Worked on ass4.

modsim/ass2/q4.c

@@ -3,10 +3,35 @@
 #include <math.h>
 #include "func_ptr.h"
 
-double newton(func_ptr f, func_ptr df, double x_start) {
+#define EPSILON 1e-11
 
+double bisec_limited(func_ptr f, double left, double right, int max_steps) {
+    int i;
+    double mid;
 
-    return 0;
+    for( i = 0; fabs(right - left) > 2 * EPSILON && i < max_steps; i++ ) {
+        mid = (right + left) / 2;
+
+        if( f(left) * f(mid) < 0 )
+            right = mid;
+        else if( f(right) * f(mid) < 0 )
+            left = mid;
+        else
+            break;
+    }
+
+    return mid;
+}
+
+double newton(func_ptr f, func_ptr df, double x_start, int *steps) {
+    double x = x_start, last_x = x - 1;
+
+    for( *steps = 0; x != last_x; (*steps)++ ) {
+        last_x = x;
+        x -= f(x) / df(x);
+    }
+
+    return x;
 }
 
 double f1(double x) {
@@ -30,11 +55,13 @@ double f3(double x) {
 }
 
 double df3(double x) {
-    return (x * x + 1) + 2 * x  * (x - 4);
+    return (x * x + 1) + 2 * x * (x - 4);
 }
 
 int main(void) {
-    printf("f1: %.11f\n", newton(&f1, &df1, 1));
+    int steps;
+
+    printf("f1: %.11f (%d steps)\n", newton(&f2, &df2, -100, &steps), steps);
 
     return 0;
 }