From a80605972682699ee774f45fc78492160e47dd71 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Ho=C5=99e=C5=88ovsk=C3=BD?=
 <martin.horenovsky@gmail.com>
Date: Sun, 10 Dec 2023 16:26:07 +0100
Subject: [PATCH] Fix uniform_floating_point_distribution for unit ranges

---
 .../catch_random_floating_point_helpers.hpp   |  4 ++--
 ...ch_uniform_floating_point_distribution.hpp |  2 +-
 .../RandomNumberGeneration.tests.cpp          | 20 +++++++++++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/catch2/internal/catch_random_floating_point_helpers.hpp b/src/catch2/internal/catch_random_floating_point_helpers.hpp
index d75b42182f..c59c053916 100644
--- a/src/catch2/internal/catch_random_floating_point_helpers.hpp
+++ b/src/catch2/internal/catch_random_floating_point_helpers.hpp
@@ -31,7 +31,7 @@ namespace Catch {
                            "gamma returns the largest ULP magnitude within "
                            "floating point range [a, b]. This only makes sense "
                            "for floating point types" );
-            assert( a < b );
+            assert( a <= b );
 
             const auto gamma_up = Catch::nextafter( a, std::numeric_limits<FloatType>::infinity() ) - a;
             const auto gamma_down = b - Catch::nextafter( b, -std::numeric_limits<FloatType>::infinity() );
@@ -69,7 +69,7 @@ namespace Catch {
         template <typename FloatType>
         DistanceType<FloatType>
         count_equidistant_floats( FloatType a, FloatType b, FloatType distance ) {
-            assert( a < b );
+            assert( a <= b );
             // We get distance as gamma for our uniform float distribution,
             // so this will round perfectly.
             const auto ag = a / distance;
diff --git a/src/catch2/internal/catch_uniform_floating_point_distribution.hpp b/src/catch2/internal/catch_uniform_floating_point_distribution.hpp
index a1cdfe43fc..23d03b43c3 100644
--- a/src/catch2/internal/catch_uniform_floating_point_distribution.hpp
+++ b/src/catch2/internal/catch_uniform_floating_point_distribution.hpp
@@ -97,7 +97,7 @@ class uniform_floating_point_distribution {
         m_max_steps_in_one_go( Detail::calculate_max_steps_in_one_go(m_ulp_magnitude)),
         m_a_has_leq_magnitude(std::fabs(m_a) <= std::fabs(m_b))
     {
-        assert( a < b );
+        assert( a <= b );
     }
 
     template <typename Generator>
diff --git a/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp b/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
index 379f8b2322..03be6c9cad 100644
--- a/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
@@ -8,6 +8,7 @@
 
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/catch_template_test_macros.hpp>
+#include <catch2/internal/catch_floating_point_helpers.hpp>
 #include <catch2/internal/catch_random_integer_helpers.hpp>
 #include <catch2/internal/catch_random_number_generator.hpp>
 #include <catch2/internal/catch_random_seed_generation.hpp>
@@ -568,3 +569,22 @@ TEMPLATE_TEST_CASE( "uniform_floating_point_distribution is reproducible",
 
     REQUIRE_THAT( generated, Catch::Matchers::RangeEquals( uniform_fp_test_params<TestType>::expected ) );
 }
+
+TEMPLATE_TEST_CASE( "uniform_floating_point_distribution can handle unitary ranges",
+                    "[rng][distribution][floating-point][approvals]",
+                    float,
+                    double ) {
+    std::random_device rd;
+    auto seed = rd();
+    CAPTURE( seed );
+    Catch::SimplePcg32 pcg( seed );
+
+    const auto highest = uniform_fp_test_params<TestType>::highest;
+    Catch::uniform_floating_point_distribution<TestType> dist( highest,
+                                                               highest );
+
+    constexpr auto iters = 20;
+    for (int i = 0; i < iters; ++i) {
+        REQUIRE( Catch::Detail::directCompare( dist( pcg ), highest ) );
+    }
+}