/* scanner for a toy Pascal-like language */
%{
#include <math.h> /* needed for call to atof() */
%}
DIG [0-9]
ID    [a-z][a-z0-9]*
%%
{DIG}+                  printf("Integer: %s (%d)\n", yytext, atoi(yytext));
{DIG}+"."{DIG}*         printf("Float: %s (%g)\n", yytext, atof(yytext)); 
if|then|begin|end       printf("Keyword: %s\n",yytext);
"("                     printf("Open paren\n");
")"                     printf("Open paren\n");
{ID}                    printf("Identifier: %s\n",yytext);
"+"|"-"|"*"|"/"         printf("Operator: %s\n",yytext); 
">"|"<"                 printf("Relational operator: %s\n",yytext); 
"{"[^}\n]*"}"           /* skip one-line comments */
[ \t\n]+                /* skip whitespace */
.                       printf("UNRECOGNIZED: %s\n",yytext); 
%%
main(){ yylex(); }