# Terms

(Difference between revisions)

##  An overview of Haskell related terms

 Abstract algebra Abstract algebra is the subject area of mathematics that studies algebraic structures, such as groups, rings, fields, modules, vector spaces, and algebras. Adjoint functors See the Wikipedia article Anamorphism An unfold Bijection In mathematics, a bijection is a function that is both one-to-one (injective) and onto (surjective). Bottom Undefined value Catamorphism Fold; any for-each loop can be represented as a catamorphism Category theory Category theory is an area of study in mathematics that examines in an abstract way the properties of particular mathematical concepts, by formalising them as collections of objects and arrows (also called morphisms, although this term also has a specific, non category-theoretical sense), where these collections satisfy certain basic conditions. Finally tagless ??? Forgetful functor Given some object with structure as input, some or all of the object's structure or properties is 'forgotten' in the output Functional reference A reference into a data structure. See Overloading functional references Homomorphism In abstract algebra, a homomorphism is a structure-preserving map between two algebraic structures (such as groups, rings, or vector spaces). Hylomorphism Combination of fold and unfold; every for-loop (without early exits) can be represented as a hylomorphism Isomorphism In abstract algebra, an isomorphism is a bijective map f such that both f and its inverse f−1 are homomorphisms Left adjoint See the Wikipedia article on adjoint functors Oleg rating A measure of ability to do type system trickery, named after Oleg Kiselyov :) Partial application Partial application in Haskell involves passing less than the full number of arguments to a function that takes multiple arguments. Right adjoint See the Wikipedia article on adjoint functors Tail recursion A recursive function is tail recursive if the final result of the recursive call is the final result of the function itself. Tying the knot Building a cyclic data structure Unboxed tuple Unboxed tuples are used for functions that need to return multiple values, but they avoid the heap allocation normally associated with using fully-fledged tuples. Unlifted types Types that do not have bottom as an inhabitant Unpointed types Types that do not have bottom as an inhabitant