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1local info = {
2    version   = 1.001,
3    comment   = "scintilla lpeg lexer for bnf",
4    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
5    copyright = "PRAGMA ADE / ConTeXt Development Team",
6    license   = "see context related readme files",
7}
8
9-- will replace the one in metafun
10
11local global, lpeg = _G, lpeg
12local P, R, S = lpeg.P, lpeg.R, lpeg.S
13
14local lexer       = require("scite-context-lexer")
15local context     = lexer.context
16local patterns    = context.patterns
17
18local token       = lexer.token
19local exact_match = lexer.exact_match
20
21local bnflexer    = lexer.new("bnf","scite-context-lexer-bnf")
22local whitespace  = bnflexer.whitespace
23
24-- from wikipedia:
25--
26-- <syntax>         ::= <rule> | <rule> <syntax>
27-- <rule>           ::= <opt-whitespace> "<" <rule-name> ">" <opt-whitespace> "::=" <opt-whitespace> <expression> <line-end>
28-- <opt-whitespace> ::= " " <opt-whitespace> | ""
29-- <expression>     ::= <list> | <list> <opt-whitespace> "|" <opt-whitespace> <expression>
30-- <line-end>       ::= <opt-whitespace> <EOL> | <line-end> <line-end>
31-- <list>           ::= <term> | <term> <opt-whitespace> <list>
32-- <term>           ::= <literal> | "<" <rule-name> ">"
33-- <literal>        ::= '"' <text1> '"' | "'" <text2> "'"
34-- <text1>          ::= "" | <character1> <text1>
35-- <text2>          ::= "" | <character2> <text2>
36-- <character>      ::= <letter> | <digit> | <symbol>
37-- <letter>         ::= "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" | "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z" | "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"
38-- <digit>          ::= "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
39-- <symbol>         ::= "|" | " " | "-" | "!" | "#" | "$" | "%" | "&" | "(" | ")" | "*" | "+" | "," | "-" | "." | "/" | ":" | ";" | ">" | "=" | "<" | "?" | "@" | "[" | "\" | "]" | "^" | "_" | "`" | "{" | "}" | "~"
40-- <character1>     ::= <character> | "'"
41-- <character2>     ::= <character> | '"'
42-- <rule-name>      ::= <letter> | <rule-name> <rule-char>
43-- <rule-char>      ::= <letter> | <digit> | "-"
44
45local anything  = patterns.anything
46local separator = P("|")
47local left      = P("<")
48local right     = P(">")
49local space     = S(" \t\n\r\f")
50local spaces    = space^1
51local letter    = R("AZ","az")
52local digit     = R("09")
53local symbol    = S([[| -!#$%&()*+,-./:;>=<?@[\]^_`{}~]])
54local text      = (letter + digit + symbol^0)
55local name      = letter * (letter + digit + P("-"))^0
56local becomes   = P("::=")
57local extra     = P("|")
58local single    = P("'")
59local double    = P('"')
60
61local t_spacing = token(whitespace,space^1)
62local t_term    = token("command",left)
63                * token("text",name)
64                * token("command",right)
65local t_text    = token("quote",single)
66                * token("text",text)
67                * token("quote",single)
68                + token("quote",double)
69                * token("text",text)
70                * token("quote",double)
71local t_becomes = token("operator",becomes)
72local t_extra   = token("extra",extra)
73local t_rest    = token("default",anything)
74
75bnflexer._rules = {
76    { "whitespace", t_spacing },
77    { "term",       t_term    },
78    { "text",       t_text    },
79    { "becomes",    t_becomes },
80    { "extra",      t_extra   },
81    { "rest",       t_rest    },
82}
83
84bnflexer._tokenstyles = context.styleset
85
86bnflexer._foldpattern = left + right
87
88bnflexer._foldsymbols = {
89    _patterns = {
90        "<",
91        ">",
92    },
93    ["grouping"] = {
94        ["<"] =  1,
95        [">"] = -1,
96    },
97}
98
99return bnflexer
100