Add fully working but not terribly optimized versions of infix:<gcd> …

…and infix:<lcm>.

lib/Builtins.cs

@@ -960,6 +960,19 @@ public partial class Builtins {
         return Kernel.NewROScalar(n1);
     }
 
+    static readonly Func<Variable,Variable,Variable> gcd_d = gcd;
+    public static Variable gcd(Variable a1, Variable a2) {
+        int r1, r2;
+        P6any o1 = a1.Fetch(), o2 = a2.Fetch();
+        if (!(o1.mo.is_any && o2.mo.is_any))
+            return HandleSpecial2(a1,a2, o1,o2, minus_d);
+        P6any n1 = GetNumber(a1, o1, out r1);
+        P6any n2 = GetNumber(a2, o2, out r2);
+
+        // SHOULD: optimize for the case of two small sized Ints
+        return MakeInt(BigInteger.GreatestCommonDivisor(PromoteToBigInt(r1, n1), PromoteToBigInt(r2, n2)));
+    }
+
     [TrueGlobal] static IForeignInterpreter p5_interpreter;
     public static Variable eval_perl5(Variable v) {
         P6any o1 = v.Fetch();

lib/CORE.setting

@@ -22,6 +22,14 @@ sub infix:</> is Niecza::builtin('divide',2,2) is equiv<*> ($l,$r) { $l / $r }
 sub infix:<%> is Niecza::builtin('mod',2,2) is equiv<*> ($l,$r) { $l % $r }
 sub infix:<**> is Niecza::builtin('pow',2,2)  is Niecza::absprec<w=> is assoc<right> ($l,$r) { $l ** $r }
 
+# sub infix:<gcd>($l,$r) is Niecza::builtin('gcd',2,2) { $l gcd $r }
+sub infix:<gcd>($l,$r)  { Q:CgOp { (gcd {$l.Int} {$r.Int}) } }
+sub infix:<lcm>($l,$r) {
+    my $l-int = $l.Int.abs;
+    my $r-int = $r.Int.abs;
+    $l-int div ($l-int gcd $r-int) * $r-int;
+}
+
 sub next ($x?) { _lexotic(1, $x, ()) }
 sub last ($x?) { _lexotic(2, $x, ()) }
 sub redo ($x?) { _lexotic(3, $x, ()) }