What is a Purely Functional Language? (1998)
| Venue: | Journal of Functional Programming |
| Citations: | 14 - 5 self |
BibTeX
@ARTICLE{Sabry98whatis,
author = {Amr Sabry},
title = {What is a Purely Functional Language?},
journal = {Journal of Functional Programming},
year = {1998},
volume = {8},
pages = {1--22}
}
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Abstract
Functional programming languages are informally classified into pure and impure languages. The precise meaning of this distinction has been a matter of controversy. We therefore investigate a formal definition of purity. We begin by showing that some proposed definitions that rely on confluence, soundness of the beta axiom, preservation of pure observational equivalences, and independence of the order of evaluation, do not withstand close scrutiny. We propose instead a definition based on parameter-passing independence. Intuitively, the definition implies that functions are pure mappings from arguments to results; the operational decision of how to pass the arguments is irrelevant. In the context of Haskell, our definition is consistent with the fact that the traditional call-by-name denotational semantics coincides with the traditional call-by-need implementation. Furthermore, our definition is compatible with the stream-based, continuationbased, and monad-based integration of computa...
Keyphrases
functional language monad-based integration impure language beta axiom pure observational equivalence operational decision formal definition pure mapping traditional call-by-name denotational semantics coincides precise meaning parameter-passing independence traditional call-by-need implementation functional programming language
