Writing a recursive math function

[Teh]

Is my code >.> I tried my best trying to solve but could not get the right answer for my program. I would like know what i did wrong.

Write code to complete RaiseToPower(). Sample output if userBase is 4 and userExponent is 2 is shown below. Note: This example is for practicing recursion; a non-recursive function, or using the built-in function pow(), would be more common.

4^2 = 16

#include <iostream>
using namespace std;

int RaiseToPower(int baseVal, int exponentVal){
   int resultVal = 0;

   if (exponentVal == 0) {
      resultVal = 1;
   }
   else {
      resultVal = baseVal * RaiseToPower(baseVal  , exponentVal - 2 ) ; /*my program 8 */
   }

   return resultVal;
}

int main() {
   int userBase = 0;
   int userExponent = 0;

   userBase = 4;
   userExponent = 2;
   cout << userBase << "^" << userExponent << " = "
        << RaiseToPower(userBase, userExponent) << endl;

   return 0;
}

Testing userBase = 4 and userExponent = 2
Expected output: 4^2 = 16
Your output: 4^2 = 4

 

[squidsk]

There's a critical error on your recursive line. The recursive definition of exponent is given by:

\(\displaystyle {a}^{n} = a * {a}^{?}\)

What's the ? supposed to be and how does that compare with your recursive definition?

 

[Greg]

Here's an interesting piece of code that gets the job done:

int RaiseToPower(int baseVal, int exponentVal) {
   
   if (exponentVal == 0)
      return 1;
   else 
      return (baseVal * RaiseToPower(baseVal, exponentVal - 1));
	
   return 1;
}

Try changing the '1' in the last [m]return[/m] to a '5' and see what happens!

Thanks to FallArk.

 

[squidsk]

Here's an interesting piece of code that gets the job done:

int RaiseToPower(int baseVal, int exponentVal) {
   
   if (exponentVal == 0)
      return 1;
   else 
      return (baseVal * RaiseToPower(baseVal, exponentVal - 1));
	
   return 1;
}

Try changing the '1' in the last [m]return[/m] to a '5' and see what happens!

Thanks to FallArk.

In your code that final return is redundant. You either go into the if or the else block of the conditional and both have a return value so that final return 1; is unreachable code. In the OPs version of the code there are no return statements other than a final return at the end of the function which returns the value set in one of the two branches of the conditional. The OPs problem is still with the recursive call in the else block.

 

[Greg]

Hmm ... I must have made an error somewhere. Ah, well, live and learn. Thanks.

 

[tvman81503]

You were close. The code should read:

resultVal = baseVal * raiseToPower(baseVal, exponentVal - 1 );

Hope this helps.