CODEWITHSUNDEEP
c++while-loop
Stitch
Stitch

Reputation: 31

How to do a pow function inside of while? C++

Here is the problem I must do(Just for context): Write a program that will input 2 integers from the user, will then calculate the first to the power of the second and then output the result. The Input, calculation and output should be in three separate subprograms/functions. You must calculate the exponentiation using a WHILE loop and multiplying the first number, the required number of times. For this homework only, you are allowed to use global variables to move information between functions. Here is my code:

#include <iostream>
#include <cmath>
using namespace std;

double a, b, ans;


int main()
{
    cout << "Please enter two whole numbers: ";
    cin >> a >> b;
    cout << conclusion() << calc();

    system("pause");
    return 0;
}

int calc()
{
    double ans = pow(a, b);
    return 0;
}

int conclusion()
{
    cout << a << " To the power of " << b
         << " is " << ans;
    return 0;
}

So here's what I'm having an issue with, I do online classes. The dude is like, "here's a problem, figure it out and just do it." Which is fine I guess, but when things like this come up its hard to find certain tutorials and questions. Anyway, I got my BASE code down. Now I need a while loop, and have no idea what this means: calculate the exponentiation using a WHILE loop and multiplying the first number, the required number of times. I figured I could just do a while and do 

double ans = pow(a, b);

But that's not the case apparently. That's what my chapter taught me, but not with a while and all this extra stuff you need to do for this. I asked a classmate, she said she had a really difficult time as well, and her example to me was: 

int a = 0;

int b =  0;

int c = 1;

cin >> a;

cin >> b;

int powerOp(int a, int b, int c)
{

while (b > 0)
          {
               c = c * a;

               b--;
          }
               cout  <<  c;
               return c;
}

I have been working almost all day and can't figure this out. I don't understand why we need to factorize and set the int = 1. I thought it could simply be

double ans = pow(a, b); //a and b being the 2 numbers the user inputs

Upvotes: 0

Views: 1380

Answers (2)

Stitch
Stitch

Reputation: 31

Okay so I'm pretty sure I found the answer. Result is the variable for ans

int calc() //function for calculation
{

    //Still not sure how I did this one, after hours of playing around with it
    while (b > 0) //This code is adding a 0 in the result. I can't figure it out
    {
        result = result * a;
        b--;
    }

    return (result);
}

This is just a simple solution, as it wants to add a 0 in the end result.

Upvotes: 0

Picnic8
Picnic8

Reputation: 373

Its pretty simple, lets say you have 2^3. You and I both agree that it is the same as doing 2x2x2. You mutiplied you first number A by itself B (your second number) times. Now for your loop, what you want have your second number server as your counter AND loop exit condition. Something like this

double YourPowerFunction(int a, int b)
{
    int counter = 0;
    double result = 1;

    while (counter < b)
    {
        counter++:
        result = result * a;
    }
    return result;
}

Upvotes: 1

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