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Summary: Dynamic Typing and Subtype Inference
Alexander Aiken Manuel F¨ahndrich
Computer Science Division
University of California, Berkeley
Berkeley, CA 947201776
faiken,manuelg@cs.berkeley.edu
Abstract
Dynamic typing is a program analysis targeted at removing
runtime tagging and untagging operations in dynamically
typed languages. This paper shows that dynamic typing
at least as powerful as Henglein's system [Hen92b] can be
expressed using set constraints.
1 Introduction
This paper presents a study of Henglein's dynamic typing
discipline [Hen92a, Hen92b]. Dynamic typing extends con
ventional static types with a single new type Dynamic. Spe
cial functions called coercions inject values into and project
values from type Dynamic. Currently, the main application
of dynamic typing is the optimization of programs written
in dynamically typed languages (such as Lisp and Scheme)
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