Runge-Kutta method: Difference between revisions

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 =={{header|Perl 6}}==
+{{trans|Perl}}
-<lang perl6>sub runge-kutta (&yp, $t is copy, $y is copy, \δt) {
-    gather loop {
+<lang perl6>sub runge-kutta(&yp, \δt) {
-	FIRST take $y;
-	my @δy = δt * yp $t, $y;
+    return -> \t, \y {
-	@δy.push: δt * yp $t + δt / 2, $y + @δy[0] / 2;
+	my @dy =  δt * yp( t       , y );
-	@δy.push: δt * yp $t + δt / 2, $y + @δy[1] / 2;
+	push @dy, δt * yp( t + δt/2, y + @dy[0]/2 );
-	@δy.push: δt * yp $t += δt, $y + @δy[2];
+	push @dy, δt * yp( t + δt/2, y + @dy[1]/2 );
-	take $y += 6 R/ [+] <1 2 2 1> Z* @δy ;
+	push @dy, δt * yp( t + δt  , y + @dy[2] );
+	t + δt, y + 6 R/ [+] <1 2 2 1> Z* @dy;
     }
 }
+my &RK = runge-kutta { $^t * sqrt($^y) }, .1;
-constant δt = 0.1;
-constant n = 10.0;
+loop ( my ($t, $y) = (0, 1); $t <= 10; ($t, $y) = RK($t, $y)) {
-constant @t = 0, δt ... n;
-my @y := runge-kutta -> $t, $y { $t * sqrt $y }, @t[0], 1, δt;
+    printf "y(%2.0f) = %12f ± %e\n", $t, $y, abs($y - ($t**2 + 4)**2 / 16)
+    if $t == $t.Int;
+}
-for @t Z @y -> $t, $y {
+</lang>
-    printf "y(%2d) = %12f ± %e\n", $t, $y, abs( $y - ($t**2 + 4)**2 / 16)
-    if $t == $t.floor;
-}</lang>
 {{out}}
 <pre>y( 0) =     1.000000 ± 0.000000e+00