Editing List comprehension (section)

==History==

The existence of related constructs predates the use of the term "List Comprehension". The [[SETL]] programming language (1969) has a set formation construct which is similar to list comprehensions. E.g., this code prints all prime numbers from 2 to {{var|N}}:
 print([n in [2..N] | forall m in {2..n - 1} | n mod m > 0]);
The [[computer algebra system]] [[Axiom (computer algebra system)|AXIOM]] (1973) has a similar construct that processes [[stream (computing)|stream]]s.

The first use of the term "comprehension" for such constructs was in [[Rod Burstall]] and [[John Darlington]]'s description of their functional programming language [[NPL programming language|NPL]] from 1977. In his retrospective "Some History of Functional Programming Languages",<ref>{{cite conference | first = David | last = Turner | url = https://www.cs.kent.ac.uk/people/staff/dat/tfp12/tfp12.pdf | title = Some history of functional programming languages | book-title = International Symposium on Trends in Functional Programming, Springer, Berlin, Heidelberg | pages = 1–20 | year = 2012}}</ref> [[David_Turner_(computer_scientist)|David Turner]] recalls:

{{quote|text=NPL was implemented in POP2 by Burstall and used for Darlington’s work on program transformation (Burstall & Darlington 1977). The language was first order, strongly (but not polymorphically) typed, purely functional, call-by-value. It also had “set expressions” e.g.
:<pre>setofeven (X)  <=  <:x : x in X & even(x):>}}</pre>
}}

In a footnote attached to the term "list comprehension", Turner also notes

{{quote|text=I initially called these ''ZF expressions'', a reference to [[Zermelo–Fraenkel set theory]] — it was [[Philip_Wadler|Phil Wadler]] who coined the better term ''list comprehension''.}}

Burstall and Darlington's work with NPL influenced many functional programming languages during the 1980s, but not all included list comprehensions. An exception was Turner's influential, pure, lazy, functional programming language [[Miranda programming language|Miranda]], released in 1985. The subsequently developed standard pure lazy functional language [[Haskell programming language|Haskell]] includes many of Miranda's features, including list comprehensions.

Comprehensions were proposed as a query notation for databases<ref>[http://portal.acm.org/citation.cfm?coll=GUIDE&dl=GUIDE&id=135271 Comprehensions, a query notation for DBPLs<!-- Bot generated title -->]</ref> and were implemented in the ''[[Heinrich Kleisli|Kleisli]]'' database query language.<ref>[http://portal.acm.org/citation.cfm?id=351241&dl=ACM&coll=portal The functional guts of the Kleisli query system<!-- Bot generated title -->]</ref>