How to Correctly Invoke a Member Function Pointer in C ?

Member Function Pointer Invocation: Dissecting the Proper Syntax

When working with member function pointers, it's crucial to adhere to the correct syntax to ensure successful execution. Let's delve into a typical issue encountered when attempting to call a member function through a member function pointer and provide the necessary solution.

The erroneous code snippet:

class cat {
public:
   void walk() {
      printf("cat is walking \n");
   }
};

int main(){
   cat bigCat;
   void (cat::*pcat)();
   pcat = &cat::walk;
   bigCat.*pcat();
}

Compilation error: The bigCat.*pcat(); statement generates an error.

Solution:

The key to resolving this issue lies in ensuring the expression bigCat.*pcat() has the appropriate precedence. Operator precedence dictates that unary operators take precedence over binary operators. Thus, parentheses are required to prioritize the function call () over the pointer-to-member binding operation .*.

(bigCat.*pcat)();
^            ^

Enclosing the function call within parentheses ensures its execution first, followed by the member function pointer binding.

Remember:

• Function calls have higher precedence than member function pointer bindings.
• Unary operators take precedence over binary operators.
• Parentheses can be used to control operator precedence and ensure correct execution order.

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