This short article presents an algorithm for bracket abstraction [1] which avoids a combinatorial explosion in the size of the resulting expression when applied repeatedly for abstraction in a series of variables. It differs from a previous solution [2] in introducing only a finite number of additional combinators and in not requiring that all the variables to be abstracted be treated together in a single operation.

Abstract It is shown how by using results from combinatory logic an applicative language, such as LISP, can be translated into a form from which all bound variables have been removed. A machine is described which can efficiently execute the resulting code. This implementation is compared with a conventional interpreter and found to have a number of advantages. Of these the most important is that programs which exploit higher order functions to achieve great compactness of expression are executed much more efficiently.