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// Package token defines constants representing the lexical tokens of JavaScript (ECMA5).
package token
import (
"strconv"
)
// Token is the set of lexical tokens in JavaScript (ECMA5).
type Token int
// String returns the string corresponding to the token.
// For operators, delimiters, and keywords the string is the actual
// token string (e.g., for the token PLUS, the String() is
// "+"). For all other tokens the string corresponds to the token
// name (e.g. for the token IDENTIFIER, the string is "IDENTIFIER").
//
func (tkn Token) String() string {
if 0 == tkn {
return "UNKNOWN"
}
if tkn < Token(len(token2string)) {
return token2string[tkn]
}
return "token(" + strconv.Itoa(int(tkn)) + ")"
}
// This is not used for anything
func (tkn Token) precedence(in bool) int {
switch tkn {
case LOGICAL_OR:
return 1
case LOGICAL_AND:
return 2
case OR, OR_ASSIGN:
return 3
case EXCLUSIVE_OR:
return 4
case AND, AND_ASSIGN, AND_NOT, AND_NOT_ASSIGN:
return 5
case EQUAL,
NOT_EQUAL,
STRICT_EQUAL,
STRICT_NOT_EQUAL:
return 6
case LESS, GREATER, LESS_OR_EQUAL, GREATER_OR_EQUAL, INSTANCEOF:
return 7
case IN:
if in {
return 7
}
return 0
case SHIFT_LEFT, SHIFT_RIGHT, UNSIGNED_SHIFT_RIGHT:
fallthrough
case SHIFT_LEFT_ASSIGN, SHIFT_RIGHT_ASSIGN, UNSIGNED_SHIFT_RIGHT_ASSIGN:
return 8
case PLUS, MINUS, ADD_ASSIGN, SUBTRACT_ASSIGN:
return 9
case MULTIPLY, SLASH, REMAINDER, MULTIPLY_ASSIGN, QUOTIENT_ASSIGN, REMAINDER_ASSIGN:
return 11
}
return 0
}
type _keyword struct {
token Token
futureKeyword bool
strict bool
}
// IsKeyword returns the keyword token if literal is a keyword, a KEYWORD token
// if the literal is a future keyword (const, let, class, super, ...), or 0 if the literal is not a keyword.
//
// If the literal is a keyword, IsKeyword returns a second value indicating if the literal
// is considered a future keyword in strict-mode only.
//
// 7.6.1.2 Future Reserved Words:
//
// const
// class
// enum
// export
// extends
// import
// super
//
// 7.6.1.2 Future Reserved Words (strict):
//
// implements
// interface
// let
// package
// private
// protected
// public
// static
//
func IsKeyword(literal string) (Token, bool) {
if keyword, exists := keywordTable[literal]; exists {
if keyword.futureKeyword {
return KEYWORD, keyword.strict
}
return keyword.token, false
}
return 0, false
}
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