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Extensional Crisis and Proving Identity
[chapter]

2014
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Lecture Notes in Computer Science
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Extensionality axioms are common when reasoning about data collections, such as arrays and functions in program analysis, or sets in mathematics. An extensionality axiom asserts that two collections are equal if they consist of the same elements at the same indices. Using extensionality is often required to show that two collections are equal. A typical example is the set theory theorem (∀x)(∀y)x ∪ y = y ∪ x. Interestingly, while humans have no problem with proving such set identities using

doi:10.1007/978-3-319-11936-6_14
fatcat:fj7nwcr54rhhfjgnbqtypfb3zy