tasks a-s

Task/Numerical-integration/C/numerical-integration-1.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+double int_leftrect(double from, double to, double n, double (*func)())
+{
+   double h = (to-from)/n;
+   double sum = 0.0, x;
+   for(x=from; x <= (to-h); x += h)
+      sum += func(x);
+   return h*sum;
+}
+
+double int_rightrect(double from, double to, double n, double (*func)())
+{
+   double h = (to-from)/n;
+   double sum = 0.0, x;
+   for(x=from; x <= (to-h); x += h)
+     sum += func(x+h);
+   return h*sum;
+}
+
+double int_midrect(double from, double to, double n, double (*func)())
+{
+   double h = (to-from)/n;
+   double sum = 0.0, x;
+   for(x=from; x <= (to-h); x += h)
+     sum += func(x+h/2.0);
+   return h*sum;
+}
+
+double int_trapezium(double from, double to, double n, double (*func)())
+{
+   double h = (to - from) / n;
+   double sum = func(from) + func(to);
+   int i;
+   for(i = 1;i < n;i++)
+       sum += 2.0*func(from + i * h);
+   return  h * sum / 2.0;
+}
+
+double int_simpson(double from, double to, double n, double (*func)())
+{
+   double h = (to - from) / n;
+   double sum1 = 0.0;
+   double sum2 = 0.0;
+   int i;
+
+   double x;
+
+   for(i = 0;i < n;i++)
+      sum1 += func(from + h * i + h / 2.0);
+
+   for(i = 1;i < n;i++)
+      sum2 += func(from + h * i);
+
+   return h / 6.0 * (func(from) + func(to) + 4.0 * sum1 + 2.0 * sum2);
+}