is_identity.hpp

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// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_VALUE_FUNCTIONS_IS_IDENTITY_H
#define pRC_CORE_VALUE_FUNCTIONS_IS_IDENTITY_H
 
#include <prc/core/basic/functions/identity.hpp>
#include <prc/core/functors/relative_error.hpp>
#include <prc/core/value/functions/relative_error.hpp>
#include <prc/core/value/limits.hpp>
 
namespace pRC
{
    template<class X, class R = RemoveReference<X>, IsValue TT = Value<R>>
        requires IsDefined<Identity<R>> && IsConstructible<Identity<R>> &&
        IsInvocable<RelativeError, decltype(identity<R>()), X>
    static inline constexpr auto isIdentity(X &&a,
        TT const &tolerance = NumericLimits<TT>::tolerance())
    {
        return relativeError(identity<R>(), forward<X>(a)) <= tolerance;
    }
}
#endif // pRC_CORE_VALUE_FUNCTIONS_IS_IDENTITY_H