CDE

Task/Euler-method/ALGOL-68/euler-method.alg

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+#
+Approximates y(t) in y'(t)=f(t,y) with y(a)=y0 and
+t=a..b and the step size h.
+#
+PROC euler = (PROC(REAL,REAL)REAL f, REAL y0, a, b, h)REAL: (
+    REAL y := y0,
+         t := a;
+    WHILE t < b DO
+      printf(($g(-6,3)": "g(-7,3)l$, t, y));
+      y +:= h * f(t, y);
+      t +:= h
+    OD;
+    printf($"done"l$);
+    y
+);
+
+# Example: Newton's cooling law #
+PROC newton cooling law = (REAL time, t)REAL: (
+    -0.07 * (t - 20)
+);
+
+main: (
+   euler(newton cooling law, 100, 0, 100,  10)
+)