This is basically what lambda lifting does. A combinator is a function without any free variables. The transformation ((lambda (x) (F x)) a) ==> ((lambda (

This is basically what lambda lifting does. A combinator is a function without any free variables. The transformation ((lambda (x) (F x)) a) ==> ((lambda (x F) (F x)) a F) ^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^ closure, F is free combinator transforms the applied function into a combinator.