/in/foo.c:1:1: error: unknown type name 'def'
    1 | def calculate(num1, num2, operator):
      | ^~~
/in/foo.c: In function 'calculate':
/in/foo.c:1:36: error: expected declaration specifiers before ':' token
    1 | def calculate(num1, num2, operator):
      |                                    ^
/in/foo.c:1:5: warning: type of 'num1' defaults to 'int' [-Wimplicit-int]
    1 | def calculate(num1, num2, operator):
      |     ^~~~~~~~~
/in/foo.c:1:5: warning: type of 'num2' defaults to 'int' [-Wimplicit-int]
/in/foo.c:1:5: warning: type of 'operator' defaults to 'int' [-Wimplicit-int]
/in/foo.c:21: warning: control reaches end of non-void function [-Wreturn-type]