A lazy evaluator

Abstract

A different way to execute pure LISP programs is presented. It delays the evaluation of parameters and list structures without ever having to perform more evaluation steps than the usual method. Although the central idea can be found in earlier work this paper is of interest since it treats a rather well-known language and works out an algorithm which avoids full substitution. A partial correctness proof using Scott-Strachey semantics is sketched in a later section.