Escher (programming language)

<h2 id="examples">Examples</h2>
MODULE      Lambda.
CONSTRUCT   Person/0.
FUNCTION    Jane, Mary, John: One -> Person.

FUNCTION    Mother : Person * Person -> Boolean.
Mother(x,y) =>
    x=Jane & y=Mary.

FUNCTION    Wife : Person * Person -> Boolean.
Wife(x,y) =>
    x=John & y=Jane.

FUNCTION    PrimitiveRel : (Person * Person -> Boolean) -> Boolean.
PrimitiveRel(r) =>
    r=Mother \/ r=Wife.

FUNCTION    Rel : (Person * Person -> Boolean) -> Boolean.
Rel(r) =>
    PrimitiveRel(r) \/
    (SOME [r1,r2]
        (r = LAMBDA [u] (SOME [z] (r1(Fst(u),z) & r2(z,Snd(u)))) &
            PrimitiveRel(r1) & PrimitiveRel(r2))).

<ul><li><a href="https://web.archive.org/web/20231008145644/https://www.bristol.ac.uk/engineering/new-structure/?id=1000073">Declarative programming in Escher</a>,[<i>dead link</i>] JW Lloyd, University of Bristol, Bristol, UK, 1995</li>
<li><a href="https://users.cecs.anu.edu.au/~kee/Escher/">An implementation of Escher</a> (Some dead links can be reached from the <a href="https://web.archive.org/web/20211127165402/http://users.cecs.anu.edu.au/~kee/Escher/">archived page</a> (or by substituting the new domain in the link in question).)</li></ul>

Escher (programming language) open-in-new

Escher (programming language)