NPL (programming language): Difference between revisions

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{{for|other programming languages and concepts abbreviated as NPL|NPL (disambiguation)}}

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{{primary sources|date=July 2019}}

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'''NPL''' is a [[Functional programming|functional programming language]] with [[pattern matching]] designed by [[Rod Burstall]] and [[John Darlington]] in 1977. The language allows certain sets and logic constructs to appear on the right -hand side of definitions, e.g.

setofeven(X) <= <:x: x in X & even(x) :>

The NPL interpreter evaluates the list of generators from left to right so conditions can mention any bound variables that occur to their left. These were known as [[set comprehension]]s. NPL eventually evolved into [[Hope programming language|Hope]] but lost set comprehensions, which made a reappearance in the form of [[list comprehension]]s in later functional languages.<ref name="foldoc">{{foldoc|NPL}}</ref>

==References==

{{Reflist}}

* John Darlington (1977). "Program Transformation and Synthesis: Present Capabilities". Research Report No. 77/43, Dept. of Computing and Control, Imperial College of Science and Technology, London.

[[Category:Academic programming languages]]

{{FOLDOC}}

[[Category:Functional languages]]

[[Category:History of computing in the United Kingdom]]

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