parser/lisp/init.lua

   1 require'lpeg'
   2 local lpeg = lpeg
   3 local P, S = lpeg.P, lpeg.S
   4 local cwd = (...):match'(.-)[^%.]+$'
   5 local l = require(cwd..'_lexer')
   6
   7 -- The LPeg patterns for atoms are taken from the scintillua lexer:
   8 -- Copyright 2006-2017 Mitchell mitchell.att.foicica.com.
   9
  10 local macro_prefix = P('#.') + ',@' + ',.' + ',' + '`' + "'"
  11
  12 local opposite = {
  13         ["("] = ")",
  14         [")"] = "(",
  15         ['"'] = '"',
  16         ["|"] = "|",
  17         [";"]  = "\n",
  18         ["#|"] = "|#",
  19 }
  20
  21 local number = P('-')^-1 * l.digit^1 * (S('./') * l.digit^1)^-1
  22 local word = l.alpha * (l.alnum + '_' + '-')^0
  23 local entity = '&' * word
  24 local identifier = word
  25
  26 return {
  27         prefix = macro_prefix,
  28         opposite = opposite,
  29         atom = function(pfx) return pfx * identifier + number + entity + "..." + "." end,
  30         word = number + identifier + "\\" * l.any
  31 }