CDE

Task/Euler-method/D/euler-method.d

@@ -0,0 +1,26 @@
+import std.stdio, std.range;
+
+/**
+Approximates y(t) in y'(t)=f(t,y) with y(a)=y0 and
+t=a..b and the step size h.
+*/
+void euler(F)(in F f, in double y0,
+              in double a, in double b, in double h) {
+    double y = y0;
+    foreach (t; iota(a, b, h)) {
+        writefln("%.3f  %.3f", t, y);
+        y += h * f(t, y);
+    }
+    writeln("done");
+}
+
+void main() {
+    /// Example: Newton's cooling law
+    static newtonCoolingLaw(in double time, in double t) {
+        return -0.07 * (t - 20);
+    }
+
+    euler(&newtonCoolingLaw, 100, 0, 100,  2);
+    euler(&newtonCoolingLaw, 100, 0, 100,  5);
+    euler(&newtonCoolingLaw, 100, 0, 100, 10);
+}