initial

.gitignore

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+_build/
+*.byte
+*.native

README.md

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+# micro
+
+A minimal compiler in ML, as seen in [this tutorial](http://troydm.github.io/blog/2014/03/29/writing-micro-compiler-in-ocaml/).
+
+Work in progess.

src/codegen.ml

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+type generator = { vars: (string, int) Hashtbl.t; file: string; chan: out_channel }
+
+let new_generator file =
+  let fs = (Filename.chop_extension file) ^ ".s" in
+    { vars=Hashtbl.create 100; file=fs; chan=open_out fs }
+
+let close_generator g = close_out g.chan
+
+let gen g v = output_string g.chan v; output_string g.chan "\n"
+
+let bottom_var _ g =
+  Hashtbl.fold (fun _ v c -> if v >= c then (v+4) else c) g.vars 0
+
+let empty_var s g i = (bottom_var s g) + 4 * (i - 1)
+
+let var_addr s g v =
+  if String.length v > 6 && String.sub v 0 6 = "__temp"
+      then
+        let i = String.sub v 6 ((String.length v) - 6) in "[esp+" ^ i ^ "]"
+      else
+        try "[esp+" ^ string_of_int (Hashtbl.find g.vars v) ^ "]"
+        with Not_found -> syntax_error s ("identifier " ^ v ^ " not defined")
+
+let var s g v = "dword " ^ (var_addr s g v)
+
+let temp_var s g i =
+  Token.Identifier ("__temp" ^ (string_of_int (empty_var s g i)))
+
+let is_alloc_var _ g v = Hashtbl.mem g.vars v
+
+let alloc_var s g v =
+  if is_alloc_var s g v
+    then var s g v
+    else let _ = Hashtbl.replace g.vars v (empty_var s g 1) in var s g v
+
+let token_var s g v =
+  match v with
+    | Token.Identifier i -> var s g i
+    | _ -> syntax_error s "identifier expected"
+
+let unop g opcode a = gen g ("    " ^ opcode ^ " " ^ a)
+
+let binop g opcode a b = gen g ("    " ^ opcode ^ " " ^ a ^ ", " ^ b)
+
+let push g a = op g "push" a
+
+

src/compile.ml

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+let compile file =
+  try
+    let g = Codegen.new_generator file in
+    let s = Stream.open_stream file in
+    let o = Filename.chop_extension file in
+    parse s g;
+    Stream.close_stream s;
+    Codegen.close_generator g;
+    let _ = Sys.command ("nasm -f macho " ^ g.file) in
+    let _ = Sys.command ("gcc -o " ^out ^ " " ^ out ^ ".o") in
+    ()
+  with
+    | Syntax_error e ->
+      printf "syntax error: %s\n" e;
+    | Sys_error _ ->
+      print_string "no file found\n"
+
+let help name = printf "%s <file>\n" name
+
+let () =
+  if Array.length Sys.argv = 1
+    then help (Array.get Sys.argv 0)
+    else
+      let file = Array.get Sys.argv 1 in
+        printf "compiling %s\n" file
+        compile file

src/parse.ml

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+let parse stm g =
+  let s = (Token.new_scanner stm) in
+      try
+          Token.program s g
+      with End_of_file ->
+        Token.syntax_error s "program reached end of file before end keyword"
+
+let program s g =
+  if Token.match_token s Token.Begin then
+      let _ = generate_begin s g in
+      let _ = statements s g in
+      if Token.match_token s Token.End then
+      let _ = generate_end s g in ()
+      else Token.syntax_error s "program should end with end keyword"
+  else Token.syntax_error s "program should start with begin keyword"
+
+let rec statements s g = if statement s g then statements s g else ()
+
+let statement s g =
+  let t = next_token s in
+    if match t with
+      | Token.Read -> read s g
+      | Token.Write -> write s g
+      | Token.Identifier i -> assignment s g
+      | _ -> false
+    then
+        if Token.match_token s Token.Semicolon then true
+        else Token.syntax_error s "statement must end with semicolon"
+    else false

src/stream.ml

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+type stream = { mutable chr: char option; mutable line_num: int; chan: in_channel }
+
+let open_stream file = { chr=None; line_num=1; chan=open_in file }
+
+let close_stream stm = close_in stm.chan
+
+let read_char stm =
+  match stm.chr with 
+    | None ->
+      let c = input_char stm.chan in
+        if c = '\n'
+          then let _ = stm.line_num <- stm.line_num + 1 in c
+          else c
+    | Some c -> stm.chr <- None; c
+
+let unread_char stm c = stm.chr <- Some c
+
+let is_digit c =
+  let code = Char.code c in code >= Char.code('0') && code <= Char.code('9')
+
+let is_alpha c =
+  let code = Char.code c in
+    (code >= Char.code('A') && code <= Char.code('Z')) ||
+    (code >= Char.code('a') && code <= Char.code('z'))

src/token.ml

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+type token = Begin
+           | End
+           | Identifier of string
+           | Read
+           | Write
+           | Literal of int
+           | Assign
+           | LeftParen
+           | RightParen
+           | Add
+           | Sub
+           | Comma
+           | Semicolon
+
+type scanner = { mutable last_token: token option; stm: Stream.stream }
+
+exception Syntax_error of string
+
+let syntax_error s msg =
+  raise (Syntax_error (msg ^" on line " ^ (string_of_int s.stm.line_num)))
+
+let rec skip_blank_chars stm =
+  let c = Stream.read_char stm in
+    match c with
+      | ' ' | '\t' | '\r' | '\n' -> skip_blank_chars stm
+      | _ -> Stream.unread_char stm c; ()
+
+let scan s =
+  let stm = s.stm in
+  let c = Stream.read_char stm in
+  let rec scan_iden acc =
+    let nc = Stream.read_char stm in
+      if Stream.is_alpha nc || Stream.is_digit nc || nc='_'
+         then scan_iden (acc ^ (Char.escaped nc))
+         else let _ = Stream.unread_char stm nc in
+              let lc = String.lowercase acc in
+              if lc = "begin" then Begin
+              else if lc = "end" then End
+              else if lc = "read" then Read
+              else if lc = "write" then Write
+              else Identifier acc
+   in
+   let rec scan_lit acc =
+    let nc = Stream.read_char stm in
+        if Stream.is_digit nc
+        then scan_lit (acc ^ (Char.escaped nc))
+        else let _ = Stream.unread_char stm nc in
+             Literal (int_of_string acc)
+   in
+   if Stream.is_alpha c then scan_iden (Char.escaped c)
+   else if Stream.is_digit c then scan_lit (Char.escaped c)
+   else if c='+' then Add
+   else if c='-' then Sub
+   else if c=',' then Comma
+   else if c=';' then Semicolon
+   else if c='(' then LeftParen
+   else if c=')' then RightParen
+   else if c=':' && Stream.read_char stm = '=' then Assign
+   else syntax_error s "Could not identify token"