Constraint-Based Polymorphism in Cecil:
Towards a Practical and Static Type System
OOPSLA '98, the 13th
ACM Conference on Object-Oriented Programming Systems, Languages and
Applications, October'98
Note. The Conference Proceedings contain, by mistake, a preliminary version of the paper. The actual final version appears in the ACM Digital Library.
Vassily Litvinov
We present a static type system for object-oriented languages which
strives to provide static typechecking without resorting to dynamic
"type casts," restricting what code the programmer can write, or being
too verbose or difficult to use in practice. The type system supports
bounded parametric polymorphism where the bounds on type variables can
be expressed using general recursive subtype or signature constraints,
with F-bounded polymorphism and covariant type parameters being
special cases.
We implemented this type system in the Cecil language and used it to
successfully typecheck a 100,000-line Cecil program, the Vortex
optimizing compiler. Our experience was very good: dynamically-typed
code needed very little rewriting. We also observed several common
programming situations that presented a challenge for our type system.
We discuss these situations and ways to typecheck them statically.
To get the PostScript file, click
here.
To get the PostScript file for an earlier (and more verbose) technical
report (January'98, UW-CSE-98-01-01, with Craig Chambers), click
here.
Cecil/Vortex
Project