Clean up pairwise_all() and strictly_increasing()

src/core/include/units/magnitude.h

@@ -176,23 +176,31 @@ constexpr auto pi_to_the() { return magnitude<pi_power<Power>()>{}; }
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 // Magnitude concept implementation.
 
-template<typename Predicate, typename... Ts>
+template<typename Predicate>
-constexpr bool pairwise_all(const std::tuple<Ts...> &ts, const Predicate &pred) {
+struct pairwise_all {
+  Predicate predicate;
+
+  template<typename... Ts>
+  constexpr bool operator()(Ts&&... ts) const {
     // 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, &pred]<std::size_t... Is>(std::integer_sequence<std::size_t, Is...>) {
+    return [this]<std::size_t... Is>(std::tuple<Ts...> &&t, std::index_sequence<Is...>) {
-    return (pred(std::get<Is>(ts), std::get<Is + 1>(ts)) && ...);
+      return (predicate(std::get<Is>(t), std::get<Is + 1>(t)) && ...);
-  }(std::make_index_sequence<num_comparisons>());
+    }(std::make_tuple(std::forward<Ts>(ts)...), std::make_index_sequence<num_comparisons>());
   }
+};
+
+template<typename T>
+pairwise_all(T) -> pairwise_all<T>;
 
 // Check whether a tuple of (possibly heterogeneously typed) values are strictly increasing.
 template<typename... Ts>
-constexpr bool strictly_increasing(const std::tuple<Ts...> &ts) {
+constexpr bool strictly_increasing(Ts&&... ts) {
-  return pairwise_all(ts, std::less{});
+  return pairwise_all{std::less{}}(std::forward<Ts>(ts)...);
 }
 
 namespace detail

test/unit_test/runtime/magnitude_test.cpp

@@ -30,23 +30,23 @@ namespace units::mag
 
 TEST_CASE("strictly_increasing")
 {
-  SECTION ("Empty tuple is sorted")
+  SECTION ("Empty input is sorted")
   {
-    CHECK(strictly_increasing(std::make_tuple()));
+    CHECK(strictly_increasing());
   }
 
-  SECTION ("Single-element tuple is sorted")
+  SECTION ("Single-element input is sorted")
   {
-    CHECK(strictly_increasing(std::make_tuple(3)));
+    CHECK(strictly_increasing(3));
-    CHECK(strictly_increasing(std::make_tuple(15.42)));
+    CHECK(strictly_increasing(15.42));
-    CHECK(strictly_increasing(std::make_tuple('c')));
+    CHECK(strictly_increasing('c'));
   }
 
-  SECTION ("Multi-element tuples compare correctly")
+  SECTION ("Multi-value inputs compare correctly")
   {
-    CHECK(strictly_increasing(std::make_tuple(3, 3.14)));
+    CHECK(strictly_increasing(3, 3.14));
-    CHECK(!strictly_increasing(std::make_tuple(3, 3.0)));
+    CHECK(!strictly_increasing(3, 3.0));
-    CHECK(!strictly_increasing(std::make_tuple(4, 3.0)));
+    CHECK(!strictly_increasing(4, 3.0));
   }
 }
 
@@ -94,9 +94,6 @@ TEST_CASE("strictly_increasing")
 //   }
 // }
 
-template<double x>
-using double_v = 2 * x;
-
 TEST_CASE("Multiplication works for magnitudes")
 {
   SECTION("Reciprocals reduce to null magnitude")
@@ -107,7 +104,6 @@ TEST_CASE("Multiplication works for magnitudes")
   SECTION("Products work as expected")
   {
     CHECK(make_ratio<4, 5>() * make_ratio<4, 3>() == make_ratio<16, 15>());
-    CHECK(double_v<1.5> == 3.0);
   }
 
   //SECTION("Products handle pi correctly")
@@ -205,23 +201,23 @@ TEST_CASE("pairwise_all evaluates all pairs")
 {
   SECTION("always true for empty tuples")
   {
-    CHECK(pairwise_all(std::make_tuple(), [](auto, auto){ return true; }));
+    CHECK(pairwise_all{[](auto, auto){ return true; }}());
-    CHECK(pairwise_all(std::make_tuple(), [](auto, auto){ return false; }));
+    CHECK(pairwise_all{[](auto, auto){ return false; }}());
   }
 
   SECTION("always true for single-element tuples")
   {
-    CHECK(pairwise_all(std::make_tuple(1), [](auto, auto){ return true; }));
+    CHECK(pairwise_all{[](auto, auto){ return true; }}(1));
-    CHECK(pairwise_all(std::make_tuple(3.14), [](auto, auto){ return false; }));
+    CHECK(pairwise_all{[](auto, auto){ return false; }}(3.14));
-    CHECK(pairwise_all(std::make_tuple('x'), [](auto, auto){ return true; }));
+    CHECK(pairwise_all{[](auto, auto){ return true; }}('x'));
   }
 
   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::less{}}(1, 1.5));
-    CHECK(pairwise_all(std::make_tuple(1, 1.5, 2), std::less{}));
+    CHECK(pairwise_all{std::less{}}(1, 1.5, 2));
-    CHECK(!pairwise_all(std::make_tuple(1, 2.0, 2), std::less{}));
+    CHECK(!pairwise_all{std::less{}}(1, 2.0, 2));
-    CHECK(!pairwise_all(std::make_tuple(1, 2.5, 2), std::less{}));
+    CHECK(!pairwise_all{std::less{}}(1, 2.5, 2));
   }
 }