I think I must be brain damaged, because I am having the dumbest problem. I need a power function for a program, and every single one I use is returning zero at all times. I've tried the math.h pow() and two other functions, one recursive and one non-recursive.
The frustrating thing is that this is a tiny, trivial part of what I'm trying to do (find the root of a scalar equation with newton's method), and I can't even seem to get out of the gate.
I've tried compiling with g++ and gcc (need g++ for pow() of course), I've tried changing the value of j, swapping j and cx, changing the types of j and cx, and a whole bunch of other junk.
Any help would be greatly appreciated.
Here's the code, along with the debugging statements that prove to me that I'm getting the wrong answer.
-------------------------------------------
Code:
#include<math.h>
double calcPolyFunctionAtX(double cx);
double power(double px, int y);
double power2( double base, int exp );
/* ********************* */
/* Main */
int main()
{
double f;
/* unimportant stuff */
f = calcPolyFunctionAtX(x);
/* unimportant stuff */
}
/* ********************* */
/* Function for calculating polynomial at x */
double calcPolyFunctionAtX(double cx){
int j;
double answer;
answer = 0;
double z;
z = 0;
for(j=2; j<21; j++){
z = pow(cx, j);
printf("The value of cx is %d \n", cx); /* giving me correct values */
printf("The value of j is %i \n\n", j); /* giving me correct values */
/* all of these are giving me incorrect values */
printf("The value of cx to the jth power by custom non-recursive power function is %d \n", power(cx, j) );
printf("The value of j to the cxth power by custom non-recursive power function is %d \n", power(j, cx) );
printf("The value of cx to the jth power by built-in pow function is %d \n", pow(cx, j) );
printf("The value of j to the cxth power by built-in pow function is %d \n", pow(j, cx) );
printf("The value of cx to the jth power by power2 recursive function is %d \n", power2(cx, j) );
printf("The value of j to the cxth power by power2 recursive function is %d \n", power2(j, cx) ); */
}
/* other junk */
return answer;
}
double power(double px, int y){
double product = 1.0;
int g;
for(g=1; g<=y; g++) {
product *= px;
}
return product;
}
double power2( double base, int exp )
{
int i;
if ( exp < 0 )
return 1.0/power2(base, -exp);
double product = 1.0;
for ( i = 1 ; i <= exp ; i++ )
product *= base;
return product;
}
