LISP and Symbolic Computation, 5(4)343-375
First-Class Extents
Shinn-Der Lee, Computer Science Department, Indiana University, Bloomington, IN 47405, USA
Daniel P. Friedman, Computer Science Department, Indiana University, Bloomington, IN 47405, USA
Abstract: Abstract Adding environments as first-class entities
to a language can greatly enhance its expressiveness. But first-class
environments rely on identifiers, the syntax of variables, and thus do
not mesh well with lexically-scoped languages. We present first-class
extents as an alternative. First-class extents are founded upon
lexical variables with dynamic extent. They are defined directly on
the variables themselves rather than on their syntax. They therefore
do not cause variable name capturing problems that plague first-class
environments. Moreover, distinguishing variables from locations allows
first-class extents to be orthogonal to imperative and control
features.
Keywords: identifier, variable, location, scope, extent, state
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