// 310-Gen-VariablesInGenerator.cpp
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// Shows how to use variables when creating generators.
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// Note that using variables inside generators is dangerous and should
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// be done only if you know what you are doing, because the generators
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// _WILL_ outlive the variables -- thus they should be either captured
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// by value directly, or copied by the generators during construction.
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#include <catch2/catch.hpp>
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#include <random>
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// Lets start by implementing a parametrizable double generator
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class RandomDoubleGenerator : public Catch::Generators::IGenerator<double> {
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std::minstd_rand m_rand;
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std::uniform_real_distribution<> m_dist;
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double current_number;
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public:
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RandomDoubleGenerator(double low, double high):
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m_rand(std::random_device{}()),
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m_dist(low, high)
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{
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static_cast<void>(next());
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}
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double const& get() const override;
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bool next() override {
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current_number = m_dist(m_rand);
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return true;
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}
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};
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// Avoids -Wweak-vtables
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double const& RandomDoubleGenerator::get() const {
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return current_number;
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}
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// Also provide a nice shortcut for creating the generator
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Catch::Generators::GeneratorWrapper<double> random(double low, double high) {
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return Catch::Generators::GeneratorWrapper<double>(std::unique_ptr<Catch::Generators::IGenerator<double>>(new RandomDoubleGenerator(low, high)));
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}
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TEST_CASE("Generate random doubles across different ranges",
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"[generator][example][advanced]") {
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// Workaround for old libstdc++
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using record = std::tuple<double, double>;
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// Set up 3 ranges to generate numbers from
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auto r = GENERATE(table<double, double>({
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record{3, 4},
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record{-4, -3},
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record{10, 1000}
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}));
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// This will not compile (intentionally), because it accesses a variable
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// auto number = GENERATE(take(50, random(r.first, r.second)));
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// We have to manually register the generators instead
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// Notice that we are using value capture in the lambda, to avoid lifetime issues
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auto number = Catch::Generators::generate( CATCH_INTERNAL_LINEINFO,
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[=]{
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using namespace Catch::Generators;
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return makeGenerators(take(50, random(std::get<0>(r), std::get<1>(r))));
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}
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);
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REQUIRE(std::abs(number) > 0);
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}
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// Compiling and running this file will result in 150 successful assertions
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