31 lines
941 B
C
31 lines
941 B
C
#include <math.h>
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#define TOLERANCE 0.0000001
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/*
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A C adaptation of Dr. Ching-Kuang Shene's FORTRAN version
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from https://pages.mtu.edu/~shene/COURSES/cs201/NOTES/chap04/exp.html
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I was stuck on how to actually implement the Taylor series without it
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getting far too big for even a long double, and I'm not sure I ever would
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have thought to just break it out recursively like this. Instead of each
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term being x^n/n!, where we have to figure out both x^n and n!, both of which
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could be massive, we instead say that it's (x/n+1)*(nth term), with a base
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case (1st term) of x/1! = x. Pretty clever, really.
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Also, really glad I know how to at least read a basic FORTRAN program. This
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probably would have been a little more annoying if I didn't.
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-Kat
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*/
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double exp(double x) {
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double term = x;
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double sum = 1.0;
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for(int i = 1; fabs(term) > TOLERANCE; i++) {
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sum += term;
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term *= (x / i);
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}
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return sum;
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} |