September 2017 Update

Task/Euler-method/Zkl/euler-method.zkl

@@ -0,0 +1,25 @@
+const FMT=" %7.3f";
+
+fcn ivp_euler(f,y,step,end_t){
+   print(" Step %2d: ".fmt(step));
+   foreach t in ([0..end_t,step]){
+      if (t % 10 == 0) print(FMT.fmt(y));
+      y += f(t,y) * step;
+   }
+   println();
+}
+
+fcn analytic{
+   print("    Time: ");
+   foreach t in  ([0..100,10]){ print(" %7g".fmt(t)) }
+   print("\nAnalytic: ");
+   foreach t in ([0..100,10]){ print(FMT.fmt(20.0 + 80.0 * (-0.07 * t).exp())) }
+   println();
+}
+
+fcn cooling(_,temp){ return(-0.07 * (temp - 20)) }
+
+analytic();
+ivp_euler(cooling, 100.0, 2,  100);
+ivp_euler(cooling, 100.0, 5,  100);
+ivp_euler(cooling, 100.0, 10, 100);