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Fritz Henglein. Dynamic Typing: Syntax and Proof Theory. Science of Computer Progamming (SCP), 22(3):197-230, 1994.


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We present the dynamically typed lambda-calculus, an extension of the statically typed lambda-calculus with a special type Dyn and explicit dynamic type coercions corresponding to run-time type tagging and type check-and-untag operations. Programs in run-time typed languages can be interpreted in the dynamically typed lambda-calculus via a nondeterministic completion process that inserts explicit coercions and type declarations such that a well-typed term results. We characterize when two different completions of the same run-time typed program are coherent with an equational theory that is independent of an underlying I-theory. This theory is refined by orienting some equations to define safety and minimality of completions. Intuitively, a safe completion is one that does not produce an error at run-time which another completion would have avoided, and a minimal completion is a safe completion that executes fewest tagging and check-and-untag operations amongst all safe completions. We show that every untyped lambda-term has a safe completion at any type and that it is unique modulo a suitable congruence relation. Furthermore, we present a rewriting system for generating minimal completions. Assuming strong normalization of this rewriting system we show that every lambda-term has a minimal completion at any type, which is furthermore unique modulo equality in the dynamically typed lambda-calculus


[ Dyntyp ]


Fritz Henglein

BibTex Reference

   Author = {Henglein, Fritz},
   Title = {Dynamic Typing: Syntax and Proof Theory},
   Journal = {Science of Computer Progamming (SCP)},
   Volume = {22},
   Number = {3},
   Pages = {197--230},
   Publisher = {Elsevier North-Holland, Inc},
   Address = {Amsterdam, The Netherlands, The Netherlands},
   Year = {1994}

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