -186,20 +186,25 @@ struct is_base_power<base_power<B, E>>
template<typename T>
struct is_magnitude: std::false_type {};
// Check whether a tuple of (possibly heterogeneously typed) values are strictly increasing.
template<typename... Ts>
constexpr bool strictly_increasing(const std::tuple<Ts...> &ts) {
template<typename Predicate, typename... Ts>
constexpr bool pairwise_all(const std::tuple<Ts...> &ts, const Predicate &pred) {
// Carefully handle different sizes, avoiding unsigned integer underflow.
constexpr auto num_comparisons = [](auto num_elements) {
return (num_elements > 1) ? (num_elements - 1) : 0;
}(sizeof...(Ts));
// Compare zero or more pairs of neighbours as needed.
return [&ts]<std::size_t... Is>(std::integer_sequence<std::size_t, Is...>) {
return ((std::get<Is>(ts) < std::get<Is + 1>(ts)) && ...);
return [&ts, &pred]<std::size_t... Is>(std::integer_sequence<std::size_t, Is...>) {
return (pred(std::get<Is>(ts), std::get<Is + 1>(ts)) && ...);
}(std::make_index_sequence<num_comparisons>());
}
// Check whether a tuple of (possibly heterogeneously typed) values are strictly increasing.
template<typename... Ts>
constexpr bool strictly_increasing(const std::tuple<Ts...> &ts) {
return pairwise_all(ts, std::less{});
}
// To be a valid magnitude, one must be a magnitude<...> of BasePowers with nonzero exponents, sorted by increasing base
// value.
template<BasePower... Bs>

24
test/unit_test/runtime/magnitude_test.cpp
View File

@@ -374,6 +374,30 @@ TEST_CASE("is_prime detects primes")
}
}
TEST_CASE("pairwise_all evaluates all pairs")
{
SECTION("always true for empty tuples")
{
CHECK(pairwise_all(std::make_tuple(), [](auto a, auto b){ return true; }));
CHECK(pairwise_all(std::make_tuple(), [](auto a, auto b){ return false; }));
}
SECTION("always true for single-element tuples")
{
CHECK(pairwise_all(std::make_tuple(1), [](auto a, auto b){ return true; }));
CHECK(pairwise_all(std::make_tuple(3.14), [](auto a, auto b){ return false; }));
CHECK(pairwise_all(std::make_tuple('x'), [](auto a, auto b){ return true; }));
}
SECTION("true for longer tuples iff true for all neighbouring pairs")
{
CHECK(pairwise_all(std::make_tuple(1, 1.5), std::less{}));
CHECK(pairwise_all(std::make_tuple(1, 1.5, 2), std::less{}));
CHECK(!pairwise_all(std::make_tuple(1, 2.0, 2), std::less{}));
CHECK(!pairwise_all(std::make_tuple(1, 2.5, 2), std::less{}));
}
}
} // namespace detail
} // namespace units::mag