Accession Number:

ADA310837

Title:

Controlling Effects.

Descriptive Note:

Doctoral thesis,

Corporate Author:

CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF COMPUTER SCIENCE

Personal Author(s):

Report Date:

1996-05-01

Pagination or Media Count:

145.0

Abstract:

Many computational effects, such as exceptions, state, or nondeterminism, can be conveniently specified in terms of monads. We investigate a technique for uniformly adding arbitrary such effects to ML-like languages, without requiring any structural changes to the programs themselves. Instead, we use monadic reflection, a new language construct for explicitly converting back and forth between representations of effects as behavior and as data. Using monadic reflection to characterize concisely all effects expressible with a given monad, we can give a precise meaning to the notion of simulating one effect by another, more general one. We isolate a simple condition allowing such a simulation, and in particular show that any monadic effect can be simulated by a continuation monad. In other words, under relatively mild assumptions on the base language allowing formation of a suitably large answer type, control becomes a universal effect. Concluding the development, we show that this universal effect can itself be explicitly implemented in terms of only standard first-class continuations callcc and a piece of global state. This means that we can specify an effect such as nondeterminism abstractly, in terms of result lists, then directly obtain from this description a nondeterministic-choice operator performing imperatively-implemented backtracking. We include a full realization of the general construction in Standard ML of New Jersey, and give several programming examples.

Subject Categories:

  • Computer Programming and Software

Distribution Statement:

APPROVED FOR PUBLIC RELEASE