Blame for all

Amal Ahmed*, Robert Findler, Jeremy G. Siek, Philip Wadler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Several programming languages are beginning to integrate static and dynamic typing, including Racket (formerly PLT Scheme), Perl 6, and C# 4.0 and the research languages Sage (Gronski, Knowles, Tomb, Freund, and Flanagan, 2006) and Thorn (Wrigstad, Eugster, Field, Nystrom, and Vitek, 2009). However, an important open question remains, which is how to add parametric polymorphism to languages that combine static and dynamic typing. We present a system that permits a value of dynamic type to be cast to a polymorphic type and vice versa, with relational parametricity enforced by a kind of dynamic sealing along the lines proposed by Matthews and Ahmed (2008) and Neis, Dreyer, and Rossberg (2009). Our system includes a notion of blame, which allows us to show that when casting between a more-precise type and a less-precise type, any cast failures are due to the less-precisely-typed portion of the program. We also show that a cast from a subtype to its supertype cannot fail.

Original languageEnglish (US)
Pages (from-to)201-214
Number of pages14
JournalACM SIGPLAN Notices
Volume46
Issue number1
DOIs
StatePublished - Jan 1 2011

Keywords

  • Blame tracking
  • Casts
  • Coercions
  • Lambda-calculus

ASJC Scopus subject areas

  • Computer Science(all)

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