C++ troubles
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#include <iostream>
#include <cmath> // for abs function
using namespace std;
// ----------------------------------------------
// Function prototypes
double find_root(double (*f)(double ), double a, double b, double tolerance);
double f(double x);
// ---------------------------------------------
// Main
int main(int argc, char** argv)
{double a, b, root;
// Have the user enter the endpoints of the initial interval.
while (1)
{cout << "Enter the endpoints of an interval containing a root: ";
cin >> a >> b;
if (f(a) * f(b) < 0.0)
break;
else
cout << "No sign change on this interval. Try again." << endl;
}
// Find a root and output it.
root = find_root(f, a, b, .0004);
cout << "Root = " << root << endl;
cout << "That's all, folks!" << endl;
return 0;
}
// ------------------------------------------
// Function f follows.
double f (double x)
{
return (x*x*x) - (3.0*x) +1;
}
double find_root(double (*f)(double x), double a, double b, double tolerance)
{
while(abs(a-b) > tolerance)
{
double mid= (a+b)/2;
if(f(a)>=0 && f(mid)<=0 || f(a)<=0 && f(mid)>=0 )
b=mid;
else
a=mid;
}
};
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This code is supposed too find the root of a number but no matter what is typed in the code returns nan assuming the signs are different.
you don't ever return anything from find_root.
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