1// Copyright 2009 The Go Authors. All rights reserved.
 2// Use of this source code is governed by a BSD-style
 3// license that can be found in the LICENSE file.
 4
 5// Package token defines constants representing the lexical tokens of the gcfg
 6// configuration syntax and basic operations on tokens (printing, predicates).
 7//
 8// Note that the API for the token package may change to accommodate new
 9// features or implementation changes in gcfg.
10//
11package token
12
13import "strconv"
14
15// Token is the set of lexical tokens of the gcfg configuration syntax.
16type Token int
17
18// The list of tokens.
19const (
20	// Special tokens
21	ILLEGAL Token = iota
22	EOF
23	COMMENT
24
25	literal_beg
26	// Identifiers and basic type literals
27	// (these tokens stand for classes of literals)
28	IDENT  // section-name, variable-name
29	STRING // "subsection-name", variable value
30	literal_end
31
32	operator_beg
33	// Operators and delimiters
34	ASSIGN // =
35	LBRACK // [
36	RBRACK // ]
37	EOL    // \n
38	operator_end
39)
40
41var tokens = [...]string{
42	ILLEGAL: "ILLEGAL",
43
44	EOF:     "EOF",
45	COMMENT: "COMMENT",
46
47	IDENT:  "IDENT",
48	STRING: "STRING",
49
50	ASSIGN: "=",
51	LBRACK: "[",
52	RBRACK: "]",
53	EOL:    "\n",
54}
55
56// String returns the string corresponding to the token tok.
57// For operators and delimiters, the string is the actual token character
58// sequence (e.g., for the token ASSIGN, the string is "="). For all other
59// tokens the string corresponds to the token constant name (e.g. for the
60// token IDENT, the string is "IDENT").
61//
62func (tok Token) String() string {
63	s := ""
64	if 0 <= tok && tok < Token(len(tokens)) {
65		s = tokens[tok]
66	}
67	if s == "" {
68		s = "token(" + strconv.Itoa(int(tok)) + ")"
69	}
70	return s
71}
72
73// Predicates
74
75// IsLiteral returns true for tokens corresponding to identifiers
76// and basic type literals; it returns false otherwise.
77//
78func (tok Token) IsLiteral() bool { return literal_beg < tok && tok < literal_end }
79
80// IsOperator returns true for tokens corresponding to operators and
81// delimiters; it returns false otherwise.
82//
83func (tok Token) IsOperator() bool { return operator_beg < tok && tok < operator_end }