Title
Preface to the special issue: Isomorphisms of types and invertibility of lambda terms
Abstract
Isomorphisms of types are computational witnesses of logical equivalence with additional properties. The types/formulas A and B are isomorphic if there are functions (in a certain formalism) f : A → B and g : B → A such that g ○ f and f ○ g are equal in a certain sense to the identity on A and B, respectively. Typical such formalisms are extensions of simply typed λ-calculus, with βη-convertibility as equality relation. Another view of a pair of functions f : A → B and g : B → A (besides establishing the logical equivalence of A and B) is that f is invertible with left-inverse g, and it is then natural to relax the above symmetric condition to just g ○ f being equal to the identity on A. In this situation, A is called a retract of B, which is thus a natural generalisation of the notion of an isomorphism, while both these notions are refinements of the concept of logical equivalence in operational terms, that is, in terms of computable functions.
Year
DOI
Venue
2008
10.1017/S0960129508006798
Mathematical Structures in Computer Science
Keywords
Field
DocType
computational logic,lambda calculus and related systems,polymorphism
Discrete mathematics,Logical equivalence,Retract,Generalization,Isomorphism,Formalism (philosophy),Invertible matrix,Rotation formalisms in three dimensions,Computable function,Mathematics
Journal
Volume
Issue
ISSN
18
4
0960-1295
Citations 
PageRank 
References 
0
0.34
0
Authors
2
Name
Order
Citations
PageRank
Ralph Matthes120121.67
Sergei Soloviev210014.57