What's the effect of "int a(); " in C++?

Question

What's the effect of int a(); in C++?

Is it equivalent to int a or int a(0)?

And how about char c() and double d()?

Answer 1

What's the effect of int a(); in C++?

That declares a function, with no parameters, that returns an integer.

Is it equivalent to int a or int a(0)?

No. Each of these declares a variable of integer type; the second also initialises it with the value zero.

And how about char c() and double d()? Thanks.

These also declare functions, with different return types.

Answer 2

int a(); is a function declaration.

int a is declaring a to be of type int.

int a(0) is declaring a to be of type int and initialising it to 0.

char c() and double d() are function declarations also returning char and double respectively.

All the function declarations should be terminated by a ;.

Answer 3

Neither, it declares a function.