mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-10-02 22:02:51 +01:00
92 lines
2.8 KiB
C++
92 lines
2.8 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
|
|
// Exceptions. See /LICENSE for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
|
|
#ifndef PARSER_PRECEDENCE_H_
|
|
#define PARSER_PRECEDENCE_H_
|
|
|
|
#include "lexer/token_kind.h"
|
|
#include "llvm/ADT/Optional.h"
|
|
|
|
namespace Carbon {
|
|
|
|
// Given two operators `$` and `@`, and an expression `a $ b @ c`, how should
|
|
// the expression be parsed?
|
|
enum class OperatorPriority : int8_t {
|
|
// The left operator has higher precedence: `(a $ b) @ c`.
|
|
LeftFirst = -1,
|
|
// The expression is ambiguous.
|
|
Ambiguous = 0,
|
|
// The right operator has higher precedence: `a $ (b @ c)`.
|
|
RightFirst = 1,
|
|
};
|
|
|
|
enum class Associativity : int8_t {
|
|
LeftToRight = -1,
|
|
None = 0,
|
|
RightToLeft = 1
|
|
};
|
|
|
|
// A precedence group associated with an operator or expression.
|
|
class PrecedenceGroup {
|
|
private:
|
|
PrecedenceGroup(int8_t level) : level(level) {}
|
|
|
|
public:
|
|
// Objects of this type should only be constructed using the static factory
|
|
// functions below.
|
|
PrecedenceGroup() = delete;
|
|
|
|
// Get the sentinel precedence level for a postfix expression. All operators
|
|
// should have lower precedence than this.
|
|
static auto ForPostfixExpression() -> PrecedenceGroup;
|
|
|
|
// Get the sentinel precedence level for a top-level expression context. All
|
|
// operators should have higher precedence than this.
|
|
static auto ForTopLevelExpression() -> PrecedenceGroup;
|
|
|
|
// Look up the operator information of the given prefix operator token, or
|
|
// return llvm::None if the given token is not a prefix operator.
|
|
static auto ForLeading(TokenKind kind) -> llvm::Optional<PrecedenceGroup>;
|
|
|
|
struct Trailing;
|
|
|
|
// Look up the operator information of the given infix or postfix operator
|
|
// token, or return llvm::None if the given token is not an infix or postfix
|
|
// operator.
|
|
static auto ForTrailing(TokenKind kind) -> llvm::Optional<Trailing>;
|
|
|
|
friend auto operator==(PrecedenceGroup lhs, PrecedenceGroup rhs) -> bool {
|
|
return lhs.level == rhs.level;
|
|
}
|
|
friend auto operator!=(PrecedenceGroup lhs, PrecedenceGroup rhs) -> bool {
|
|
return lhs.level != rhs.level;
|
|
}
|
|
|
|
// Compare the precedence levels for two adjacent operators.
|
|
static auto GetPriority(PrecedenceGroup left, PrecedenceGroup right)
|
|
-> OperatorPriority;
|
|
|
|
// Get the associativity of this precedence group.
|
|
Associativity GetAssociativity() const {
|
|
return static_cast<Associativity>(GetPriority(*this, *this));
|
|
}
|
|
|
|
private:
|
|
// The precedence level.
|
|
int8_t level;
|
|
};
|
|
|
|
// Precedence information for a trailing operator.
|
|
struct PrecedenceGroup::Trailing {
|
|
// The precedence level.
|
|
PrecedenceGroup level;
|
|
// `true` if this is an infix binary operator, `false` if this is a postfix
|
|
// unary operator.
|
|
bool is_binary;
|
|
};
|
|
|
|
} // namespace Carbon
|
|
|
|
#endif // PARSER_PRECEDENCE_H_
|