Catalan numbers: Difference between revisions

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@@ Line 891: / Line 891: @@
 <lang d>import std.stdio, std.bigint, std.functional;
-BigInt factorial(uint n) {
+BigInt factorial(in uint n) {
-    alias memoize!factorial mfact;
+    alias mfact = memoize!factorial;
-    return n ? mfact(n - 1) * n : BigInt(1);
+    return n ? mfact(n - 1) * n : 1.BigInt;
 }
-auto cats1(uint n) {
+auto cats1(in uint n) {
-    return factorial(2 * n) / (factorial(n + 1) * factorial(n));
+    return factorial(2 * n) / (factorial(n + 1) * n.factorial);
 }
-BigInt cats2(uint n) {
+BigInt cats2(in uint n) {
-    alias memoize!cats2 mcats2;
+    alias mcats2 = memoize!cats2;
-    if (n == 0) return BigInt(1);
+    if (n == 0) return 1.BigInt;
-    auto sum = BigInt(0);
+    BigInt sum = 0;
-    foreach (i; 0 .. n)
+    foreach (immutable i; 0 .. n)
         sum += mcats2(i) * mcats2(n - 1 - i);
     return sum;
 }
-BigInt cats3(uint n) {
+BigInt cats3(in uint n) {
-    alias memoize!cats3 mcats3;
+    alias mcats3 = memoize!cats3;
-    return n ? (4*n - 2) * mcats3(n - 1) / (n + 1) : BigInt(1);
+    return n ? (4*n - 2) * mcats3(n - 1) / (n + 1) : 1.BigInt;
 }
 void main() {
-    foreach (i; 0 .. 15)
+    foreach (immutable i; 0 .. 15)
-        writefln("%2d => %s %s %s", i, cats1(i), cats2(i), cats3(i));
+        writefln("%2d => %s %s %s", i, i.cats1, i.cats2, i.cats3);
 }</lang>
 {{out}}