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revert part of 6c676cf48 because make-custom-hash is actually

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the only way to do certain jobs
This commit is contained in:
Robby Findler 2018-08-23 08:53:35 -05:00
parent 1d3e3d5a08
commit 47ad1552d5
1 changed files with 36 additions and 7 deletions
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43
pkgs/racket-doc/scribblings/reference/dicts.scrbl
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@ -938,7 +938,7 @@ See @racket[define-custom-hash-types] for an example.
(or/c (any/c . -> . exact-integer?)
(any/c (any/c . -> . exact-integer?) . -> . exact-integer?))
(const 1)]
[#:key? key? (any/c . -> . boolean?) (const #true)])
[#:key? key? (any/c . -> . boolean?) (λ (x) #true)])
dict?]
@defproc[(make-weak-custom-hash
[eql?
@ -952,7 +952,7 @@ See @racket[define-custom-hash-types] for an example.
(or/c (any/c . -> . exact-integer?)
(any/c (any/c . -> . exact-integer?) . -> . exact-integer?))
(const 1)]
[#:key? key? (any/c . -> . boolean?) (const #true)])
[#:key? key? (any/c . -> . boolean?) (λ (x) #true)])
dict?]
@defproc[(make-immutable-custom-hash
[eql?
@ -966,15 +966,44 @@ See @racket[define-custom-hash-types] for an example.
(or/c (any/c . -> . exact-integer?)
(any/c (any/c . -> . exact-integer?) . -> . exact-integer?))
(const 1)]
[#:key? key? (any/c . -> . boolean?) (const #true)])
[#:key? key? (any/c . -> . boolean?) (λ (x) #true)])
dict?]
)]{
Constructs an instance of a new dictionary type based on the given comparison
function @racket[eql?], hash functions @racket[hash1] and @racket[hash2], and
key predicate @racket[key?].
Creates an instance of a new dictionary type, implemented
in terms of a hash table where keys are compared with
@racket[eql?], hashed with @racket[hash1] and
@racket[hash2], and where the key predicate is
@racket[key?]. See @racket[gen:equal+hash] for information
on suitable equality and hashing functions.
The @racket[make-custom-hash] and @racket[make-weak-custom-hash]
functions create a mutable dictionary that does not support functional
update, while @racket[make-immutable-custom-hash] creates an immutable
dictionary that supports functional update. The dictionary created by
@racket[make-weak-custom-hash] retains its keys weakly, like the result
of @racket[make-weak-hash].
Dictionaries created by @racket[make-custom-hash] and company are
@racket[equal?] when they have the same mutability and key strength,
the associated procedures are @racket[equal?], and the key--value
mappings are the same when keys and values are compared with
@racket[equal?].
See also @racket[define-custom-hash-types].
@examples[
#:eval dict-eval
(define h (make-custom-hash (lambda (a b)
(string=? (format "~a" a)
(format "~a" b)))
(lambda (a)
(equal-hash-code
(format "~a" a)))))
(dict-set! h 1 'one)
(dict-ref h "1")
]
These procedures are deprecated; use @racket[define-custom-hash-types] instead.
}