1 files changed, 64 insertions, 0 deletions
diff --git a/parser.moon b/parser.moon
new file mode 100644
index 0000000..9a2e2ff
--- /dev/null
+++ b/parser.moon
@@ -0,0 +1,64 @@
+-- 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
+{:repr} = require 'utils'
+
+DEFS = with {}
+    -- Newline supports either windows-style CR+LF or unix-style LF
+    .nl = P("\r")^-1 * P("\n")
+    .tab = P("\t")
+    .tonumber = tonumber
+    .tochar = string.char
+    .unpack = unpack or table.unpack
+    .nil = Cc(nil)
+    .userdata = Carg(1)
+    .utf8_char = (
+        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"))
+    .Tree = (t, userdata)-> userdata.make_tree(t, userdata)
+
+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 modified
+-- version of the lpeg.re syntax.
+peg_tidier = re.compile [[
+file <- %nl* {~ (def/comment) (%nl+ (def/comment))* %nl* ~}
+def <- anon_def / captured_def
+anon_def <-
+    ({ident} (" "*) ":" {[^%nl]* (%nl+ " "+ [^%nl]*)*}) 
+    -> "%1 <- %2"
+captured_def <-
+    ({ident} (" "*) "(" {ident} ")" (" "*) ":" {[^%nl]* (%nl+ " "+ [^%nl]*)*})
+    -> "%1 <- ({| {:start:{}:} %3 {:stop:{}:} {:type: (''->'%2') :} |} %%userdata) -> Tree"
+ident <- [a-zA-Z_][a-zA-Z0-9_]*
+comment <- "--" [^%nl]*
+]]
+
+make_parser = (peg, make_tree=nil)->
+    peg = assert(peg_tidier\match(peg))
+    peg = assert(re.compile(peg, DEFS))
+    return (input, filename='???')->
+        input = tostring(input)
+        tree_mt = {__index: {source:input, filename:filename}}
+        userdata = {
+            make_tree: make_tree or ((t)->setmetatable(t, tree_mt))
+            :filename, source:input
+        }
+        tree = peg\match(input, nil, userdata)
+        if not tree
+            error "File #{filename} failed to parse:\n#{input}"
+        return tree
+
+return make_parser