Fix parse error when keyword is followed by underscore

For example "do_something" was a parse error, due a confusion with the
"do" keyword.
Also, some more code cleanup.

src/ast.fs

 module Ast
 
 open System.Collections.Generic
+open System.IO
 
 type targetOutput = Text | CHeader | CList | JS | Nasm
 
 let version = "1.1.5" // Shader Minifer version
-let debugMode = false
+let debugMode = true
+
+let nullOut = new StreamWriter(Stream.Null) :> TextWriter
 
 let mutable outputName = "shader_code.h"
 let mutable targetOutput = CHeader
@@ -93,10 +96,10 @@ let mapEnv fe fi = {fExpr = fe; fInstr = fi; vars = Map.empty}
 
 let foldList env fct li =
   let env = ref env
-  let res = li |> List.map ((fun i -> // FIXME: use List.fold is cleaner :)
+  let res = li |> List.map (fun i -> // FIXME: use List.fold is cleaner :)
     let x = fct !env i
     env := fst x
-    snd x) : 'a -> 'a)
+    snd x)
   !env, res
 
 // Applies env.fExpr recursively on all nodes of an expression.

src/cGen.fs

@@ -55,7 +55,7 @@ let printHeader data asAList =
 
 let printNoHeader data =
   use out = output()
-  let str = [for _,code in data -> Printer.print code] |> String.concat "\n"
+  let str = [for _, code in data -> Printer.print code] |> String.concat "\n"
   fprintf out "%s" str
 
 let printJSHeader data =
@@ -95,8 +95,7 @@ let printNasmHeader data =
     fprintfn out "_%s:\r\n\tdb '%s', 0" name (Printer.print code)
     fprintfn out ""
 
-let print data =
-    match Ast.targetOutput with
+let print data = function
     | Ast.Text -> printNoHeader data
     | Ast.CHeader -> printHeader data false
     | Ast.CList -> printHeader data true

src/main.fs

@@ -26,7 +26,7 @@ let nullOut = new StreamWriter(Stream.Null) :> TextWriter
 
 // like printf when verbose option is set
 let vprintf fmt =
-  let out = if Ast.verbose then stdout else nullOut
+  let out = if Ast.verbose then stdout else Ast.nullOut
   fprintf out fmt
 
 let printSize code =
@@ -52,9 +52,7 @@ let readFile file =
         else new StreamReader(file)
     stream.ReadToEnd()
 
-let minify file =
-  let content = readFile file
-  let filename = if file = "" then "stdin" else file
+let minify filename (content: string) =
   vprintf "Input file size is: %d\n" (content.Length)
   let code = Parse.runParser filename content
   vprintf "File parsed. "; printSize code
@@ -68,17 +66,22 @@ let minify file =
       if Ast.noRenaming then code
       else rename code
 
-  vprintf "Minification of '%s' finished.\n" file
+  vprintf "Minification of '%s' finished.\n" filename
   code
 
+let minifyFile file =
+  let content = readFile file
+  let filename = if file = "" then "stdin" else file
+  minify filename content
+
 let run files =
   let fail (exn:exn) s =
         printfn "%s" s;
         printfn "%s" exn.StackTrace
         1
   try
-    let codes = Array.map minify files
-    CGen.print (Array.zip files codes)
+    let codes = Array.map minifyFile files
+    CGen.print (Array.zip files codes) Ast.targetOutput
     0
   with
     | Failure s as exn -> fail exn s
@@ -124,7 +127,7 @@ let () =
      //"--macro-threshold", ArgType.Int (fun i ->
      //    printfn "Macros are disabled in the release."; Ast.macroThreshold <- i), "[disabled] Use a #define macro if it can save at least <int> bytes"
      "--", ArgType.Rest setFile, "Stop parsing command line"
-    ] |> List.map (fun (s, f, d) -> ArgInfo(s, f, d))
+    ] |> List.map ArgInfo
 
   ArgParser.Parse(specs, setFile)
   files := List.rev !files

src/parse.fs

@@ -143,7 +143,7 @@ module private ParseImpl =
     let statement, stmtRef = createParserForwardedToRef()
     let declaration, declRef = createParserForwardedToRef()
 
-    let keyword s = attempt (pstring s .>> notFollowedBy letter .>> notFollowedBy digit) .>> ws
+    let keyword s = attempt (pstring s .>> notFollowedBy letter .>> notFollowedBy digit .>> notFollowedBy (ch '_')) .>> ws
 
     // A type block, like struct or interface blocks
     let blockSpecifier prefix =