Intensional Functions

Functions in functional languages have a single elimination form — application — and cannot be compared, hashed, or subjected to other non-application operations. These operations can be approximated via defunctionalization: functions are replaced with first-order data and calls are replaced with in...

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Bibliographic Details
Published in:Proceedings of ACM on programming languages Vol. 8; no. OOPSLA2; pp. 87 - 112
Main Authors: Palmer, Zachary, Filardo, Nathaniel Wesley, Wu, Ke
Format: Journal Article
Language:English
Published: New York, NY, USA ACM 08.10.2024
Subjects:
Constraints
Control structures
Coroutines
Data types and structures
Functional languages
Procedures, functions and subroutines
Software and its engineering
intensional
closure
continuation
defunctionalization
function
ISSN:2475-1421, 2475-1421
Online Access:Get full text
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Summary:Functions in functional languages have a single elimination form — application — and cannot be compared, hashed, or subjected to other non-application operations. These operations can be approximated via defunctionalization: functions are replaced with first-order data and calls are replaced with invocations of a dispatch function. Operations such as comparison may then be implemented for these first-order data to approximate e.g. deduplication of continuations in algorithms such as unbounded searches. Unfortunately, this encoding is tedious, imposes a maintenance burden, and obfuscates the affected code. We introduce an alternative in intensional functions, a language feature which supports the definition of non-application operations in terms of a function’s definition site and closure-captured values. First-order data operations may be defined on intensional functions without burdensome code transformation. We give an operational semantics and type system and prove their formal properties. We further define intensional monads, whose Kleisli arrows are intensional functions, enabling monadic values to be similarly subjected to additional operations.
ISSN:2475-1421
2475-1421
DOI:10.1145/3689714