fb1-4.l

/* Companion source code for "flex & bison", published by O'Reilly
 * Media, ISBN 978-0-596-15597-1
 * Copyright (c) 2009, Taughannock Networks. All rights reserved.
 * See the README file for license conditions and contact info.
 * $Header: /home/johnl/flnb/code/RCS/fb1-4.l,v 2.1 2009/11/08 02:53:18 johnl Exp $
 */

/* recognize tokens for the calculator and print them out */

%{
   enum yytokentype {
     NUMBER = 258,
     ADD = 259,
     SUB = 260,
     MUL = 261,
     DIV = 262,
     ABS = 263,
     EOL = 264 /* end of line */
   };

   int yylval;

%}

%%
"+"	{ return ADD; }
"-"	{ return SUB; }
"*"	{ return MUL; }
"/"	{ return DIV; }
"|"     { return ABS; }
[0-9]+	{ yylval = atoi(yytext); return NUMBER; }
\n      { return EOL; }
[ \t]   { /* ignore white space */ }
.	{ printf("Mystery character %c\n", *yytext); }
%%
main()
{
  int tok;

  while(tok = yylex()) {
    printf("%d", tok);
    if(tok == NUMBER) printf(" = %d\n", yylval);
    else printf("\n");
  }
}