Function that returns equivalent function.

In combinatory logic for computer science, a fixed-point combinator (or fixpoint combinator), is a higher-order function (i.e. a function which takes a function as argument) that returns some fixed point (a value that is mapped to itself) of its argument function, if one exists.

Y Combinator, LLC is an American technology startup accelerator and venture capital firm launched in March 2005 which has been used to launch more than 4,000 companies.

a combinatory logic system and a computational system.

In computer programming, a parser combinator is a higher-order function that accepts several parsers as input and returns a new parser as its output.