Data commit

Task/Pi/Raku/pi.raku

@@ -0,0 +1,33 @@
+# based on http://www.mathpropress.com/stan/bibliography/spigot.pdf
+
+sub stream(&next, &safe, &prod, &cons, $z is copy, @x) {
+    gather loop {
+        $z = safe($z, my $y = next($z)) ??
+             prod($z, take $y)          !!
+             cons($z, @x[$++])
+    }
+}
+
+sub extr([$q, $r, $s, $t], $x) {
+    ($q * $x + $r) div ($s * $x + $t)
+}
+
+sub comp([$q,$r,$s,$t], [$u,$v,$w,$x]) {
+    [$q * $u + $r * $w,
+     $q * $v + $r * $x,
+     $s * $u + $t * $w,
+     $s * $v + $t * $x]
+}
+
+my $pi :=
+    stream -> $z { extr($z, 3) },
+           -> $z, $n { $n == extr($z, 4) },
+           -> $z, $n { comp([10, -10*$n, 0, 1], $z) },
+           &comp,
+           <1 0 0 1>,
+           (1..*).map: { [$_, 4 * $_ + 2, 0, 2 * $_ + 1] }
+
+for ^Inf -> $i {
+    print $pi[$i];
+    once print '.'
+}