Data commit

Task/Continued-fraction/C/continued-fraction.c

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+/* calculate approximations for continued fractions */
+#include <stdio.h>
+
+/* kind of function that returns a series of coefficients */
+typedef double (*coeff_func)(unsigned n);
+
+/* calculates the specified number of expansions of the continued fraction
+ * described by the coefficient series f_a and f_b */
+double calc(coeff_func f_a, coeff_func f_b, unsigned expansions)
+{
+	double a, b, r;
+	a = b = r = 0.0;
+
+	unsigned i;
+	for (i = expansions; i > 0; i--) {
+		a = f_a(i);
+		b = f_b(i);
+		r = b / (a + r);
+	}
+	a = f_a(0);
+
+	return a + r;
+}
+
+/* series for sqrt(2) */
+double sqrt2_a(unsigned n)
+{
+	return n ? 2.0 : 1.0;
+}
+
+double sqrt2_b(unsigned n)
+{
+	return 1.0;
+}
+
+/* series for the napier constant */
+double napier_a(unsigned n)
+{
+	return n ? n : 2.0;
+}
+
+double napier_b(unsigned n)
+{
+	return n > 1.0 ? n - 1.0 : 1.0;
+}
+
+/* series for pi */
+double pi_a(unsigned n)
+{
+	return n ? 6.0 : 3.0;
+}
+
+double pi_b(unsigned n)
+{
+	double c = 2.0 * n - 1.0;
+
+	return c * c;
+}
+
+int main(void)
+{
+	double sqrt2, napier, pi;
+
+	sqrt2  = calc(sqrt2_a,  sqrt2_b,  1000);
+	napier = calc(napier_a, napier_b, 1000);
+	pi     = calc(pi_a,     pi_b,     1000);
+
+	printf("%12.10g\n%12.10g\n%12.10g\n", sqrt2, napier, pi);
+
+	return 0;
+}