formula_decrement_node.hpp

// Copyright Take Vos 2020.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "formula_unary_operator_node.hpp"
 
namespace hi::inline v1 {
 
struct formula_decrement_node final : formula_unary_operator_node {
    formula_decrement_node(parse_location location, std::unique_ptr<formula_node> rhs) :
        formula_unary_operator_node(std::move(location), std::move(rhs))
    {
    }
 
    datum evaluate(formula_evaluation_context &context) const override
    {
        auto &rhs_ = rhs->evaluate_lvalue(context);
        try {
            return --rhs_;
        } catch (std::exception const &e) {
            throw operation_error(std::format("{}: Can not evaluate decrement.\n{}", location, e.what()));
        }
    }
 
    std::string string() const noexcept override
    {
        return std::format("(-- {})", *rhs);
    }
};
 
} // namespace hi::inline v1