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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>
#include <cmath>
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:
case Type::CARET:
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; }
static unsigned get_precedence(Type type) {
switch (type) {
case Type::PLUS:
case Type::MINUS:
return min_precedence();
case Type::ASTERISK:
case Type::SLASH:
return min_precedence() + 1;
case Type::CARET:
return min_precedence() + 3;
default:
throw ParserError{"internal: undefined operator precedence"};
}
}
unsigned get_precedence() const { return get_precedence(m_type); }
bool is_right_associative() const {
switch (m_type) {
case Type::CARET:
return true;
default:
return false;
}
}
bool is_left_associative() const { return !is_right_associative(); }
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;
case Type::CARET:
return std::pow(lhs, rhs);
default:
throw ParserError{"internal: unsupported operator"};
}
}
private:
explicit BinaryOp(const Token& token) : m_type{token.get_type()} {}
Type m_type;
};
} // namespace math::server::parser
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