Data update

Task/Giuga-numbers/Euler/giuga-numbers.euler

@@ -1,35 +0,0 @@
-begin
-   new for; new n; new gCount;
-   for   <- ` formal init; formal test; formal incr; formal body;
-              begin
-                label again;
-                init;
-again:          if test then begin body; incr; goto again end else 0
-              end
-            '
-          ;
-   gCount <- 0;
-   for( ` n <- 2 ', ` gCount < 4 ', ` n <- n + 4 '
-      , ` begin
-             new v; new f; new isGiuga; new fCount;
-             v       <- n % 2;
-             isGiuga <- true;
-             fCount  <- 1;
-             for( ` f <- 3 ', ` f <= v and isGiuga ', ` f <- f + 2 '
-                , ` if v mod f = 0 then begin
-                       fCount  <- fCount + 1;
-                       isGiuga <- [ [ n % f ] - 1 ] mod f = 0;
-                       v <- v % f
-                    end else 0
-                  '
-                );
-             if isGiuga then begin
-                if fCount > 1 then begin
-                   gCount <- gCount + 1;
-                   out n
-                end else 0
-             end else 0
-          end
-        '
-      )
-end $

Task/Giuga-numbers/Lua/giuga-numbers.lua

@@ -0,0 +1,28 @@
+do --[[ find the first 4 Giuga numbers, composites n such that all their
+        distinct prime factors f exactly divide ( n / f ) - 1
+
+        each prime factor must appear only once, e.g.: for 2:
+        [ ( n / 2 ) - 1 ] mod 2 = 0  => n / 2 is odd => n isn't divisible by 4
+        similarly for other primes
+     ]]
+
+    local gCount, n = 0, 2
+    while gCount < 4 do
+        n = n + 4                           -- assume the numbers are all even
+        local fCount, f, isGiuga, v = 1, 1, true, math.floor( n / 2 )
+        while f <= ( v - 2 ) and isGiuga do
+            f = f + 2
+            if v % f == 0 then                          -- have a prime factor
+                fCount  = fCount + 1
+                isGiuga = ( math.floor( n / f ) - 1 ) % f == 0
+                v       = math.floor( v / f )
+            end
+        end
+        if isGiuga then       -- n is still a candidate, check it is not prime
+            if fCount > 1 then
+                gCount = gCount + 1
+                io.write( " ", n )
+            end
+        end
+    end
+end

Task/Giuga-numbers/Sidef/giuga-numbers.sidef

@@ -0,0 +1,3 @@
+4..Inf `by` 2 -> lazy.grep {|n|
+    n.factor.all {|p| p `divides` (n/p - 1) }
+}.first(4).say