Evaluation algorithm changed to inverted interleaved depth first search

1 files changed, 17 insertions, 11 deletions

diff --git a/test/fivesix.adb b/test/fivesix.adb
index 9620c60..781b7c3 100644
--- a/test/fivesix.adb
+++ b/test/fivesix.adb
@@ -24,7 +24,6 @@ procedure FiveSix is
     use InPrin;
 
 
-    --  It is possible to create a recursion using functions like this...
     function Fives
            (This : in Goal)
         return Goal
@@ -36,9 +35,19 @@ procedure FiveSix is
         return Disjunct (One, Two);
     end Fives;
 
+    function Sixes
+           (This : in Goal)
+        return Goal
+    is
+        One, Two : Goal := This;
+    begin
+        One.Unify (One.Fresh, 6);
+        Two.Conjunct (Sixes'Access);
+        return Disjunct (One, Two);
+    end Sixes;
+
 
-    Sixes : Goal := Empty_Goal;
-    Result : Goal;
+    Relation : constant Goal := Disjunct (Fives (Empty_Goal), Sixes (Empty_Goal));
 
 begin
 
@@ -47,14 +56,11 @@ begin
 
     TIO.New_Line;
 
-    --  ...but it is a lot simpler and easier to create recursions this way instead.
-    Sixes.Unify (Sixes.Fresh, 6);
-    Sixes.Recurse;
-
-    Result := Disjunct (Fives (Empty_Goal), Sixes);
-
-    --  Note how the States from Fives keep creating new Variables instead of looping.
-    TIO.Put_Line (Image (Result.Run (5)));
+    --  Note how the States keep using new Variables instead of just reusing the same one.
+    --  This is an unavoidable side effect of setting up Variable Terms to be manually
+    --  created from a Goal by the programmer, instead of being supplied as needed in the
+    --  process of evaluation.
+    TIO.Put_Line (Image (Relation.Run (5)));
 
 end FiveSix;