Version: 5.1
6 Dictionaries
| (require unstable/dict) |
This library is unstable;
compatibility will not be maintained.
See Unstable for more information.
This module provides tools for manipulating dictionary values.
6.1 Dictionary Constructors
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| mutable? : boolean? = weak? | |||||||||||||||||||||
| weak? : boolean? = #f | |||||||||||||||||||||
| compare : (or/c 'eq 'eqv 'equal) = equal |
Constructs an empty hash table based on the behavior specified by
mutable?, weak?, and compare.
Examples: |
| > (empty-dict) |
'#hash() |
| > (empty-dict #:mutable? #t) |
'#hash() |
| > (empty-dict #:weak? #t) |
'#hash() |
| > (empty-dict #:compare 'eqv) |
'#hasheqv() |
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| d : dict? | ||||||||||||||||||||||||||||
| mutable? : boolean? = weak? | ||||||||||||||||||||||||||||
| weak? : boolean? = #f | ||||||||||||||||||||||||||||
| compare : (or/c 'eq 'eqv 'equal) = equal |
Converts a given dictionary d to a hash table based on the behavior
specified by mutable?, weak?, and compare.
Examples: |
| > (make-dict '([1 . one] [2 . two])) |
'#hash((1 . one) (2 . two)) |
| > (make-dict '([1 . one] [2 . two]) #:mutable? #t) |
'#hash((1 . one) (2 . two)) |
| > (make-dict '([1 . one] [2 . two]) #:weak? #t) |
'#hash((1 . one) (2 . two)) |
| > (make-dict '([1 . one] [2 . two]) #:compare 'eqv) |
'#hasheqv((1 . one) (2 . two)) |
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| equiv? : (-> any/c any/c any/c) | |||||||||||||||||||||||||||||||||||
| hash-primary : (-> any/c exact-integer?) = (lambda (x) 0) | |||||||||||||||||||||||||||||||||||
| hash-secondary : (-> any/c exact-integer?) = (lambda (x) 0) | |||||||||||||||||||||||||||||||||||
| mutable? : boolean? = weak? | |||||||||||||||||||||||||||||||||||
| weak? : boolean? = #f |
Constructs a dictionary based on custom comparison and optional hash functions.
Given no hash functions, the dictionary defaults to a degenerate hash function
and is thus essentially equivalent to a list-based dictionary.
Examples: | ||
| ||
| > (dict-set! table 1 'one) | ||
| > (dict-set! table 2 'two) | ||
| ||
'((2 . two) (1 . one)) |
6.2 Dictionary Lookup
| (dict-ref/check d k) → any/c |
| d : dict? |
| k : (lambda (k) (dict-has-key? d k)) |
Looks up key k in dictionary d. Raises a contract error if
d has no entry for k. Equivalent to (dict-ref d k),
except for the specific exception value raised.
Example: |
| > (dict-ref/check '([1 . one] [2 . two] [3 . three]) 2) |
'two |
| (dict-ref/identity d k) → any/c |
| d : dict? |
| k : any/c |
Looks up key k in dictionary d. Returns k if
d has no entry for k. Equivalent to
(dict-ref d k (lambda () k)).
Examples: |
| > (dict-ref/identity '([1 . one] [2 . two] [3 . three]) 2) |
'two |
| > (dict-ref/identity '([1 . one] [2 . two] [3 . three]) 4) |
4 |
| (dict-ref/default d k v) → any/c |
| d : dict? |
| k : any/c |
| v : any/c |
Looks up key k in dictionary d. Returns v if
d has no entry for k. Equivalent to
(dict-ref d k (lambda () v)).
Examples: |
| > (dict-ref/default '([1 . one] [2 . two] [3 . three]) 2 'other) |
'two |
| > (dict-ref/default '([1 . one] [2 . two] [3 . three]) 4 'other) |
'other |
Looks up key k in dictionary d. Returns the result of
applying f (in tail position) if d has no entry for
k. Equivalent to (dict-ref d k f).
Examples: |
| > (dict-ref/failure '([1 . one] [2 . two] [3 . three]) 2 gensym) |
'two |
| > (dict-ref/failure '([1 . one] [2 . two] [3 . three]) 4 gensym) |
'g3495 |
6.3 Dictionary Accessors
| (dict-empty? d) → boolean? |
| d : dict? |
Reports whether d is empty (has no keys).
Examples: |
| > (dict-empty? '()) |
#t |
| > (dict-empty? '([1 . one] [2 . two])) |
#f |
6.4 Dictionary Combinations
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| → (and/c dict? dict-can-functional-set?) | ||||||||||||||||
| d0 : (and/c dict? dict-can-functional-set?) | ||||||||||||||||
| d : dict? | ||||||||||||||||
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|
Computes the union of d0 with each dictionary d by functional
update, adding each element of each d to d0 in turn. For each
key k and value v, if a mapping from k to some value
v0 already exists, it is replaced with a mapping from k to
(combine/key k v0 v).
Examples: | |||
| > (dict-union '([1 . one]) '([2 . two]) '([3 . three])) | |||
'((1 . one) (2 . two) (3 . three)) | |||
| |||
'((1 one uno ein une) (2 two dos zwei deux)) |
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| d0 : (and/c dict? dict-mutable?) | ||||||||||||||||||||||||||||
| d : dict? | ||||||||||||||||||||||||||||
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|
Computes the union of d0 with each dictionary d by mutable
update, adding each element of each d to d0 in turn. For each
key k and value v, if a mapping from k to some value
v0 already exists, it is replaced with a mapping from k to
(combine/key k v0 v).
Examples: | |||
| |||
| > d | |||
'#hash() | |||
| > (dict-union! d '([1 one uno] [2 two dos])) | |||
| > d | |||
'#hash((1 . (one uno)) (2 . (two dos))) | |||
| |||
| > d | |||
'#hash((1 . (one uno ein une)) (2 . (two dos zwei deux))) |
6.5 Dictionary Structure Properties
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| unwrap : (-> (and/c dict? pred) dict?) | ||||||||||||||||||||||||||||||||||||||||||
| wrap : (-> dict? (and/c dict? pred)) = (lambda (x) x) | ||||||||||||||||||||||||||||||||||||||||||
| pred : (-> any/c boolean?) = (lambda (x) #t) | ||||||||||||||||||||||||||||||||||||||||||
| mutable? : boolean? = weak? | ||||||||||||||||||||||||||||||||||||||||||
| mutable? : boolean? = #f | ||||||||||||||||||||||||||||||||||||||||||
| functional? : boolean? = #t |
Produces a value appropriate for prop:dict for a derived dictionary
type recognized by pred. Dictionaries constructed from this property
will extract a nested dictionary using unwrap and will produce a
wrapped dictionary during functional update using wrap.
Examples: | ||||||||
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| > (dict? (make-table '([1 . one] [2 . two]))) | ||||||||
#t | ||||||||
| > (dict-ref (make-table '([1 . one] [2 . two])) 1) | ||||||||
'one | ||||||||
| > (dict-set (make-table '([1 . one] [2 . two])) 3 'three) | ||||||||
(table '((1 . one) (2 . two) (3 . three))) |
6.6 Contracted Dictionaries
This library re-provides dict/c from unstable/contract.