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diff --git a/old-examples/logic/LogicEng.gf b/old-examples/logic/LogicEng.gf
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+--# -path=.:mathematical:present:resource-1.0/api:prelude
+
+concrete LogicEng of Logic = LogicI with
+  (LexTheory = LexTheoryEng), 
+  (Prooftext = ProoftextEng),
+  (Grammar = GrammarEng), 
+  (Symbolic = SymbolicEng), 
+  (Symbol = SymbolEng), 
+  (Combinators = CombinatorsEng), 
+  (Constructors = ConstructorsEng), 
+  ;
+
+{-
+ImplI Abs Abs (\h -> DisjE Abs Abs Abs (DisjIr Abs Abs (Hypoth Abs h)) 
+(\x -> Hypoth Abs x) (\y -> Hypoth Abs y))
+
+assume that we have a contradiction . by the hypothesis we have a contradiction . 
+a fortiori we have a contradiction or we have a contradiction . 
+we have two cases. assume that we have a contradiction . 
+by the hypothesis we have a contradiction . assume that we have a contradiction . 
+by the hypothesis we have a contradiction . therefore we have a contradiction . 
+therefore if we have a contradiction then we have a contradiction .
+-}