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meta.hpp/develop/manuals/meta_examples/variable_example.cpp
BlackMATov eb8857d56d Happy New Year! 🥳
2025-01-17 19:33:53 +07:00

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/*******************************************************************************
* This file is part of the "https://github.com/blackmatov/meta.hpp"
* For conditions of distribution and use, see copyright notice in LICENSE.md
* Copyright (C) 2021-2025, by Matvey Cherevko (blackmatov@gmail.com)
******************************************************************************/
#include <meta.hpp/meta_all.hpp>
#include <doctest/doctest.h>
#include <fmt/core.h>
namespace
{
const double pi_v{3.1415926536};
const double sqrt2_v{1.4142135624};
}
TEST_CASE("meta/meta_examples/variable/usage") {
namespace meta = meta_hpp;
// 'constants' local scope declaration
const meta::scope constants_scope = meta::local_scope_("constants")
.variable_("pi_v", &pi_v)
.variable_("sqrt2_v", &sqrt2_v);
// finds the variable by name 'pi_v'
const meta::variable pi_variable = constants_scope.get_variable("pi_v");
// checks the type and data type of the found variable
CHECK(pi_variable.get_type() == meta::resolve_type<const double*>());
CHECK(pi_variable.get_type().get_data_type() == meta::resolve_type<double>());
// retrieves a variable value
const meta::uvalue pi_variable_value = pi_variable.get();
// checks the type of the retrieved value
CHECK(pi_variable_value.get_type() == meta::resolve_type<double>());
// checks the typed variable value
CHECK(pi_variable_value.as<double>() == doctest::Approx(3.14).epsilon(0.01));
// we can change variable values, but only non-const
CHECK_FALSE(pi_variable.try_set(6.0));
// prints all variables in the scope
fmt::print("* {}\n", constants_scope.get_name());
for ( const meta::variable& variable : constants_scope.get_variables() ) {
fmt::print(" - {} : {}\n",
variable.get_name(),
variable.get().as<double>());
}
// Output:
// * constants
// - pi_v : 3.1415926536
// - sqrt2_v : 1.4142135624
}