diff options
Diffstat (limited to 'src/kompsos.adb')
| -rw-r--r-- | src/kompsos.adb | 75 |
1 files changed, 46 insertions, 29 deletions
diff --git a/src/kompsos.adb b/src/kompsos.adb index d018c27..3981005 100644 --- a/src/kompsos.adb +++ b/src/kompsos.adb @@ -235,7 +235,10 @@ package body Kompsos is Item : in Term'Class) return Term'Class is begin - if This.Subst.Contains (Item.Actual.Refer.Ident) then + if Item.Actual /= null and then + Item.Actual.Kind = Var_Term and then + This.Subst.Contains (Item.Actual.Refer.Ident) + then return Walk (This, This.Subst.Constant_Reference (Item.Actual.Refer.Ident)); else return Item; @@ -268,24 +271,48 @@ package body Kompsos is end if; end if; - -- Check for null Terms + -- Check for equal null Terms if Real_Left.Actual = null and Real_Right.Actual = null then Extended := Potential; return True; end if; - if Real_Left.Actual = null or Real_Right.Actual = null then - return False; - end if; -- Unify equal Variable Terms - if Real_Left.Actual.Kind = Var_Term and then - Real_Right.Actual.Kind = Var_Term and then + if Real_Left.Actual /= null and then Real_Left.Actual.Kind = Var_Term and then + Real_Right.Actual /= null and then Real_Right.Actual.Kind = Var_Term and then Real_Left = Real_Right then Extended := Potential; return True; end if; + -- Unify Variable and other Terms by introducing a new substitution + if Real_Left.Actual /= null and then Real_Left.Actual.Kind = Var_Term then + if Real_Right.Actual /= null and then Real_Right.Actual.Kind = Pair_Term and then + not Fully_Contains (Potential, Real_Right) + then + return False; + end if; + Extended := Potential; + Extended.Subst.Insert (Real_Left.Actual.Refer.Ident, Term (Real_Right)); + return True; + end if; + if Real_Right.Actual /= null and then Real_Right.Actual.Kind = Var_Term then + if Real_Left.Actual /= null and then Real_Left.Actual.Kind = Pair_Term and then + not Fully_Contains (Potential, Real_Left) + then + return False; + end if; + Extended := Potential; + Extended.Subst.Insert (Real_Right.Actual.Refer.Ident, Term (Real_Left)); + return True; + end if; + + -- Don't want any null terms beyond here + if Real_Left.Actual = null or Real_Right.Actual = null then + return False; + end if; + -- Unify equal Atom Terms if Real_Left.Actual.Kind = Atom_Term and then Real_Right.Actual.Kind = Atom_Term and then @@ -311,28 +338,6 @@ package body Kompsos is end; end if; - -- Unify Variable and other Terms by introducing a new substitution - if Real_Left.Actual.Kind = Var_Term then - if Real_Right.Actual.Kind = Pair_Term and then - not Fully_Contains (Potential, Real_Right) - then - return False; - end if; - Extended := Potential; - Extended.Subst.Insert (Real_Left.Actual.Refer.Ident, Term (Real_Right)); - return True; - end if; - if Real_Right.Actual.Kind = Var_Term then - if Real_Left.Actual.Kind = Pair_Term and then - not Fully_Contains (Potential, Real_Left) - then - return False; - end if; - Extended := Potential; - Extended.Subst.Insert (Real_Right.Actual.Refer.Ident, Term (Real_Left)); - return True; - end if; - -- Not sure how things get here, but if all else fails return False; end Do_Unify; @@ -491,6 +496,18 @@ package body Kompsos is -- Public API Operations -- ----------------------------- + -- Query -- + + function Failed + (This : in out World) + return Boolean is + begin + return not This.Has_State (1); + end Failed; + + + + -- Fresh -- function Fresh |