type pos = int

type svalue = Tokens.svalue
type ('a,'b) token = ('a,'b) Tokens.token
type lexresult = (svalue,pos) token

val lineNum = ErrorMsg.lineNum
val linePos = ErrorMsg.linePos
val commentDepth = ref 0;
val stringAcc = ref "";
val stringBeg = ref 0;
fun err(p1,p2) = ErrorMsg.error p1

local 
 fun exp (n, 0) = 1
   | exp (n, y) = n * exp (n, y-1);
in
fun stol (#"\\"::tail) = stol(tail)
	|stol (n::[]) = ord (n) - ord (#"0")
	| stol (n::tail) = (ord(n) - ord (#"0"))
	* exp (10, length(tail)) + stol(tail)
	| stol ([]) = 0;
end;

fun accumulateString (s) = (stringAcc := String.concat [!stringAcc, s]);

fun eof() = let val pos = hd(!linePos) in Tokens.EOF(pos,pos) end
%%

alnum=[A-Za-z0-9_];
digit=[0-9];
%s COMMENT;
%s STRING;
%header (functor TigerLexFun(structure Tokens : Tiger_TOKENS));
%%
<INITIAL>"\n"	=> (lineNum := !lineNum+1; linePos := yypos :: !linePos; continue());
<INITIAL>" "    => (lex());
<INITIAL>"\t"	=> (lex());
<INITIAL>{digit}+ => (let val strlist= explode yytext
                      in
                      Tokens.INT(stol(strlist), yypos, length strlist)
                      end);
<INITIAL>","	=> (Tokens.COMMA(yypos,yypos+1));
<INITIAL>"type"  => (Tokens.TYPE(yypos,yypos+4));
<INITIAL>"var"  	=> (Tokens.VAR(yypos,yypos+3));
<INITIAL>"function"    => (Tokens.FUNCTION(yypos,yypos+8));
<INITIAL>"break" => (Tokens.BREAK(yypos,yypos+5));
<INITIAL>"of"  	=> (Tokens.OF(yypos,yypos+2));
<INITIAL>"end"  	=> (Tokens.END(yypos,yypos+3));
<INITIAL>"in"  	=> (Tokens.IN(yypos,yypos+2));
<INITIAL>"nil"  	=> (Tokens.NIL(yypos,yypos+3));
<INITIAL>"let"  	=> (Tokens.LET(yypos,yypos+3));
<INITIAL>"do"  	=> (Tokens.DO(yypos,yypos+2));
<INITIAL>"to"  	=> (Tokens.TO(yypos,yypos+2));
<INITIAL>"for"  	=> (Tokens.FOR(yypos,yypos+3));
<INITIAL>"while"  	=> (Tokens.WHILE(yypos,yypos+5));
<INITIAL>"else"	=> (Tokens.ELSE(yypos,yypos+4));
<INITIAL>"then"	=> (Tokens.THEN(yypos,yypos+4));
<INITIAL>"if"  	=> (Tokens.IF(yypos,yypos+2));
<INITIAL>"array"	=> (Tokens.ARRAY(yypos,yypos+5));
<INITIAL>[A-Za-z]{alnum}* => (Tokens.ID(yytext,yypos, yypos + (length (explode yytext))));
<INITIAL>"|"     => (Tokens.OR(yypos,yypos+1));
<INITIAL>"&"     => (Tokens.AND(yypos,yypos+1));
<INITIAL>"="     => (Tokens.EQ(yypos,yypos+1));
<INITIAL>":="    => (Tokens.ASSIGN(yypos,yypos+2));
<INITIAL>":"     => (Tokens.COLON(yypos, yypos+1));
<INITIAL>"+"     => (Tokens.PLUS(yypos, yypos+1));
<INITIAL>"-"     => (Tokens.MINUS(yypos, yypos+1));
<INITIAL>"*"     => (Tokens.TIMES(yypos, yypos+1));
<INITIAL>"/"     => (Tokens.DIVIDE(yypos, yypos+1));
<INITIAL>"<>"     => (Tokens.NEQ(yypos, yypos+1));
<INITIAL>">"     => (Tokens.GT(yypos, yypos+1));
<INITIAL>"<"     => (Tokens.LT(yypos, yypos+1));
<INITIAL>">="    => (Tokens.GE(yypos, yypos+1));
<INITIAL>"<="    => (Tokens.LE(yypos, yypos+1));
<INITIAL>"["     => (Tokens.LBRACK(yypos, yypos+1));
<INITIAL>"{"     => (Tokens.LBRACE(yypos, yypos+1));
<INITIAL>"("     => (Tokens.LPAREN(yypos, yypos+1));
<INITIAL>")"     => (Tokens.RPAREN(yypos, yypos+1)); 
<INITIAL>"}"     => (Tokens.RBRACE(yypos, yypos+1)); 
<INITIAL>"]"     => (Tokens.RBRACK(yypos, yypos+1));
<INITIAL>"."     => (Tokens.DOT(yypos, yypos+1));
<INITIAL>";"     => (Tokens.SEMICOLON(yypos, yypos+1) (* note the sign of cancer *));
<INITIAL>"/*"    => (YYBEGIN COMMENT; commentDepth := 1; lex());
<COMMENT>"*/"    => (if !commentDepth = 1 then (YYBEGIN INITIAL; lex())
		     else (commentDepth := !commentDepth-1; lex()));
<COMMENT>"\n"    => (lineNum := !lineNum+1; lex());
<COMMENT>.       => (lex());
<INITIAL>"\""    => (YYBEGIN STRING; stringAcc := ""; stringBeg := yypos; lex());
<STRING>"\""     => (YYBEGIN INITIAL;
		     Tokens.STRING(!stringAcc,
				   !stringBeg,
				   !stringBeg +length (explode (!stringAcc))));
<STRING>"\\a"    => (accumulateString("\a"); lex());
<STRING>"\\b"    => (accumulateString("\b"); lex());
<STRING>"\\f"    => (accumulateString("\f"); lex());
<STRING>"\\n"    => (accumulateString("\n"); lex());
<STRING>"\\r"    => (accumulateString("\r"); lex());
<STRING>"\\t"    => (accumulateString("\t"); lex());
<STRING>"\\\\"   => (accumulateString("\\"); lex());

<STRING>"\\^"[@-Z] => (
	accumulateString(
		implode [chr(ord(hd(tl(tl(explode yytext)))) - 64)]);
	lex());
<STRING>"\\^"[a-z] => (
	accumulateString(
		implode [chr(ord(hd(tl (tl(explode yytext)))) - 96)]);
	lex());
<STRING>"\\v"    => (accumulateString("\v"); lex());
<STRING>.        => (accumulateString(yytext); lex());
<STRING>\\ {digit}{3} => (accumulateString(implode ([chr(stol (explode yytext))])); lex());
<STRING>\\(\n | \t | \  | \014 )+\\ =>  (lex());
.       => (ErrorMsg.error yypos ("illegal character " ^ yytext); continue());