Lambda: The Ultimate Imperative/Abstract
We demonstrate how to model the following common programming constructs in terms of an applicative order language similar to LISP:
- Simple Recursion
- Compound Statements and Expressions
- GO TO and Assignment
- Escape Expressions
- Fluid Variables
- Call by Name, Call by Need, and Call by Reference
The models require only (possibly self-referent) lambda application, conditionals, and (rarely) assignment. No complex data structures such as stacks are used. The models are transparent, involving only local syntactic transformations.
Some of these models, such as those for GO TO and assignment, are already well known, and appear in the work of Landin, Reynolds, and others. The models for escape expressions, fluid variables, and call by need with side effects are new. This paper is partly tutorial in intent, gathering all the models together for purposes of context.
This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract N00014-75-C-0643.