CODEWITHSUNDEEP
c++
Bartek Maciąg
Bartek Maciąg

Reputation: 29

Wrong function value return

This shoud return result 21.5 but this return 21 where is mistake please help me.

#include <iostream>
#include <string>
#include <conio.h>
using namespace std;

float Funkcja(int a)
{
    static_cast<float>(a);
    a += 1.5;
    return a;
}
void main()
{
    float(*pWskazn)(int);
    pWskazn = &Funkcja;
    cout << (pWskazn)(20);
    getch();
}

Upvotes: 0

Views: 158

Answers (4)

Suvarna Pattayil
Suvarna Pattayil

Reputation: 5239

   static_cast<float>(a);

does not make a a float. It only makes a as a float at that line when it is interpreted.

float b = static_cast<float>(a);
b += 1.5;
return b;

Upvotes: 1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 727037

You are assigning the result back to a, which is int. The result of the cast is not used.

Here is how you can fix the function:

float Funkcja(int a)
{
    return static_cast<float>(a) + 1.5;
}

A cast is an expression, not a declaration. When you do static_cast<float>(a), the compiler calculates the value of the cast, which you can use in further calculations, but the variable itself remains unchanged.

Upvotes: 2

Pete Becker
Pete Becker

Reputation: 76498

static_cast<float>(a) does not change the type of a to float. It converts the value that a holds to a float. As used in the code snippet it then discards the value because it isn't used.

static_cast<float>(a) + 1.5 will do what you want.

Upvotes: 1

olevegard
olevegard

Reputation: 5532

Your cast has no effect, you need to store it in a variable. 

float Funkcja(int a)
{
    float f = static_cast<float>(a);
    f += 1.5;
    return f;
}

Upvotes: 6

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