Hope (programming language): Difference between revisions

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{{Infobox programming language

'''Hope''' is a small [[functional programming language]] developed in the 1970s at the [[University of Edinburgh]].<ref name="BMS">[[Rod Burstall|Burstall R.M]], MacQueen D.B, Sannella D.T. (1980) ''Hope: An Experimental Applicative Language''. Conference Record of the 1980 LISP Conference, Stanford University, pp. 136-143.</ref><ref>

| name = Hope

{{cite book

| logo = <!-- Filename -->

| title = Functional Programming with Hope

| logo caption =

| series = Ellis Horwood Series in Computers and Their Applications

| screenshot = <!-- Filename -->

| last = Bailey

| screenshot caption =

| first = Roger

| sampleCode =

| publisher = Ellis Horwood Ltd

| paradigm = [[Functional programming|functional]]

| date = 1 April 1990

| issuefamily = 8

}}</ref>

| designers = [[Rod Burstall]]<br>D. B. MacQueen<br>[[Don Sannella]]

It predates [[Miranda programming language|Miranda]] and [[Haskell (programming language)|Haskell]] and is contemporaneous with [[ML (programming language)|ML]], also developed at the University. Hope was derived from [[NPL (programming language)|NPL]],<ref name="design"/> a simple functional language developed by [[Rod Burstall]] and John Darlington in their work on program transformation.<ref>R.M. Burstall and J. Darlington. A transformation system for developing recursive programs. Journal of the Association for Computing Machinery, 24(1):44–67 (1977)</ref> NPL and Hope are notable for being the first languages with call-by-pattern evaluation and [[algebraic data types]].<ref>{{Cite book|last=Hudak|first=Paul|last2=Hughes|first2=John|last3=Peyton Jones|first3=Simon|last4=Wadler|first4=Philip|date=2007-06-09|title=A history of Haskell: being lazy with class|publisher=ACM|pages=12–1|doi=10.1145/1238844.1238856|isbn=9781595937667}}</ref>

| developer =[[University of Edinburgh]]

| released = {{Start date and age|1980}}

| latest release version =

| latest release date = <!-- {{Start date and age|199y|mm|dd|df=yes}} -->

| typing =

| memory management =

| scope =

| programming language =

| discontinued = Yes

| platform =

| operating system =

| license =

| file ext =

| file format = <!-- or: | file formats = -->

| website = <!-- {{URL|www.example.com}} -->

| implementations =

| dialects = Hope+

| influenced by = [[NPL (programming language)|NPL]]

| influenced =

}}

'''Hope''' is a small[[programming language]] based on [[functional programming language]] developed in the 1970s at the [[University of Edinburgh]].<ref name="BMS">[[Rod{{cite book Burstall|last1=Burstall |first1=R. M]],. |author1-link=Rod Burstall |last2=MacQueen |first2=D. B,. |last3=Sannella |first3=D. T. (|date=1980) ''|chapter=Hope: An Experimental Applicative Language'' |title=Proc. Conference Record of the 1980 LISP Conference|place=Stanford University, Stanford, UniversityCalifornia, pp.United 136-143States |page=136–143 |url=https://homepages.inf.ed.ac.uk/dts/pub/hope.pdf}}</ref><ref>

Hope was named for [[Sir Thomas Hope, 8th Baronet|Sir Thomas Hope]] (c. 1681–1771), a Scottish agricultural reformer, after whom ''Hope Park Square'' in Edinburgh, the ___location of the Department of Artificial Intelligence at the time of the development of Hope, was also named.

{{cite book |last1=Bailey |first1=Roger |date=1 April 1990 |title=Functional Programming with Hope |series=Ellis Horwood Series in Computers and Their Applications |publisher=Ellis Horwood Ltd}}</ref>

It predates [[Miranda (programming language)|Miranda]] and [[Haskell (programming language)|Haskell]] and is contemporaneous with [[ML (programming language)|ML]], also developed at the University. Hope was derived from [[NPL (programming language)|NPL]],<ref name="design"/> a simple functional language developed by [[Rod Burstall]] and [[John Darlington]] in their work on program transformation.<ref>{{cite journal |last1=Burstall |first1=R. M. |author1-link=Rod Burstall and|last2=Darlington |first2=J. |author2-link=John Darlington. |date=1977 |title=A transformation system for developing recursive programs. |journal=Journal of the Association for Computing Machinery, |volume=24( |issue=1):44–67 (1977)|pages=44–67}}</ref> NPL and Hope are notable for being the first languages with call-by-pattern evaluation and [[algebraic data typestype]]s.<ref>{{Cite book |lastlast1=Hudak |firstfirst1=Paul |author1-link=Paul Hudak |last2=Hughes |first2=John |author2-link=John Hughes (computer scientist) |last3=Peyton Jones |first3=Simon |author3-link=Simon Peyton Jones |last4=Wadler |first4=Philip |author4-link=Philip Wadler |date=2007-06-09 |title=A history of Haskell: being lazy with class |publisher=ACM |pages=12–1 |doi=10.1145/1238844.1238856 |isbn=9781595937667 |s2cid=52847907}}</ref>

Hope was named for [[Sir Thomas Hope, 8th Baronet|Sir Thomas Hope]] (c. 1681–1771), a Scottish agricultural[[agriculture]] reformer, after whom ''Hope Park Square'' in [[Edinburgh]], the ___location of the Department[[artificial of Artificialintelligence]] Intelligencedepartment at the time of the development of Hope, was also named.

The first implementation of Hope used [[strict evaluation]], but there have since been [[lazy evaluation]] versions and strict versions with lazy constructors. A successor language Hope+, developed jointly between [[Imperial College]] and [[International Computers Limited]], added annotations to dictate either strict or lazy evaluation.<ref name=annotations>{{cite book |last1=Kewley |first1=John |last2=Glynn |first2=Kevin |date=1989 |chapter=Evaluation Annotations for Hope+ |editor1-last=Davis |editor1-first=Kei |editor2-last=Hughes |editor2-first=R. J. M. |title=Functional Programming: Proceedings of the 1989 Glasgow Workshop, Workshops in Computing |pages=329–337 |place=London, United Kingdom |publication-date=1990 |publisher=[[Springer-Verlag]]}}</ref>

==Language details==

A [[factorial]] program in Hope is:

dec fact : num -> num;

--- fact 0 <= 1;

--- fact n <= n*fact(n-1);

Changing the order of the clauses does not change the meaning of the program, because Hope's pattern matching always favors more specific patterns over less specific ones. Explicit type[[Declaration (computer programming)|declarations]] of [[data type]]s in Hope are required; there is no option[[type to use a type-inference]] algorithm in Hope.

<source lang="haskell">

dec fact : num -> num;

--- fact 0 <= 1;

--- fact n <= n*fact(n-1);

</source>

Changing the order of the clauses does not change the meaning of the program, because Hope's pattern matching always favors more specific patterns over less specific ones. Explicit type declarations in Hope are required; there is no option to use a type-inference algorithm in Hope.

Hope provides two built-in [[data structuresstructure]]s: tuples[[tuple]]s and [[List (abstract data type)|lists]].<ref name=byte/>

==Implementations==

TheRoger firstBailey's implementationHope oftutorial Hopein wasthe August 1985 issue of ''[[strictByte evaluation(magazine)|strictByte]],'' butreferences since that one there have beenan [[lazyInterpreter evaluation(computing)|lazyinterpreter]] versionsfor and[[IBM strictPC versionsDOS]] with2.0.<ref lazyname=byte/> constructors.[[BT Group|British Telecom]] embarked on a project with [[Imperial College London|Imperial College]] to implement a strict version of Hope. The first release was coded by Thanos Vassilakis in 1986. Further releases were coded by Mark Tasng of British Telecom.

Roger Bailey's Hope tutorial in the August 1985 issue of ''[[Byte (magazine)|BYTE]]'' references an interpreter for [[IBM PC DOS]] 2.0.<ref name=byte/>

==References==

{{Reflist|refs=

<ref name="design">{{cite conference |last1=Burstall |first1=R. M. |author1-link=Rod Burstall. |date=1977 |title=Design considerations for a functional programming language. Invited(invited paper,) Proc.|conference=Proceedings Infotech State of the Art Conf.Conference “The"The Software Revolution”,Revolution" |place=Copenhagen, |pages=45–57 (1977)}}</ref>

<ref name=byte>{{cite magazine |last1=Bailey |first1=Roger |date=August 1985 |url=https://archive.org/stream/BYTE_Vol_10-08_1985-08_The_Amiga#page/n241/mode/2up |title=A Hope Tutorial |magazine=[[Byte (magazine)|Byte]] |volume=10 |issue=8 |page=235–258 |access-date=13 January 2025}}</ref>

<ref name=byte>

{{cite magazine

| title = A Hope Tutorial

| last = Bailey

| first = Roger

| magazine = [[Byte magazine|BYTE]]

| volume = 10

| issue = 8

| date = August 1985

| url = https://archive.org/stream/BYTE_Vol_10-08_1985-08_The_Amiga#page/n241/mode/2up

| accessdate = 1 April 2015

}}</ref>

}}

==External links==

*[https://web.archive.org/web/20130801064002/http://www.hopemachine.co.uk/ Hope Interpreter for Windows]

*[http://cgibin.erols.com/ziring/cgi-bin/cep/cep.pl?_key=Hope Entry in the online Dictionary of Programming Languages]

{{Authority control}}

{{DEFAULTSORT:Hope (Programming Language)}}

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