-- Copyright 2006-2018 Mitchell mitchell.att.foicica.com. See License.txt.
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-- Forth LPeg lexer.
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-- Contributions from Joseph Eib.
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local lexer = require('lexer')
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local token, word_match = lexer.token, lexer.word_match
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local P, R, S = lpeg.P, lpeg.R, lpeg.S
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local lex = lexer.new('forth')
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-- Whitespace.
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lex:add_rule('whitespace', token(lexer.WHITESPACE, lexer.space^1))
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-- Strings.
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local c_str = 'c' * lexer.delimited_range('"', true, true)
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local s_str = 's' * lexer.delimited_range('"', true, true)
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local s_bs_str = 's\\' * lexer.delimited_range('"', true, false)
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local dot_str = '.' * lexer.delimited_range('"', true, true)
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local dot_paren_str = '.' * lexer.delimited_range('()', true, true, false)
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local abort_str = 'abort' * lexer.delimited_range('"', true, true)
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lex:add_rule('string', token(lexer.STRING, c_str + s_str + s_bs_str + dot_str +
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dot_paren_str + abort_str))
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-- Keywords.
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lex:add_rule('keyword', token(lexer.KEYWORD, word_match[[
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#> #s */ */mod +loop , . .r /mod 0< 0<> 0> 0= 1+ 1- 2! 2* 2/ 2>r 2@ 2drop 2dup
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2over 2r> 2r@ 2swap :noname <# <> >body >in >number >r ?do ?dup @ abort abs
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accept action-of again align aligned allot and base begin bl buffer: c! c, c@
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case cell+ cells char char+ chars compile, constant, count cr create decimal
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defer defer! defer@ depth do does> drop dup else emit endcase endof
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environment? erase evaluate execute exit false fill find fm/mod here hex hold
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holds i if immediate invert is j key leave literal loop lshift m* marker max
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min mod move negate nip of or over pad parse parse-name pick postpone quit r>
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r@ recurse refill restore-input roll rot rshift s>d save-input sign sm/rem
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source source-id space spaces state swap to then true tuck type u. u.r u> u<
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um* um/mod unloop until unused value variable while within word xor ['] [char]
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[compile]
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]], true))
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-- Identifiers.
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lex:add_rule('identifier', token(lexer.IDENTIFIER, (lexer.alnum +
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S('+-*=<>.?/\'%,_$#'))^1))
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-- Comments.
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local line_comment = S('|\\') * lexer.nonnewline^0
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local block_comment = '(' * (lexer.any - ')')^0 * P(')')^-1
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lex:add_rule('comment', token(lexer.COMMENT, line_comment + block_comment))
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-- Numbers.
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lex:add_rule('number', token(lexer.NUMBER, P('-')^-1 * lexer.digit^1 *
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(S('./') * lexer.digit^1)^-1))
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-- Operators.
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lex:add_rule('operator', token(lexer.OPERATOR, S(':;<>+*-/[]#')))
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return lex
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