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  1. %option noyywrap
  2.  
  3. %%
  4.  
  5. [0-9][a-zA-Z0-9_]+        { printf("Invalid Identifier: %s (cannot start with digit)\n", yytext); }
  6.  
  7. [@#$%^&*\-+][a-zA-Z0-9_]*  { printf("Invalid Identifier: %s (cannot start with special character)\n", yytext); }
  8.  
  9. [ \t\n]+    ; 
  10.  
  11. %%
  12.  
  13. int main() {
  14.     printf("Enter input:\n");
  15.     yylex();
  16.     return 0;
  17. }
Success #stdin #stdout #stderr 0.03s 6940KB
comments (?)
stdin 
Standard input is empty
stdout 
Standard output is empty
stderr 
ERROR: /home/h8oLw5/prog:17:0: Syntax error: Unexpected end of file
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/Rm6c5x
language:
Prolog (swi 7.6.4)
created:
7 hours ago
visibility:
public

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