mlyacc/examples/calc/calc.lex

   1 structure Tokens = Tokens
   2
   3 type pos = int
   4 type svalue = Tokens.svalue
   5 type ('a,'b) token = ('a,'b) Tokens.token
   6 type lexresult= (svalue,pos) token
   7
   8 val pos = ref 0
   9 fun eof () = Tokens.EOF(!pos,!pos)
  10 fun error (e,l : int,_) = TextIO.output (TextIO.stdOut, String.concat[
  11         "line ", (Int.toString l), ": ", e, "\n"
  12       ])
  13
  14 %%
  15 %header (functor CalcLexFun(structure Tokens: Calc_TOKENS));
  16 alpha=[A-Za-z];
  17 digit=[0-9];
  18 ws = [\ \t];
  19 %%
  20 \n       => (pos := (!pos) + 1; lex());
  21 {ws}+    => (lex());
  22 {digit}+ => (Tokens.NUM (valOf (Int.fromString yytext), !pos, !pos));
  23
  24 "+"      => (Tokens.PLUS(!pos,!pos));
  25 "*"      => (Tokens.TIMES(!pos,!pos));
  26 ";"      => (Tokens.SEMI(!pos,!pos));
  27 {alpha}+ => (if yytext="print"
  28                  then Tokens.PRINT(!pos,!pos)
  29                  else Tokens.ID(yytext,!pos,!pos)
  30             );
  31 "-"      => (Tokens.SUB(!pos,!pos));
  32 "^"      => (Tokens.CARAT(!pos,!pos));
  33 "/"      => (Tokens.DIV(!pos,!pos));
  34 "."      => (error ("ignoring bad character "^yytext,!pos,!pos);
  35              lex());