Introduce random number (Integral and Float) generators

docs/generators.md

@@ -43,6 +43,9 @@ a test case,
   * `RepeatGenerator<T>` -- repeats output from a generator `n` times
   * `MapGenerator<T, U, Func>` -- returns the result of applying `Func`
   on elements from a different generator
+* 2 specific purpose generators
+  * `RandomIntegerGenerator<Integral>` -- generates random Integrals from range
+  * `RandomFloatGenerator<Float>` -- generates random Floats from range
 
 The generators also have associated helper functions that infer their
 type, making their usage much nicer. These are
@@ -54,6 +57,7 @@ type, making their usage much nicer. These are
 * `repeat(repeats, GeneratorWrapper<T>&&)` for `RepeatGenerator<T>`
 * `map(func, GeneratorWrapper<T>&&)` for `MapGenerator<T, T, Func>` (map `T` to `T`)
 * `map<T>(func, GeneratorWrapper<U>&&)` for `MapGenerator<T, U, Func>` (map `U` to `T`)
+* `range(IntegerOrFloat a, IntegerOrFloat b)` for `RandomIntegerGenerator` or `RandomFloatGenerator`
 
 And can be used as shown in the example below to create a generator
 that returns 100 odd random number:
@@ -69,8 +73,6 @@ TEST_CASE("Generating random ints", "[example][generator]") {
 }
 ```
 
-_Note that `random` is currently not a part of the first-party generators_.
-
 
 Apart from registering generators with Catch2, the `GENERATE` macro has
 one more purpose, and that is to provide simple way of generating trivial

include/catch.hpp

@@ -63,6 +63,7 @@
 #include "internal/catch_capture_matchers.h"
 #endif
 #include "internal/catch_generators.hpp"
+#include "internal/catch_generators_specific.hpp"
 
 // These files are included here so the single_include script doesn't put them
 // in the conditionally compiled sections

include/internal/catch_generators_specific.hpp

@@ -0,0 +1,88 @@
+/*
+ *  Created by Martin on 15/6/2018.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+#ifndef TWOBLUECUBES_CATCH_GENERATORS_SPECIFIC_HPP_INCLUDED
+#define TWOBLUECUBES_CATCH_GENERATORS_SPECIFIC_HPP_INCLUDED
+
+#include "catch_context.h"
+#include "catch_generators.hpp"
+#include "catch_interfaces_config.h"
+
+#include <random>
+
+namespace Catch {
+namespace Generators {
+
+template <typename Float>
+class RandomFloatingGenerator final : public IGenerator<Float> {
+    // FIXME: What is the right seed?
+    std::minstd_rand m_rand;
+    std::uniform_real_distribution<Float> m_dist;
+    Float m_current_number;
+public:
+
+    RandomFloatingGenerator(Float a, Float b):
+        m_rand(getCurrentContext().getConfig()->rngSeed()),
+        m_dist(a, b) {
+        static_cast<void>(next());
+    }
+
+    Float const& get() const override {
+        return m_current_number;
+    }
+    bool next() override {
+        m_current_number = m_dist(m_rand);
+        return true;
+    }
+};
+
+template <typename Integer>
+class RandomIntegerGenerator final : public IGenerator<Integer> {
+    std::minstd_rand m_rand;
+    std::uniform_int_distribution<Integer> m_dist;
+    Integer m_current_number;
+public:
+
+    RandomIntegerGenerator(Integer a, Integer b):
+        m_rand(getCurrentContext().getConfig()->rngSeed()),
+        m_dist(a, b) {
+        static_cast<void>(next());
+    }
+
+    Integer const& get() const override {
+        return m_current_number;
+    }
+    bool next() override {
+        m_current_number = m_dist(m_rand);
+        return true;
+    }
+};
+
+// TODO: Ideally this would be also constrained against the various char types,
+//       but I don't expect users to run into that in practice.
+template <typename T>
+typename std::enable_if<std::is_integral<T>::value && !std::is_same<T, bool>::value,
+GeneratorWrapper<T>>::type
+random(T a, T b) {
+    return GeneratorWrapper<T>(
+        pf::make_unique<RandomIntegerGenerator<T>>(a, b)
+    );
+}
+
+template <typename T>
+typename std::enable_if<std::is_floating_point<T>::value,
+GeneratorWrapper<T>>::type
+random(T a, T b) {
+    return GeneratorWrapper<T>(
+        pf::make_unique<RandomFloatingGenerator<T>>(a, b)
+    );
+}
+
+} // namespace Generators
+} // namespace Catch
+
+
+#endif // TWOBLUECUBES_CATCH_GENERATORS_SPECIFIC_HPP_INCLUDED

projects/CMakeLists.txt

@@ -102,6 +102,7 @@ set(INTERNAL_HEADERS
         ${HEADER_DIR}/internal/catch_external_interfaces.h
         ${HEADER_DIR}/internal/catch_fatal_condition.h
         ${HEADER_DIR}/internal/catch_generators.hpp
+        ${HEADER_DIR}/internal/catch_generators_specific.hpp
         ${HEADER_DIR}/internal/catch_impl.hpp
         ${HEADER_DIR}/internal/catch_interfaces_capture.h
         ${HEADER_DIR}/internal/catch_interfaces_config.h

projects/SelfTest/UsageTests/Generators.tests.cpp

@@ -145,3 +145,16 @@ TEST_CASE("Generators -- adapters", "[generators]") {
         REQUIRE(j > 0);
     }
 }
+
+// Note that because of the non-reproducibility of distributions,
+// anything involving the random generators cannot be part of approvals
+TEST_CASE("Random generator", "[generators][.][approvals]") {
+    SECTION("Infer int from integral arguments") {
+        auto val = GENERATE(take(4, random(0, 1)));
+        STATIC_REQUIRE(std::is_same<decltype(val), int>::value);
+    }
+    SECTION("Infer double from double arguments") {
+        auto val = GENERATE(take(4, random(0., 1.)));
+        STATIC_REQUIRE(std::is_same<decltype(val), double>::value);
+    }
+}