X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;ds=sidebyside;f=matita%2Fmatita%2Flib%2Fbasics%2Ftypes.ma;h=b7a022ad201056d7d5d1842ea9b3def64d0d862b;hb=734814ac0ecee6e2e6db6637bbd6acb88b505585;hp=46cc5dd4be8c0c1a1d25374fa7c2fcdc972d2369;hpb=910b8e95135bfabb852c2e6d918ff50bdcb98d0a;p=helm.git

diff --git a/matita/matita/lib/basics/types.ma b/matita/matita/lib/basics/types.ma
index 46cc5dd4b..b7a022ad2 100644
--- a/matita/matita/lib/basics/types.ma
+++ b/matita/matita/lib/basics/types.ma
@@ -145,10 +145,10 @@ for @{ match $t return λx.x = $t → ? with [ mk_Prod ${fresh xy} ${ident z} 
        match ${fresh xy} return λx. ? = $t → ? with [ mk_Prod ${ident x} ${ident y} ⇒
         λ${ident E}.$s ] ] (refl ? $t) }.
 
-notation < "hvbox('let' \nbsp hvbox(〈ident x,ident y,ident z〉 \nbsp'as'\nbsp ident E\nbsp ≝ break t \nbsp 'in' \nbsp) break s)"
+notation < "hvbox('let' \nbsp hvbox(〈ident x,ident y,ident z〉 \nbsp 'as' \nbsp ident E\nbsp ≝ break t \nbsp 'in' \nbsp) break s)"
  with precedence 10
-for @{ match $t return λ${ident x}.$eq $T $x $t → $U with [ mk_Prod (${fresh xy}:$V) (${ident z}:$Z) ⇒
-       match ${fresh xy} return λ${ident y}. $eq $R $r $t → ? with [ mk_Prod (${ident x}:$L) (${ident y}:$I) ⇒
+for @{ match $t return λ${ident k}:$X.$eq $T $k $t → $U with [ mk_Prod (${ident xy}:$V) (${ident z}:$Z) ⇒
+       match $xy return λ${ident a}. $eq $R $r $t → ? with [ mk_Prod (${ident x}:$L) (${ident y}:$I) ⇒
         λ${ident E}:$J.$s ] ] ($refl $A $t) }.
 
 notation > "hvbox('let' 〈ident w,ident x,ident y,ident z〉 ≝ t 'in' s)"
@@ -214,3 +214,10 @@ lemma pair_destruct_2:
  ∀A,B.∀a:A.∀b:B.∀c. 〈a,b〉 = c → b = \snd c.
  #A #B #a #b *; /2/
 qed.
+
+lemma coerc_pair_sigma:
+ ∀A,B,P. ∀p:A × B. P (\snd p) → A × (Σx:B.P x).
+#A #B #P * #a #b #p % [@a | /2/]
+qed.
+coercion coerc_pair_sigma:∀A,B,P. ∀p:A × B. P (\snd p) → A × (Σx:B.P x)
+≝ coerc_pair_sigma on p: (? × ?) to (? × (Sig ??)).