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(* 02110-1301 USA                                                     *)
(********************************************************************** Proof of Huffman algorithm: Huffman.v  The huffman algorithm and its proof of correctness  Definition: huffman Laurent.Thery@inria.fr (2003) **********************************************************************)
Section Huffman.
Variable A : Type.
Variable empty : A.
Variable eqA_dec : forall a b : A, {a = b} + {a <> b}.
Variable m : list A.
Hypothesis frequency_more_than_one : 1 < length (frequency_list eqA_dec m).

(* Specifications: *)
(* The message is not null *)
Theorem not_null_m : m <> nil.
Proof using A eqA_dec frequency_more_than_one m.