Hume (programming language): Difference between revisions

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[[File:HumeStatue-Edinburgh2006.jpg|thumb|Hume Statue in Edinburgh]]

'''Hume''' is a functionally based programming language developed at the [[University of St Andrews]] and [[Heriot-Watt University]] in [[Scotland]] since the year 2000. The language name is both an acronym meaning 'Higher-order Unified Meta-Environment' and an honorific to the 18th-century philosopher [[David Hume]]. It targets [[real-time computing]] [[embedded system]]s, aiming to produce a design that is both highly abstract, and yet allows precise extraction of time and space execution costs. This allows guaranteeing the bounded time and space demands of executing programs.

Hume combines [[functional programming]] ideas with ideas from [[finite -state automata]]. Automata are used to structure communicating programs into a series of "boxes", where each box maps [[Input/output|inputs to outputs]] in a [[pure function|purely functional]] way using high-level pattern-matching. It is structured as a series of levels, each of which exposes different machine properties.

== Design model ==

The Hume language design attempts to maintain the essential properties and features required by the embedded systems ___domain (especially for transparent time and space costing) whilst incorporating as high a level of program abstraction as possible. It aims to target applications ranging from simple [[microcontroller]]s to complex real-time systems such as [[smartphone]]s. This ambitious goal requires incorporating both low-level notions such as [[interrupt]] handling, and high-level ones of [[data structure]] abstraction etc. Such systems are programmed in widely differing ways, but the language design should accommodate such varying requirements.

Hume is a three-layer language: an outer (static) declaration/[[metaprogramming]] layer, an intermediate coordination layer describing a static layout of dynamic processes and the associated devices, and an inner layer describing each process as a (dynamic) mapping from patterns to expressions. The inner layer is stateless and purely functional.

Rather than attempting to apply cost modeling and correctness proving technology to an existing language framework either directly or by altering a more general language (as with e.g., [[RTSJ]]), the approach taken by the Hume designers is to design Hume in such a way that formal models and proofs can definitely be constructed. Hume is structured as a series of overlapping language levels, where each level adds expressibility to the expression semantics, but either loses some desirable property or increases the technical difficulty of providing formal correctness/cost models.<ref>{{Cite book |last=Eekelen |first=Marko Van |date=2007 |url=https://books.google.com/books?id=p0yV1sHLubcC |title=Trends in Functional Programming |publisher=Intellect Books |isbn=978-1-84150-176-5 |pages=198 |language=en}}</ref>

== Characteristics ==

The interpreter and compiler versions differ a bit.

* the interpreter (concept prover) admits timeout and custom exceptions.

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== Examples ==

=== Vending machine ===

<syntaxhighlight lang="haskell">

data Coins = Nickel | Dime | Fake;

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* [https://web.archive.org/web/20190403192341/https://www.embounded.org/ EmBounded project], certifies resource-bounded code in Hume

* [https://glew.org/damp2006/Hume-Multicore.pdf Hume and Multicore]

{{Haskell programming}}

[[Category:Haskell programming language family]]