2fgxtype

2fgxtype is a formal construct in type theory and computer science used to describe data types parametric in two independent type dimensions. It is a two-parameter type constructor, typically written as 2fgxtype A B, with kind * -> * -> *. In examples, for types A and B, values of 2fgxtype<A,B> pair together an A-portion and a B-portion of data.

Formal properties: It supports bifunctor-like mapping: given functions f:A→A' and g:B→B', there is a map: 2fgxtype f g: 2fgxtype A B → 2fgxtype A' B'. Depending on design, 2fgxtype may be defined as a simple product A×B, or as a richer structure with a relation P(a,b) that constrains valid pairs.

Examples: A simple instantiation is 2fgxtype Int String, consisting of a numeric value and a text label. A more elaborate usage might encode a state that has an input type A and a result type B, where each instance corresponds to a pair (a,b).

Relation to other concepts: It generalizes product types and is related to the notion of a bifunctor in category theory. It also appears in discussions of multi-parameter data models and in some type systems as a shorthand for pairs with extra invariants.

History and usage: The term 2fgxtype is not part of a standard language specification and is mainly encountered in theoretical discussions or niche language designs. See also: product type, bifunctor, dependent pair.