September 2017 Update

Task/Euler-method/BBC-BASIC/euler-method.bbc

@@ -1,15 +0,0 @@
-      PROCeuler("-0.07*(y-20)", 100, 0, 100, 2)
-      PROCeuler("-0.07*(y-20)", 100, 0, 100, 5)
-      PROCeuler("-0.07*(y-20)", 100, 0, 100, 10)
-      END
-
-      DEF PROCeuler(df$, y, a, b, s)
-      LOCAL t, @%
-      @% = &2030A
-      t = a
-      WHILE t <= b
-        PRINT t, y
-        y += s * EVAL(df$)
-        t += s
-      ENDWHILE
-      ENDPROC

Task/Euler-method/Futhark/euler-method.futhark

@@ -1,15 +1,17 @@
+import "futlib/math"
+
 fun analytic(t0: f64) (time: f64): f64 =
-  20.0 + (t0 - 20.0) * exp64(-0.07*time)
+  20.0 + (t0 - 20.0) * f64.exp(-0.07*time)
 
 fun cooling(_time: f64) (temperature: f64): f64 =
   -0.07 * (temperature-20.0)
 
 fun main(t0: f64) (a: f64) (b: f64) (h: f64): []f64 =
-  let steps = int((b-a)/h)
+  let steps = i32((b-a)/h)
   let temps = replicate steps 0.0
   loop ((t,temps)=(t0,temps)) = for i < steps do
     let x = a + f64(i) * h
-    let temps[i] = abs(t-analytic t0 x)
+    let temps[i] = f64.abs(t-analytic t0 x)
     in (t + h * cooling x t,
         temps)
  in temps

Task/Euler-method/Kotlin/euler-method.kotlin

@@ -0,0 +1,32 @@
+// version 1.1.2
+
+typealias Deriv = (Double) -> Double  // only one parameter needed here
+
+const val FMT = " %7.3f"
+
+fun euler(f: Deriv, y: Double, step: Int, end: Int) {
+    var yy = y
+    print(" Step %2d: ".format(step))
+    for (t in 0..end step step) {
+        if (t % 10 == 0) print(FMT.format(yy))
+        yy += step * f(yy)
+    }
+    println()
+}
+
+fun analytic() {
+    print("    Time: ")
+    for (t in 0..100 step 10) print(" %7d".format(t))
+    print("\nAnalytic: ")
+    for (t in 0..100 step 10)
+        print(FMT.format(20.0 + 80.0 * Math.exp(-0.07 * t)))
+    println()
+}
+
+fun cooling(temp: Double) = -0.07 * (temp - 20.0)
+
+fun main(args: Array<String>) {
+    analytic()
+    for (i in listOf(2, 5, 10))
+        euler(::cooling, 100.0, i, 100)
+}

Task/Euler-method/Run-BASIC/euler-method.run

@@ -1,14 +0,0 @@
-x = euler(-0.07,-20, 100, 0, 100, 2)
-x = euler-0.07,-20, 100, 0, 100, 5)
-x = euler(-0.07,-20, 100, 0, 100, 10)
-end
-
-FUNCTION euler(da,db, y, a, b, s)
-print "===== da:";da;" db:";db;" y:";y;" a:";a;" b:";b;" s:";s;" ==================="
-t = a
-WHILE t <= b
-   PRINT t;chr$(9);y
-   y = y + s * (da * (y + db))
-   t = t + s
-WEND
-END FUNCTION

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);