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void (*ptr)() defines a function pointer. It says that ptr is a pointer to a function. But that function must have a void return type, and take an arbitrary number of parameters (that's what the em...
Answer
#4: Post edited
by
Martin Bonner
·
2022-03-31T11:50:30Z (over 2 years ago)
This is C not C++, empty parens imply an arbitrary number of arguments, not "no arguments".
`void (*ptr)()` defines a function pointer. It says that `ptr` is a pointer to a function. But that function must have a `void` return type, and take no parameters (that's what the empty parentheses defines).Then, `ptr = PrintHello` assigns the `PrintHello` function to the `ptr` pointer (and it works because `PrintHello` matches the signature: it has a `void` return type and takes no parameters). So, now `ptr` is pointing to `PrintHello`.- Finally, `ptr()` is calling the function that `ptr` points to (in this case, `PrintHello`). It has the same effect as calling `PrintHello()`, and the parentheses are needed because it's a function call. But the function takes no parameters, thus the empty parentheses.
- `void (*ptr)()` defines a function pointer. It says that `ptr` is a pointer to a function. But that function must have a `void` return type, and take an arbitrary number of parameters (that's what the empty parentheses defines).
- Then, `ptr = PrintHello` assigns the `PrintHello` function to the `ptr` pointer (and it works because `PrintHello` matches the signature: it has a `void` return type). So, now `ptr` is pointing to `PrintHello`.
- Finally, `ptr()` is calling the function that `ptr` points to (in this case, `PrintHello`). It has the same effect as calling `PrintHello()`, and the parentheses are needed because it's a function call. But the function takes no parameters, thus the empty parentheses.
#3: Post edited
by
hkotsubo
·
2021-12-05T15:02:48Z (about 3 years ago)
- `void (*ptr)()` defines a function pointer. It says that `ptr` is a pointer to a function. But that function must have a `void` return type, and take no parameters (that's what the empty parentheses defines).
Then, `ptr = PrintHello` assigns the `PrintHello` function to the `ptr` pointer (because `PrintHello` matches the signature: it has a `void` return type and takes no parameters). So, now `ptr` is pointing to `PrintHello`.- Finally, `ptr()` is calling the function that `ptr` points to (in this case, `PrintHello`). It has the same effect as calling `PrintHello()`, and the parentheses are needed because it's a function call. But the function takes no parameters, thus the empty parentheses.
- `void (*ptr)()` defines a function pointer. It says that `ptr` is a pointer to a function. But that function must have a `void` return type, and take no parameters (that's what the empty parentheses defines).
- Then, `ptr = PrintHello` assigns the `PrintHello` function to the `ptr` pointer (and it works because `PrintHello` matches the signature: it has a `void` return type and takes no parameters). So, now `ptr` is pointing to `PrintHello`.
- Finally, `ptr()` is calling the function that `ptr` points to (in this case, `PrintHello`). It has the same effect as calling `PrintHello()`, and the parentheses are needed because it's a function call. But the function takes no parameters, thus the empty parentheses.
#2: Post edited
by
hkotsubo
·
2021-12-05T15:00:59Z (about 3 years ago)
- `void (*ptr)()` defines a function pointer. It says that `ptr` is a pointer to a function. But that function must have a `void` return type, and take no parameters (that's what the empty parentheses defines).
- Then, `ptr = PrintHello` assigns the `PrintHello` function to the `ptr` pointer (because `PrintHello` matches the signature: it has a `void` return type and takes no parameters). So, now `ptr` is pointing to `PrintHello`.
Finally, `ptr()` is calling the function that `ptr` points to (in this case, `PrintHello`).
- `void (*ptr)()` defines a function pointer. It says that `ptr` is a pointer to a function. But that function must have a `void` return type, and take no parameters (that's what the empty parentheses defines).
- Then, `ptr = PrintHello` assigns the `PrintHello` function to the `ptr` pointer (because `PrintHello` matches the signature: it has a `void` return type and takes no parameters). So, now `ptr` is pointing to `PrintHello`.
- Finally, `ptr()` is calling the function that `ptr` points to (in this case, `PrintHello`). It has the same effect as calling `PrintHello()`, and the parentheses are needed because it's a function call. But the function takes no parameters, thus the empty parentheses.
#1: Initial revision
by
hkotsubo
·
2021-12-05T14:59:05Z (about 3 years ago)
`void (*ptr)()` defines a function pointer. It says that `ptr` is a pointer to a function. But that function must have a `void` return type, and take no parameters (that's what the empty parentheses defines). Then, `ptr = PrintHello` assigns the `PrintHello` function to the `ptr` pointer (because `PrintHello` matches the signature: it has a `void` return type and takes no parameters). So, now `ptr` is pointing to `PrintHello`. Finally, `ptr()` is calling the function that `ptr` points to (in this case, `PrintHello`).