Calculate the exponential by recursion

Latest update on December 7, 2010 at 05:16 AM by aakai1056 .

Calculate the exponential by recursion

Issue

Please, I would like to know the error (s) that exists in this algorithm. For information: this algorithm is to compute the exponential method by recursion.

#include #include #include int factoriel(int n, int i, int fact) { if(i=n+1) { fact=1; return fact; } else { fact = fact*i; i++; factoriel(n,i,fact); } } float puissance(int n, int i, float x, float p) { if(i=n+1) { p=1; return p; } else { p=p*x; i++; puissance(n,i,x,p); } } int main() { const float EPS=0.0001; int i, n, fact; float x,p,s,T; printf("Donner x: "); scanf("%f", &x); n=0; T=1; s=0; fact=1; p=1; while(floor(T) > EPS) { T=puissance(n,1,x,p)/factoriel(n, 1, fact); s=s+T; n=n+1; } printf("Exp(%f) = %f

", x, s); }

Solution

Several errors.

I pass over the absurdity of using recursion to calculate the factorial and power, I suppose you requested.

First, detailed syntax ultra-classic: the test is ==, not =. In your two functions should be if (i == n +1)

Worse, in the else test both functions, there is no return. So your function returns nothing, it may take a random value. I guess the idea was to have the first return factorial (n, i, fact);

But even with this correction factor and Thy power will not work. You make fine calculations, then returned to the stage n +1, you can force the result to 1!

Finally, in your hand, you have reinitialize p and fact on each loop.

In my opinion it is better to write the factorial function and power to work by decreasing values (from n to 1) rather than increasing from 1 to n +1. Function only requires one parameter, it is much simpler (no i, Fact, or p)

Note

Solve by le père