Function Declaration
A function declaration tells the compiler about the number of parameters, data types of parameters, and returns type of function. Writing parameter names in the function declaration is optional but it is necessary to put them in the definition. Below is an example of function declarations. (parameter names are not present in the below declarations)
Example:
C++
// C++ Program to show function that takes // two integers as parameters and returns // an integer int max( int , int ); // A function that takes an int // pointer and an int variable // as parameters and returns // a pointer of type int int * swap( int *, int ); // A function that takes // a char as parameter and // returns a reference variable char * call( char b); // A function that takes a // char and an int as parameters // and returns an integer int fun( char , int ); |
Functions in C++
A function is a set of statements that takes input, does some specific computation, and produces output. The idea is to put some commonly or repeatedly done tasks together to make a function so that instead of writing the same code again and again for different inputs, we can call this function.
In simple terms, a function is a block of code that runs only when it is called.
Syntax:
Example:
C++
// C++ Program to demonstrate working of a function #include <iostream> using namespace std; // Following function that takes two parameters 'x' and 'y' // as input and returns max of two input numbers int max( int x, int y) { if (x > y) return x; else return y; } // main function that doesn't receive any parameter and // returns integer int main() { int a = 10, b = 20; // Calling above function to find max of 'a' and 'b' int m = max(a, b); cout << "m is " << m; return 0; } |
m is 20
Time complexity: O(1)
Space complexity: O(1)