# Computer Laboratory

Technical reports

# Dynamic rebinding for marshalling and update, with destruct-time λ

Gavin Bierman, Michael Hicks, Peter Sewell, Gareth Stoyle, Keith Wansbrough

February 2004, 85 pages

## Abstract

Most programming languages adopt static binding, but for distributed programming an exclusive reliance on static binding is too restrictive: dynamic binding is required in various guises, for example when a marshalled value is received from the network, containing identifiers that must be rebound to local resources. Typically it is provided only by ad-hoc mechanisms that lack clean semantics.

In this paper we adopt a foundational approach, developing core dynamic rebinding mechanisms as extensions to the simply-typed call-by-value λ-calculus. To do so we must first explore refinements of the call-by-value reduction strategy that delay instantiation, to ensure computations make use of the most recent versions of rebound definitions. We introduce redex-time and destruct-time strategies. The latter forms the basis for a λ-marsh calculus that supports dynamic rebinding of marshalled values, while remaining as far as possible statically-typed. We sketch an extension of λ-marsh with concurrency and communication, giving examples showing how wrappers for encapsulating untrusted code can be expressed. Finally, we show that a high-level semantics for dynamic updating can also be based on the destruct-time strategy, defining a λ-update calculus with simple primitives to provide type-safe updating of running code. We thereby establish primitives and a common semantic foundation for a variety of real-world dynamic rebinding requirements.

PDF (0.7 MB)

## BibTeX record

@TechReport{UCAM-CL-TR-568,
author =	 {Bierman, Gavin and Hicks, Michael and Sewell, Peter and
Stoyle, Gareth and Wansbrough, Keith},
title = 	 {{Dynamic rebinding for marshalling and update, with
destruct-time $\lambda$}},
year = 	 2004,
month = 	 feb,
url = 	 {http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-568.pdf},
institution =  {University of Cambridge, Computer Laboratory},
number = 	 {UCAM-CL-TR-568}
}