X-Git-Url: http://git.megacz.com/?p=coq-hetmet.git;a=blobdiff_plain;f=src%2FNaturalDeduction.v;fp=src%2FNaturalDeduction.v;h=5cf67dba5903c933d5fa388c9fbe3eb9e176527d;hp=cd225da363743886131b8c17b073e651c217e015;hb=fdebbea0c0303b8bba05779f2635c9a0e5c459b7;hpb=5a2f09b19d1cd62dee31e14625e62b32c0a02449

diff --git a/src/NaturalDeduction.v b/src/NaturalDeduction.v
index cd225da..5cf67db 100644
--- a/src/NaturalDeduction.v
+++ b/src/NaturalDeduction.v
@@ -182,6 +182,13 @@ Section Natural_Deduction.
       | T_Branch a b     => nd_prod (nd_id a) (nd_id b)
     end.
 
+  Fixpoint nd_weak' (sl:Tree ??Judgment) : sl /⋯⋯/ [] :=
+    match sl as SL return SL /⋯⋯/ [] with
+      | T_Leaf None      => nd_id0
+      | T_Leaf (Some x)  => nd_weak x
+      | T_Branch a b     => nd_prod (nd_weak' a) (nd_weak' b) ;; nd_cancelr
+    end.
+
   Hint Constructors Structural.
   Lemma nd_id_structural : forall sl, Structural (nd_id sl).
     intros.
@@ -189,6 +196,16 @@ Section Natural_Deduction.
     destruct a; auto.
     Defined.
 
+  Lemma weak'_structural : forall a, Structural (nd_weak' a).
+    intros.
+    induction a.
+    destruct a; auto.
+    simpl.
+    auto.
+    simpl.
+    auto.
+    Qed.
+
   (* An equivalence relation on proofs which is sensitive only to the logical content of the proof -- insensitive to
    * structural variations  *)
   Class ND_Relation :=