Adding C to Verlet

Author: Gathros

chapters/computational_physics/verlet.md

@@ -432,3 +432,72 @@ xlabel('Time (s)'); ylabel('Height (m)');
 Submitted by P. Mekhail
 
 ![Verlet LabVIEW](verlet_labview.png)
+
+#### C
+
+```
+#include <stdio.h>
+
+// Simple function for velocity-verlet
+void verlet(double pos, double acc, double dt){
+
+    // Note that we are using a temp variable for the previous position
+    double prev_pos, temp_pos, time;
+    prev_pos = pos;
+    time = 0;
+
+    while (pos > 0){
+        time += dt;
+        temp_pos = pos;
+        pos = pos*2 - prev_pos + acc * dt * dt;
+        prev_pos = temp_pos;
+    }
+
+   printf("%f\n", time);
+
+}
+
+// Simple function for stormer-verlet
+void stormer_verlet(double pos, double acc, double dt){
+
+    double prev_pos, temp_pos, time, vel;
+    prev_pos = pos;
+    vel = 0;
+    time = 0;
+    while (pos > 0){
+        time += dt;
+        temp_pos = pos;
+        pos = pos*2 - prev_pos + acc * dt * dt;
+        prev_pos = temp_pos;
+
+        // The acceleration is constant, so the velocity is straightforward
+        vel += acc*dt;
+    }
+
+   printf("%f\n", time);
+
+}
+
+// Simple function for velocity-verlet
+void velocity_verlet(double pos, double acc, double dt){
+
+    double time, vel;
+    vel = 0;
+    time = 0;
+    while (pos > 0){
+        time += dt;
+        pos += vel*dt + 0.5*acc * dt * dt;
+        vel += acc*dt;
+    }
+
+   printf("%f\n", time);
+
+}
+
+int main(){
+    verlet(5.0, -10, 0.01);
+    stormer_verlet(5.0, -10, 0.01);
+    velocity_verlet(5.0, -10, 0.01);
+
+}
+```