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[helm.git] / helm / software / matita / nlibrary / logic / connectives.ma

diff --git a/helm/software/matita/nlibrary/logic/connectives.ma b/helm/software/matita/nlibrary/logic/connectives.ma
index 02002dc834a31081c97b26c30cbeb5102ae2f7fe..6eb2375dcc895b3b8e4e6068572345382f349e34 100644 (file)
--- a/helm/software/matita/nlibrary/logic/connectives.ma
+++ b/helm/software/matita/nlibrary/logic/connectives.ma
@@ -18,6 +18,9 @@ ninductive True: CProp ≝
   I : True.
 
 ninductive False: CProp ≝.
+(* elimination principle *)
+ndefinition False_rect ≝ λP: False → Type.λp: False.
+ match p in False return λp. P p with [].
 
 ndefinition Not: CProp → CProp ≝
   λA. A → False.
@@ -38,4 +41,4 @@ interpretation "logical or" 'or x y = (Or x y).
 ninductive Ex (A:Type) (P:A → CProp) : CProp ≝
     ex_intro: ∀x:A. P x → Ex A P.
 
-interpretation "exists" 'exists x = (Ex ? x).
\ No newline at end of file
+interpretation "exists" 'exists x = (Ex ? x).