TransformedBy.h

/*
  ==============================================================================
    DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 
    Copyright 2023 by sonible GmbH.
 
    This file is part of VCTR - Versatile Container Templates Reconceptualized.
 
    VCTR is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License version 3
    only, as published by the Free Software Foundation.
 
    VCTR is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License version 3 for more details.
 
    You should have received a copy of the GNU Lesser General Public License
    version 3 along with VCTR.  If not, see <https://www.gnu.org/licenses/>.
  ==============================================================================
*/
 
namespace vctr::expressions
{
 
template <size_t extent, class SrcType, std::invocable<ValueType<SrcType>> FunctionType>
requires (! std::is_void_v<std::invoke_result<FunctionType, ValueType<SrcType>>>)
class TransformedBy : public ExpressionTemplateBase
{
public:
    using value_type = std::invoke_result_t<FunctionType, ValueType<SrcType>>;
 
    VCTR_COMMON_UNARY_EXPRESSION_MEMBERS (TransformedBy, src)
 
    void applyRuntimeArgs (const FunctionType& transformationFunction)
    {
        fn = transformationFunction;
    }
 
    VCTR_FORCEDINLINE constexpr value_type operator[] (size_t i) const
    {
        return fn (src[i]);
    }
 
private:
    using FnCopyType = std::conditional_t<std::copyable<FunctionType>, FunctionType, std::function<value_type (ValueType<SrcType>)>>;
    FnCopyType fn;
};
 
} // namespace vctr::expressions
 
namespace vctr
{
template <class Fn>
constexpr auto transformedBy (Fn&& fn)
{
    return makeTemplateExpressionChainBuilderWithRuntimeArgs<expressions::TransformedBy, std::remove_cvref_t<Fn>> (std::forward<Fn> (fn));
}
 
} // namespace vctr