Data update

Task/Euler-method/Rebol/euler-method.rebol

@@ -0,0 +1,34 @@
+Rebol [
+    title: "Rosetta code: Euler method"
+    file:  %Euler_method.r3
+    url:   https://rosettacode.org/wiki/Euler_method
+]
+
+euler: func[
+    "Euler's method for Newton's cooling law, with formatted comparison"
+    step      [integer!] "time step in seconds"
+    precision [decimal!] "rounding granularity for printed numbers"
+][
+    print ["^/STEP:" step]
+    print "Time  Euler      Analytic"
+    print "-------------------------"
+
+    ;; Initialize:
+    ;; b: upper time bound (seconds) — here we reuse the initial temperature value 100
+    ;; y: the current Euler-approximated temperature; initial condition T(0) = 100
+    b: y: 100
+    for time 0 b step [
+        printf [-3 " | " 9 "| "] reduce [
+            time
+            round/to y precision
+            round/to (20 + (80 * exp (-0.07 * time))) precision
+        ]
+        ;; Euler step update:
+        ;; This applies the discrete forward Euler update using the ODE's RHS
+        y: y + (step * (-0.07 * (y - 20)))
+    ]
+]
+;; Run three experiments with different step sizes
+euler 2  0.0001
+euler 5  0.0001
+euler 10 0.0001