lexer: add lexer for Faust

Faust is a DSP (digital signal processing) programming language.
See http://faust.grame.fr/

Closes #125

1 files changed, 57 insertions, 0 deletions

diff --git a/lexers/faust.lua b/lexers/faust.lua
new file mode 100644
index 0000000..e9c7162
--- /dev/null
+++ b/lexers/faust.lua
@@ -0,0 +1,57 @@
+-- Faust LPeg lexer.
+
+local l = require('lexer')
+local token, word_match = l.token, l.word_match
+local P, R, S = lpeg.P, lpeg.R, lpeg.S
+
+local M = {_NAME = 'faust'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments.
+local line_comment = '//' * l.nonnewline^0
+local block_comment = '/*' * (l.any - '*/')^0 * P('*/')^-1
+local comment = token(l.COMMENT, line_comment + block_comment)
+
+-- Strings.
+local string = token(l.STRING, l.delimited_range('"', true))
+
+-- Numbers.
+local int = R('09')^1
+local rad = P('.')
+local exp = (P('e') * S('+-')^-1 * int)^-1
+local flt = int * (rad * int)^-1 * exp + int^-1 * rad * int * exp
+local number = token(l.NUMBER, flt + int)
+
+-- Keywords.
+local keyword = token(l.KEYWORD, word_match{
+  'declare', 'import', 'mdoctags', 'dependencies', 'distributed',
+  'inputs', 'outputs', 'par', 'seq', 'sum', 'prod', 'xor', 'with',
+  'environment', 'library', 'component', 'ffunction', 'fvariable',
+  'fconstant', 'int', 'float', 'case', 'waveform', 'h:', 'v:', 't:'
+})
+
+-- Identifiers.
+local identifier = token(l.IDENTIFIER, l.word)
+
+-- Operators.
+local punct = S('+-/*%<>~!=^&|?~:;,.()[]{}@#$`\\\'')
+local operator = token(l.OPERATOR, punct)
+
+-- Pragmas.
+local mdoc = P('<mdoc>') * (l.any - P('</mdoc>'))^0 * P('</mdoc>')
+local pragma = token(l.PREPROCESSOR, mdoc)
+
+M._rules = {
+  {'whitespace', ws},
+  {'comment', comment},
+  {'pragma', pragma},
+  {'keyword', keyword},
+  {'number', number},
+  {'operator', operator},
+  {'identifier', identifier},
+  {'string', string},
+}
+
+return M