Exponents don't work! 2

[fafasdgsadgas]

I have recently started learning about C++ and got Visual C++ 6 Standard Edition, I tried to make a program that would ask for a number and then print the values of that number to the power of 0-20, unfortunately it won't seem to do the equation correctly. I tried setting up a function for the equation but it still won't work. I did include the cstdlib and cmath headers and even tried stdlib.h and math.h with no avail. I also have conio.h, if that helps at all. Is it a bug in Visual Studio or my error? I'll send the source if requested.

 

[Sebastiani]

Well, let's see what you've tried. Generally a simple for() loop is sufficient.

 

[Bones3]

What is(are) the error message(s) you are getting? Let them see the source for the equation function if you are convinced the error is there.

-Bones

 

[fafasdgsadgas]

#include <conio.h>
#include <iostream>
#include <math.h>
#include <cmath>
#include <cstdlib>
using namespace std;

int pow(int first, int second);

int main()
{
int num=0;
int power=0;
int count=0;
cout<<&quot;Created by Martin Castner&quot;<<endl;
cout<<&quot;It will ask for a number and then show the value of the number to the power of 0 through 20.&quot;<<endl;
cout<<&quot;Please enter the base number:&quot;<<endl;
cin>>num;
for(int count=0;count<21;count++)
{
power=num^count;
cout<<num<<&quot; to the power of &quot;<<expon<<&quot; is equal to &quot;<<power<<&quot;.&quot;<<endl;

}
cout<<&quot;Press any key to quit...&quot;<<endl;
getch();
return 0;
}



That is my source, fairly small. There are no errors but try it out and see if it works for you. If I enter 1 as the base it will do:
1^0=1
1^1=0 (really doing 1-1)
1^2=3 (2+1)
1^3=2 (3-1)
1^4=5 (4+1)
etc...

 

[Clairvoyant1332]

There is no power operator in C. The ^ operator you're using is for the &quot;bitwise exclusive or&quot; operation. The results you're getting reflect those results.

There is, however, a pow() function that does this operation.

Dennis

 

[fafasdgsadgas]

what is the pow() function?

 

[Clairvoyant1332]

The definition looks like this:

double pow(double x, double y);

It returns x to the power of y. You'll need to #include math.h.

 

[Sebastiani]

It's in math.h (and cmath).

 

[fafasdgsadgas]

Didn't help! This is what I put:

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


int main()
{
double num=0;
double power=0;
double count=0;
cout<<&quot;Programmed by Martin Castner&quot;<<endl;
cout<<&quot;It will ask for a number and then show the value of the number to the power of 0 through 20.&quot;<<endl;
cout<<&quot;Please enter the base number:&quot;<<endl;
cin>>num;

for(int count=0;count<21;count++)
{
power=pow(double num, double count);
cout<<num<<&quot; to the power of &quot;<<count<<&quot; is equal to &quot;<<power<<&quot;.&quot;<<endl;

}
cout<<&quot;Press any key to quit...&quot;<<endl;
getch();
return 0;
}

What's wrong, I put a function prototype at the beginning too but it didn't work either. I get the same results as last time.

 

[uolj]

If you fix the compile errors this should work fine. The compile errors you are getting should point you to what to fix, but here are a few more hints:[ol][li]You declared count twice, once as a double and once inside the for loop as an int. Just declare it once as a double.[/li][li]When you are calling a function, you aren't supposed to specify the type of the parameter that you are passing in. So when you call pow you don't need to put 'double' before 'num' and 'count'.[/li][li]Just a suggestion: use all of the new/correct runtime library headers instead of mixing and matching (e.g. cmath, cstdlib, and iostream).[/li][/ol]Once I fixed the compile errors it seemed to work for me.

 

[fafasdgsadgas]

I gotta update my software! I never got any compile errors or anything and it still won't work. Let me get all the updates and check back with you.

 

[fafasdgsadgas]

It works! Just installed SP 5 for Visual C++ and everything worked without needing to change the program at all, I guess it was my compiler!

 

[Sebastiani]

No, you didn't listen to uolj's response, it's not a compiler error, it's a keyboard error ( ie: what you typed. ).

So again:

>> int count=0;

...then

>> for(int count=0;count<21;count++)

...declared again!


Luckily, there is no side effect in this case, but still, an error's an error.


>> power=pow(double num, double count);

That of course should be:

>> power=pow(num, count);


Now for a couple of nitpicks.

>> cin>>num;

cin should *always* be followed up with a:

>> if(cin.good()) // safe to proceed

Finally, cin.get() can be used instead of getch(), meaning you wouldn't have to include the non-portable <conio.h>.