tasks a-s

Task/Permutation-test/Ada/permutation-test-3.ada

@@ -0,0 +1,34 @@
+package body Iterate_Subsets is
+
+   function First return Subset is
+      S: Subset;
+   begin
+      for I in S'Range loop
+         S(I) := I;
+      end loop;
+      return S;
+   end First;
+
+   procedure Next(S: in out Subset) is
+      I: Natural := S'Last;
+   begin
+      if S(I) < Index'Last then
+         S(I) := S(I) + 1;
+      else
+         while S(I-1)+1 = S(I) loop
+            I := I - 1;
+         end loop;
+         S(I-1) := S(I-1) + 1;
+         for J in I .. S'Last loop
+            S(J) := S(J-1) + 1;
+         end loop;
+      end if;
+      return;
+   end Next;
+
+   function Last(S: Subset) return Boolean is
+   begin
+      return S(S'First) = Index'Last-S'Length+1;
+   end Last;
+
+end Iterate_Subsets;