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Diffstat (limited to 'theories/Logic/ExtensionalFunctionRepresentative.v')
| -rw-r--r-- | theories/Logic/ExtensionalFunctionRepresentative.v | 26 |
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diff --git a/theories/Logic/ExtensionalFunctionRepresentative.v b/theories/Logic/ExtensionalFunctionRepresentative.v new file mode 100644 index 00000000..0aac56bb --- /dev/null +++ b/theories/Logic/ExtensionalFunctionRepresentative.v @@ -0,0 +1,26 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2018 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) + +(** This module states a limited form axiom of functional + extensionality which selects a canonical representative in each + class of extensional functions *) + +(** Its main interest is that it is the needed ingredient to provide + axiom of choice on setoids (a.k.a. axiom of extensional choice) + when combined with classical logic and axiom of (intensonal) + choice *) + +(** It provides extensionality of functions while still supporting (a + priori) an intensional interpretation of equality *) + +Axiom extensional_function_representative : + forall A B, exists repr, forall (f : A -> B), + (forall x, f x = repr f x) /\ + (forall g, (forall x, f x = g x) -> repr f = repr g). |