Initial data commit

Task/Forward-difference/C/forward-difference-1.c

@@ -0,0 +1,39 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+double* fwd_diff(double* x, unsigned int len, unsigned int order)
+{
+	unsigned int i, j;
+	double* y;
+
+	/* handle two special cases */
+	if (order >= len) return 0;
+
+	y = malloc(sizeof(double) * len);
+	if (!order) {
+		memcpy(y, x, sizeof(double) * len);
+		return y;
+	}
+
+	/* first order diff goes from x->y, later ones go from y->y */
+	for (j = 0; j < order; j++, x = y)
+		for (i = 0, len--; i < len; i++)
+			y[i] = x[i + 1] - x[i];
+
+	y = realloc(y, sizeof(double) * len);
+	return y;
+}
+
+int main(void)
+{
+	double *y, x[] = {90, 47, 58, 29, 22, 32, 55, 5, 55, 73};
+	int i, len = sizeof(x) / sizeof(x[0]);
+
+	y = fwd_diff(x, len, 1);
+	for (i = 0; i < len - 1; i++)
+		printf("%g ", y[i]);
+	putchar('\n');
+
+	return 0;
+}