Rank 2 Type Systems and Recursive Definitions
Name
MIT-LCS-TM-531b.pdf
Size
5.19 MB
Format
Unknown
Checksum (MD5)
859a0eaf84b615d8775f7d7c11cf3e1d
Author(s)
Jim, Trevor
Date Issued
November 1995
Series/Report no.
MIT-LCS-TM-531;
Abstract
We demonstrate an equivalence between the rank 2 fragments of the polymorphic lambda calculus (System F) and the intersection type discipline: exactly the same terms are typable in each system. An immediate consequence is that typability in the rank 2 intersection system is DEXPTIME-complete. We introduce a rank 2 system combining intersections and polymorphism and prove that it types exactly the same terms as the other rank 2 systems. The combined system suggests a new rule for typing recursive definitions. The result is a rank 2 type system with decidable type inference that can type some interesting examples of polymorphic recursion. Finally, we discuss some applications of the type system in data representation optimizations such as unboxing and overloading.
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