Minor changes to examples

examples/simplest/problem.c

@@ -10,6 +10,8 @@
 #include <stdlib.h>
 
 void heartbeat(struct reb_simulation* r){
+    // This function gets called after every timestep.
+    // Here, we simply print out the current simulation time.
 	printf("%f\n",r->t);
 }
 
@@ -19,14 +21,14 @@ int main(int argc, char* argv[]) {
 	r->heartbeat = heartbeat;
 	r->exact_finish_time = 1; // Finish exactly at tmax in reb_integrate(). Default is already 1.
 
-	struct reb_particle p1 = {0};
+	struct reb_particle p1 = {0}; // always initizialize a struct with this syntax to ensure all variables are set to 0.
 	p1.m = 1.;
-	reb_add(r, p1);
+	reb_add(r, p1);  // reb_add makes a copy of the particle and adds it to the simulation.
 
 	struct reb_particle p2 = {0};
 	p2.x = 1;
 	p2.vy = 1;
-	reb_add(r, p2);
+	reb_add(r, p2); // notice that we didn't set a mass. All parameters default to 0.
 
 	reb_integrate(r,100.);
 }