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  1. %{
  2. #include <stdio.h>
  3. #include <ctype.h>
  4. %}
  5.  
  6. %%
  7. [a-z]   { printf("%c", toupper(yytext[0])); }
  8. [A-Z]   { printf("%c", tolower(yytext[0])); }
  9. .|\n    { printf("%c", yytext[0]); }
  10. %%
  11. int yywrap()
  12. {
  13.     return 1;
  14. }
  15. int main()
  16. {
  17.     printf("Enter a string: ");
  18.     yylex();
  19.     return 0;
  20. }
  21.  
Success #stdin #stdout #stderr 0.02s 6884KB
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stdin
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abc
stdout
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Standard output is empty
stderr
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ERROR: /home/uDO7dR/prog:20:1: Syntax error: Unexpected end of file
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/O61yIZ
language:
Prolog (swi 7.6.4)
created:
5 hours ago
visibility:
public

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