alist-lib

SRFI-69-like library for alists

alist-lib

`alist-values`

[procedure] (alist-values alist) → list

Extract the associations from an alist.

alist: The alist from which to extract

(define (alist-values alist) (map cdr alist))

`alist-keys`

[procedure] (alist-keys alist) → list

Extract the keys from an alist.

alist: The alist from which to extract

(define (alist-keys alist) (map car alist))

`alist-map`

[procedure] (alist-map f alist) → list

Map across an alist; f takes two parameters: key and values.

f: The function to apply to each key-value association
alist: The alist to apply to

(define (alist-map f alist)
  (map (match-lambda ((key . values) (f key values))) alist))

`alist-set!`

[syntax] (alist-set! alist key value) → unspecified

Destructively set a key-value association.

alist: The alist in which to set
key: The key to set
value: The value to associate with the key

(define-syntax
  alist-set!
  (lambda (expression rename compare)
    (match expression
           ((_ variable key value)
            (let ((%if (rename 'if))
                  (%null? (rename 'null?))
                  (%set! (rename 'set!))
                  (%list (rename 'list))
                  (%cons (rename 'cons))
                  (%alist-prepend! (rename 'alist-prepend!)))
              `(,%if
                (,%null? ,variable)
                (,%set! ,variable (,%list (,%cons ,key ,value)))
                (,%alist-prepend! ,variable ,key ,value)))))))

[procedure] (alist-update! alist key function) → unspecified
[procedure] (alist-update! alist key function thunk) → unspecified
[procedure] (alist-update! alist key function thunk =) → unspecified

On analogy with hash-table-update!, descructively update an association.

alist: The alist to update
key: The key associated with the update
f: A monadic function taking the preëxisting key
thunk: The thunk to apply if no association exists
=: The equality predicate for keys

(define alist-update!
  (case-lambda
    ((alist key function)
     (alist-update!
       alist
       key
       function
       (lambda () (error "Key not found -- ALIST-UPDATE!" key))))
    ((alist key function thunk) (alist-update! alist key function thunk eqv?))
    ((alist key function thunk =)
     (let ((pair (assoc key alist =)))
       (if pair
         (set-cdr! pair (function (cdr pair)))
         (alist-set! alist key (function (thunk))))))))

`alist-update!/default`

[procedure] (alist-update!/default alist key function default) → unspecified
[procedure] (alist-update!/default alist key function default =) → unspecified

On analogy with hash-table-update!, descructively update an association.

alist: The alist to update
key: The key associated with the update
f: A monadic function taking the preëxisting key
default: The default value if no association exists
=: The equality predicate for keys

(define alist-update!/default
  (case-lambda
    ((alist key function default)
     (alist-update!/default alist key function default eqv?))
    ((alist key function default =)
     (alist-update! alist key function (lambda () default)))))

`alist-ref`

[procedure] (alist-ref alist key) → object
[procedure] (alist-ref alist key thunk) → object
[procedure] (alist-ref alist key thunk =) → object

Return a value associated with its key or apply thunk.

alist: The alist to search in
key: The key whose value to return
thunk: The thunk to apply when association doesn't exist (default is to err)
=: The equality predicate to apply to keys

(define alist-ref
  (case-lambda
    ((alist key)
     (alist-ref
       alist
       key
       (lambda () (error "Key not found -- ALIST-REF" key))))
    ((alist key thunk) (alist-ref alist key thunk eqv?))
    ((alist key thunk =)
     (let ((value (assoc key alist =))) (if value (cdr value) (thunk))))))

`alist-ref/default`

[procedure] (alist-ref/default alist key default) → object
[procedure] (alist-ref/default alist key default =) → object

Return a value associated with its key or default.

alist: The alist to search in
key: The key whose value to return
default: The default to return when association doesn't exist
=: The equality predicate to apply to keys

(define alist-ref/default
  (case-lambda
    ((alist key default) (alist-ref alist key (lambda () default)))
    ((alist key default =) (alist-ref alist key (lambda () default) =))))

`alist-size`

[procedure] (alist-size alist) → integer

Calculate size of alist.

alist: The alist whose size to calculate

(define alist-size length)

`alist-fold`

[procedure] (alist-fold alist f init) → object

Fold an alist; whose f takes key, value, accumulatum.

alist: The alist to fold
f: The function to apply to key, value, accumulatum
init: The seed of the fold

(define (alist-fold alist f init)
  (fold (lambda (association accumulatum)
          (match association ((key . value) (f key value accumulatum))))
        init
        alist))

`alist-set`

[procedure] (alist-set alist key value) → alist

Non-destructively associate a key and value in the alist.

alist: Alist in which to set
key: The key to set
value: The value to associate with key

(define (alist-set alist key value) (alist-cons key value alist))

0.1: Version 0.1
0.1.1: Version 0.1.1
0.1.2: Meta fixes
0.1.3: More meta
0.1.4: Housekeeping
0.2.1: Change to BSD.
0.2.2: Remove debug
0.2.3: Add docs.
0.2.4: Failure condition
0.2.5: With a note about cock-utils
0.2.6: Add test-exit.
0.2.7: alist-set! should work on empty lists.
0.2.8: Remove the dependency on setup-helper-cock.
0.2.9: Remove the dependency on debug.
0.2.10: Use hahn.

Colophon

Documented by hahn.

alist-lib

`alist-values`

`alist-keys`

`alist-map`

`alist-set!`

`alist-update!`

`alist-update!/default`

`alist-ref`

`alist-ref/default`

`alist-size`

`alist-fold`

`alist-set`

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