/in/foo.c:1:1: error: unknown type name 'def'
    1 | def simple_calculator():
      | ^~~
/in/foo.c: In function 'simple_calculator':
/in/foo.c:1:24: error: expected declaration specifiers before ':' token
    1 | def simple_calculator():
      |                        ^
/in/foo.c:20: warning: control reaches end of non-void function [-Wreturn-type]