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// Copyright (c) 2019 Egor Tensin <Egor.Tensin@gmail.com>
// This file is part of the "math-server" project.
// For details, see https://github.com/egor-tensin/math-server.
// Distributed under the MIT License.
#pragma once
#include "error.hpp"
#include "../lexer/token.hpp"
#include "../lexer/token_type.hpp"
namespace math::server::parser {
class BinaryOp {
public:
using Token = lexer::Token;
using Type = Token::Type;
static bool is(const Token& token) {
switch (token.get_type()) {
case Type::PLUS:
case Type::MINUS:
case Type::ASTERISK:
case Type::SLASH:
return true;
default:
return false;
}
}
static BinaryOp from_token(const Token& token) {
if (!is(token)) {
throw ParserError{"internal: token is not a binary operator"};
}
return BinaryOp{token};
}
static constexpr unsigned min_precedence() { return 0; }
unsigned get_precedence() const {
switch (m_type) {
case Type::PLUS:
case Type::MINUS:
return min_precedence();
case Type::ASTERISK:
case Type::SLASH:
return min_precedence() + 1;
default:
throw ParserError{"internal: undefined operator precedence"};
}
}
double exec(double lhs, double rhs) const {
switch (m_type) {
case Type::PLUS:
return lhs + rhs;
case Type::MINUS:
return lhs - rhs;
case Type::ASTERISK:
return lhs * rhs;
case Type::SLASH:
// Trapping the CPU would be better?
if (rhs == 0.) {
throw ParserError{"division by zero"};
}
return lhs / rhs;
default:
throw ParserError{"internal: unsupported operator"};
}
}
private:
explicit BinaryOp(const Token& token)
: m_type{token.get_type()}
{ }
Type m_type;
};
}
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