Hope is a small
functional programming language developed in the 1970s at the
University of Edinburgh.
[ 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.]
It predates
Miranda and
Haskell and is contemporaneous with
ML, also developed at the University. Hope was derived from
NPL,
a simple functional language developed by
Rod Burstall and
John Darlington
John Darlington is a British academic, researcher and author. He is an Emeritus Professor at Imperial College London. He was Director of the London e-Science Centre and was head of the Functional Programming and Social Computing Sections at Imper ...
in their work on program transformation. NPL and Hope are notable for being the first languages with call-by-pattern evaluation and
algebraic data types.
Hope was named for
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.
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 declarations in Hope are required; there is no option to use a type-inference algorithm in Hope.
Hope provides two built-in data structures: tuples and lists.
[
]
Implementations
The first implementation of Hope was strict
In mathematical writing, the term strict refers to the property of excluding equality and equivalence and often occurs in the context of inequality and monotonic functions. It is often attached to a technical term to indicate that the exclusive ...
, but since that one there have been lazy versions and strict versions with lazy constructors. British Telecom embarked on a project with Imperial College
Imperial College London (legally Imperial College of Science, Technology and Medicine) is a public research university in London, United Kingdom. Its history began with Prince Albert, consort of Queen Victoria, who developed his vision for a cu ...
to implement a strict version. The first release was coded by Thanos Vassilakis in 1986. Further releases were coded by Mark Tasng of British Telecom. A successor language Hope+ (developed jointly between Imperial College
Imperial College London (legally Imperial College of Science, Technology and Medicine) is a public research university in London, United Kingdom. Its history began with Prince Albert, consort of Queen Victoria, who developed his vision for a cu ...
and International Computers Limited
International Computers Limited (ICL) was a British computer hardware, computer software and computer services company that operated from 1968 until 2002. It was formed through a merger of International Computers and Tabulators (ICT), English Ele ...
(ICL) added annotations to dictate either strict or lazy evaluation.[John Kewley and Kevin Glynn. Evaluation Annotations for Hope+. In Kei Davis and R. J. M. Hughes, editors, Functional Programming: Proceedings of the 1989 Glasgow Workshop, Workshops in Computing, pages 329-337, London, UK, 1990. Springer-Verlag.]
Roger Bailey's Hope tutorial in the August 1985 issue of '' BYTE'' references an interpreter for IBM PC DOS 2.0.[
]
References
External links
Hope Interpreter for WindowsEntry for Hope in the online Dictionary of Programming Languages
{{DEFAULTSORT:Hope (Programming Language)
Functional languages
Academic programming languages
History of computing in the United Kingdom
Statically typed programming languages