E6_6.c

#include <stdio.h>
#include <math.h>

double calc_clause(double x, int k)
{
    return k == 0 ? 1 : pow(x, k) / (double)fact(k);
}

int fact(int i)
{
    return i == 1 ? 1 : i * fact(i - 1);
}

double myexp(double x)
{
    int k = 0;
    double threshold = pow(10, -6);
    double result = 0.0;

    while (1) {
        double num = calc_clause(x, k);
        if (num < threshold) break;
        result += num;
        k++;
    }

    return result;
}

int main(void)
{
    int i;
    printf("x\tmyexp(x)\n");
    for (i = 1; i < 11; i++) {
        printf("%4.1f\t%13.5f\n", (double)i, myexp((double)i));
    }
    return 0;
}

output.txt

x       myexp(x)
 1.0          2.71828
 2.0          7.38912
 3.0         20.11841
 4.0         57.50654
 5.0        244.87811
 6.0       2110.09358
 7.0      20597.88081
 8.0     164511.80663
 9.0    1053597.01267
10.0    5589274.20360

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