--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
+
+set "baseuri" "cic:/matita/LAMBDA-TYPES/Level-1/Preamble".
+
+include "legacy/coq.ma".
+
+(* FG/CSC: These aliases should disappear: we would like to write something
+ * like: "disambiguate in cic:/Coq/*"
+ *)
+alias id "True" = "cic:/Coq/Init/Logic/True.ind#xpointer(1/1)".
+alias id "or" = "cic:/Coq/Init/Logic/or.ind#xpointer(1/1)".
+alias id "nat" = "cic:/Coq/Init/Datatypes/nat.ind#xpointer(1/1)".
+alias id "eq" = "cic:/Coq/Init/Logic/eq.ind#xpointer(1/1)".
+alias id "plus" = "cic:/Coq/Init/Peano/plus.con".
+alias id "le_trans" = "cic:/Coq/Arith/Le/le_trans.con".
+alias id "le_plus_r" = "cic:/Coq/Arith/Plus/le_plus_r.con".
+alias id "le" = "cic:/Coq/Init/Peano/le.ind#xpointer(1/1)".
+alias id "ex" = "cic:/Coq/Init/Logic/ex.ind#xpointer(1/1)".
+alias id "ex2" = "cic:/Coq/Init/Logic/ex2.ind#xpointer(1/1)".
+alias id "true" = "cic:/Coq/Init/Datatypes/bool.ind#xpointer(1/1/1)".
+alias id "false" = "cic:/Coq/Init/Datatypes/bool.ind#xpointer(1/1/2)".
+alias id "bool" = "cic:/Coq/Init/Datatypes/bool.ind#xpointer(1/1)".
+alias id "O" = "cic:/Coq/Init/Datatypes/nat.ind#xpointer(1/1/1)".
+alias id "S" = "cic:/Coq/Init/Datatypes/nat.ind#xpointer(1/1/2)".
+alias id "eq_ind" = "cic:/Coq/Init/Logic/eq_ind.con".
+alias id "or_introl" = "cic:/Coq/Init/Logic/or.ind#xpointer(1/1/1)".
+alias id "or_intror" = "cic:/Coq/Init/Logic/or.ind#xpointer(1/1/2)".
+alias id "False_ind" = "cic:/Coq/Init/Logic/False_ind.con".
+alias id "False" = "cic:/Coq/Init/Logic/False.ind#xpointer(1/1)".
+alias id "I" = "cic:/Coq/Init/Logic/True.ind#xpointer(1/1/1)".
+alias id "minus" = "cic:/Coq/Init/Peano/minus.con".
+
+theorem f_equal: \forall A,B:Type. \forall f:A \to B.
+ \forall x,y:A. x = y \to f x = f y.
+ intros. elim H. reflexivity.
+qed.
+
+theorem sym_eq: \forall A:Type. \forall x,y:A. x = y \to y = x.
+ intros. rewrite > H. reflexivity.
+qed.
+
+theorem sym_not_eq: \forall A:Type. \forall x,y:A. x \neq y \to y \neq x.
+ unfold not. intros. apply H. symmetry. assumption.
+qed.