Dynamic Typing in a Statically Typed Language
ACM Transactions on Programming Languages and Systems, 13 (2):
237--268 (April 1991)Abstract
Statically typed programming languages allow earlier error checking,
better enforcement of disciplined programming styles, and generation
of more efficient object code than languages where all type
consistency checks are performed at run time. However, even in
statically typed languages, there is often the need to deal with data
whose type cannot be determined at compile time. To handle such
situations safely, we propose to add a type Dynamic whose values are
pairs of a value v and a type tag T where v has the type denoted by T.
Instances of Dynamic are built with an explicit tagging construct and
inspected with a type safe typecas construct. This paper explores the
syntax, operational semantics, and denotational semantics of a simple
language including the type Dynamic.
