Well-Typed Programs Can’t Be Blamed

  • Philip Wadler
  • Robert Bruce Findler
Conference paper

DOI: 10.1007/978-3-642-00590-9_1

Part of the Lecture Notes in Computer Science book series (LNCS, volume 5502)
Cite this paper as:
Wadler P., Findler R.B. (2009) Well-Typed Programs Can’t Be Blamed. In: Castagna G. (eds) Programming Languages and Systems. ESOP 2009. Lecture Notes in Computer Science, vol 5502. Springer, Berlin, Heidelberg


We introduce the blame calculus, which adds the notion of blame from Findler and Felleisen’s contracts to a system similar to Siek and Taha’s gradual types and Flanagan’s hybrid types. We characterise where positive and negative blame can arise by decomposing the usual notion of subtype into positive and negative subtypes, and show that these recombine to yield naive subtypes. Naive subtypes previously appeared in type systems that are unsound, but we believe this is the first time naive subtypes play a role in establishing type soundness.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • Philip Wadler
    • 1
  • Robert Bruce Findler
    • 2
  1. 1.University of Edinburgh 
  2. 2.University of Chicago 

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