lenses

Documentation

A Racket package for creating and composing pure functional lenses. A lens is a function that examines a small subpiece of some larger structure. When given a value of that larger structure, the lens returns two values: a view value, which is the subpiece, and a context function, which accepts a new view value and returns a new structure with the old view replaced by the new view. Think of them as composable, pure functional getters and setters. Examples can be found in the documentation.