Functions for Manipulating these Objects

Consider a typical ``stack'' of control frames.

Suppose the model required that we express the idea of ``the most recent frame whose return program counter points into MAIN.''

The natural expression of this notion involves

function application -- ``fetch the return-pc of this frame''

case analysis -- ``if the pc is MAIN, then ...''

iteration or recursion -- ``pop this frame off and repeat.''

The designers of ACL2 have taken the position that a programming language is the natural language in which to define such notions, provided the language has a mathematical foundation so that models can be analyzed and properties derived logically.

Common Lisp is the language supported by ACL2. To be precise, a small applicative subset of Common Lisp is the language supported by ACL2.