function that returns 2 raised to the power of its argument

[kyleg033]

Hi, Im new to the forums, and very new to C++. I have an assignment for my entry level c++ class that I am having trouble with. What I have to do is written in the title. This is what I have, let me know if you would change anything or if this would even work. The argument must be greater than or equal to zero.


int power (int two, int exponent)
{
int zero = 1;

if (exponent == 1)
return base;

else if (exponent == 0)
return zero;

else

return two * power(two, exponent - 1);
}

[kyleg033]

int power (int two, int exponent)
{
int zero = 1;
int two = 2;

if (exponent == 1)
return two;

else if (exponent == 0)
return zero;

else
return two * power(two, exponent - 1);
}

[Duthomhas]

Don't make magic numbers. Use the number itself.

int two_to_the_power_of( int exponent )
{
  if (exponent == 0)
    return 1;

  if (exponent == 1)
    return 2;

  return 2 * two_to_the_power_of( exponent - 1 );
}

The best way to know if it works is to test it.

#include <iostream>

...

int main()
{
  for (int n = 0; n < 10; n++)
    cout << "2 to the " << n << " is " << two_to_the_power_of( n ) << endl;
  return 0;
}

By the way, what happens if the user says two_to_the_power_of( -3 );?

Hope this helps.

[helios]

I like how 'two' contains 2, but 'zero' contains 1.

[moorecm]

Allow me to comment on the code that you have so far:

1 2 3 4 5 6

int power (int two, int exponent) { int zero = 1; int two = 2; //...

<- The parameter 'two' is either not necessary or named very, very poorly. <- This is humorous, at least. <- This local variable 'two' hides the function parameter 'two'. The rest of the logic just reads silly because of the variable names. :P

[jLNv0pDG]

@Duoas: I know it's a different way of doing the same thing, but aren't for loops more efficient than recursive function calls?

int two_to_the_power_of( int exponent )
{
	int answer = 1;

	for (int i = 0; i < exponent; ++i) 
		answer *= 2;
		
	return answer;
}

[kyleg033]

Thanks alot for the feedback guys, sorry I know I'm not very good at writing code but you have to start somewhere!

[kyleg033]

Anybody have any opinion on a good strategy to learning C++??? Any good books??? How did you guys do it?

[Duthomhas]

@farcear
Yes, they are, but I only made two changes to the OP's code, which was recursive.

@kyleg033
Just do it, and learn everything you can about what it is you are currently doing.

I started out writing simple utilities (menu systems and the like) and games (breakout clone, hangman, Ladder clone, etc) and utilities to help (pixel editor, dungeon map editor, etc).

[kyleg033]

Duoas,

Thanks alot you are a huge help!

[jRaskell]

Short and sweet (or perhaps not so sweet, but definitely short)

int two_pow(int exp){
	return 1 << exp;
}

[Duthomhas]

Shhh! That's how I would have done it.