What does hash minus mean?

Question

When to use it and why?

My question comes from the sentence: "hash cons with some classes and compares their instances with referential equality"

Answer 1

Combining all the answers:

ACL2 (A Computational Logic for Applicative Common Lisp) is a software system consisting of a programming language, extensible theory in first-order logic, and verification of a mechanical theorem.

- Wiki ACL2

(/kɒnz/or/kɒns/) Lisp. cons ( ) , . (cons) , conses (cons) . Lisp "to cons x on y" (cons x y). , ( ), ( ), cdr.

- Wiki Cons

, hons - cons, .. ACL2:

( (hons x y) (cons x y))

, , , cdr. -.

- http://www.cs.utexas.edu/~moore/acl2/current/HONS.html

:

hash cons

, hash cons - Lisp , .

Answer 2

Odersky, Spoon and Venners (2007), Scala, Artima Press, p. 243:

hash cons , . , , , . , , , . , (), .

Answer 3

http://en.wikipedia.org/wiki/Hash_cons .

con s , eq () . ( ) , , , .

http://www.cs.utexas.edu/~moore/acl2/current/HONS.html Lisp.