Issues with function output using if/else if

Question

I am (new to c++) trying to create a power function manually and came across the issue where if the power inputted is negative, the result is always being printed out as 0. I suspect that one of the variables might not be declared properly, can you help please

#include <iostream>

using namespace std;

int power;
float result = 1, base;

int firs();
void pow(int base, int power);

int main()
{
    firs();
    pow(base, power);

    return 0;
}

int firs()
{
    cout << "Enter a base input: ";
    cin >> base;

    cout << "Enter a power input: ";
    cin >> power;

    return base, power;
}

void pow(int base, int power)
{
    cout << "With a given base of " << base << " and a given power of " << power << endl;

    if (power > 0)
    {
        for (int i = 0; i < power; i++)
        {
            result = result*base;
        }

    cout << "The final answer is: " << result;

    }
    else if (power < 0)
    {
        for (int i = 0; i > power; i--)
        {
            result = result*(1/base);
        }

    cout << "The final answer is: " << result;
    }
    else
    {
        cout << "The final answer is: " << 1;
    }
}

@Tony Yes, comma operator (`,`) executes all statements from left to right, and returns the rightmost one. So `return base, power;` is exactly the same as `return power;` — Yksisarvinen, May 30 '19 at 22:05
In C/C++ you can only return one value from a function. Or give back a struct or change values by references — B. Go, May 30 '19 at 22:07
@Tony [more info here](https://en.cppreference.com/w/cpp/language/operator_other#Built-in_comma_operator) — Not a real meerkat, May 30 '19 at 22:08
It takes me awhile to see that `base` definition in `pow` function is shadowing `base` definition at global scope. The former is `int` and the later is `float` — Amadeus, May 30 '19 at 22:14

Xiaoyi Cao · Answer 1 · 2019-05-30T22:10:53.670

The problem lies in the following code section:

    else if (power < 0)
    {
        for (int i = 0; i > power; i--)
        {
            result = result*(1/base);
        }
    }

When (1/base) is calculated, because both 1 and base are int, the result will also be casted into int, which is 0 (if base is greater than 1). You can avoid this by either defining base as float, using 1.0 instead of 1, or using explicit type casting:

    else if (power < 0)
    {
        for (int i = 0; i > power; i--)
        {
            result = result*(1/(float) base);
        }
    }

Also, return base, power only returns power.

Ah, just as I expected. Thanks. – Bo Jackson May 30 '19 at 22:11 — Bo Jackson, May 30 '19 at 22:11

score 0 · Answer 2 · answered May 30 '19 at 22:10

0

Just change this line

        result = result*(1/base);

to

        result = result*(1.0/base);

And you will get the correct result.

answered May 30 '19 at 22:10

Tony

632
1
4
18

Issues with function output using if/else if

2 Answers2