– This file contains the parser, which converts text into abstract syntax trees lpeg = require ‘lpeg’ re = require ‘re’ lpeg.setmaxstack 20000 {:P,:R,:S,:C,:Cmt,:Carg,:Cc} = lpeg

– foldr {A{a1,a2,…},B{b1,b2,…},C{c1,c2,…}} -> C{B{A{a1,a2,…},b1,b2…},c1,c2…} foldr = (…)-> inner = select(1,…) for i=2,select(‘#’,…) do assert inner.type outer = select(i,…) table.insert(outer, 1, inner) outer.source.start = inner.source.start inner = outer assert inner.type return inner

DEFS = with {} – Newline supports either windows-style CR+LF or unix-style LF .nl = P(“\r”)^-1 * P(“\n”) .tab = P(“\t”) .atbreak = lpeg.B(lpeg.S(“;,. \r\n\t({[“)) + -lpeg.B(1) .tonumber = tonumber .tochar = string.char .unpack = unpack or table.unpack .nil = Cc(nil) .userdata = Carg(1) – Always match and capture the indentation (spaces only) of the current line – i.e. the leading space of the chunk of non-newline characters leading up to s[i] .indentation = lpeg.Cmt P(0), (s, i)-> sub = string.sub while i > 1 and sub(s,i-1,i-1) != ‘\n’ do i -= 1 return true, (s\match(“^ *”, i)) .utf8char = ( R(“\194\223”)R(“\128\191”) + R(“\224\239”)R(“\128\191”)R(“\128\191”) + R(“\240\244”)R(“\128\191”)R(“\128\191”)R(“\128\191”)) .operatorchar = S(“#’`~@^&*+=<>?/%!|\-”) + (P(“\xE2”) * (R(“\x88\x8B”)+R(“\xA8\xAB”)) * R(“\128\191”)) .Tree = (t, userdata)-> userdata.maketree(t, userdata) .foldr = foldr

setmetatable(DEFS, {_index:(key)=> if i = key\match(“^ascii(%d+)$”) c = string.char(tonumber(i)) self[key] = c return c elseif i = key\match(“^number_(%d+)$”) p = Cc(tonumber(i)) self[key] = p return p })

– Just for cleanliness, I put the language spec in its own file using a slightly – extended version of the lpeg.re syntax. pegtidier = re.compile [[ file <- %nl* {~ (captureddef/line) (%nl+ (captureddef/line))* %nl* ~} ident <- [a-zA-Z][a-zA-Z0-9]* line <- [^%nl]* captureddef <- ({ident} (“ “) “(“ {ident} “)” (“ “) “<-” {[^%nl]* (%nl+ “ “+ [^%nl])}) -> “%1 <- ({| {:type:’’->’%2’:} {:start:{}:} (%3) {:stop:{}:} |} %%userdata) -> Tree” ]]

makeparser = (peg, maketree=nil)-> peg = assert(pegtidier\match(peg)) peg = assert(re.compile(peg, DEFS)) return (input, filename=’???’)-> input = tostring(input) treemt = {_index: {source:input, filename:filename}} userdata = { maketree: maketree or ((t)->setmetatable(t, treemt)) :filename, file:input } tree = peg\match(input, nil, userdata) if not tree or type(tree) == ‘number’ error “File #{filename} failed to parse:\n#{input}” return tree

return make_parser