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Miscellaneous list oriented routines.
- Bugs and Limitations
- Version history
skip+[procedure] (skip+ LIST COUNT) => (list integer)
Returns 2 values, the COUNT pair from LIST, and the remaining count. The remaining count will be non-zero when end-of-list reached.
COUNT is a natural fixnum.
(skip+ '(1 2) 3) ;=> '() 1 (skip+ '(1 2 3) 3) ;=> '() 0 (skip+ '(1 2 3 4) 3) ;=> '(4) 0
split-at+[procedure] (split-at+ LIST COUNT [PADS]) => (list list)
Returns 2 values, the leading COUNT elements from LIST as a new list, and the remaining elements from LIST. Should there be fewer than COUNT elements available padding is attempted.
Padding is performed by trying to complete the remaining elements from the list PADS.
COUNT is a natural fixnum. PADS is a list or #f. Default is '().
A negative COUNT is treated as 0.
When PADS is #f then an incomplete leading sublist is treated as '(). The very odd treatment of PADS = #f can safely be ignored since this is not the default behavior.
(split-at+ '(1 2 3) 3) ;=> '(1 2 3) '() (split-at+ '(1 2 3) 2) ;=> '(1 2) '(3) (split-at+ '(1 2 3) 4) ;=> '(1 2 3) '() (split-at+ '(1 2 3) 4 #f) ;=> '() '()
section[procedure] (section LIST SIZE [[STEP] PADS]) => list
Returns a list of list, built by taking SIZE elements from LIST every STEP elements. When too few elements remain to complete a section padding is performed.
SIZE is a positive fixnum. STEP is a positive fixnum. Default is SIZE. PADS is a list or #f. Default is '().
When PADS is #f then any incomplete trailing section is dropped. The very odd treatment of PADS = #f can safely be ignored since this is not the default behavior.
(section '(1 2) 3 3 '(3 4 5)) ;=> ((1 2 3)) (section '(1 2 3) 2 1 '(3 4 5)) ;=> ((1 2) (2 3)) (section '(1 2 3) 2 2 '(4 5)) ;=> ((1 2) (3 4)) (section '(1 2 3) 2 2) ;=> ((1 2) (3))
length=0?[syntax] (length=0? LIST) => boolean
List of length zero? (Just null?.)
length=1?[syntax] (length=1? LIST) => boolean
List of length one?
length>1?[syntax] (length>1? LIST) => boolean
List of length greater than one?
length=2?[syntax] (length=2? LIST) => boolean
List of length two?
ensure-list[syntax] (ensure-list OBJECT) => list
Returns a list, either the list OBJECT or (list OBJECT).
not-null?[syntax] (not-null? LIST) => (or list boolean)
Returns #f if the given LIST is empty, and LIST otherwise.
alist-delete-first[syntax] (alist-delete-first KEY ALIST [TEST?])
Returns (alist-delete/count KEY ALIST [TEST?] 1).
alist-delete-first![syntax] (alist-delete-first! KEY ALIST [TEST?])
Destructive version of alist-delete-first.
assoc-def[syntax] (assoc-def KEY ALIST [TEST] [NOT-FOUND])
The assoc procedure with an optional test and default value.
assv-def[syntax] (assv-def KEY ALIST [NOT-FOUND])
The assv procedure with a default value.
assq-def[syntax] (assq-def KEY ALIST [NOT-FOUND])
The assq procedure with a default value.
alist-inverse-ref[procedure] (alist-inverse-ref VALUE ALIST [TEST? [NOT-FOUND]])
Returns the first key associated with VALUE in the ALIST using the TEST? predicate, else NOT-FOUND.
TEST? is eqv? and NOT-FOUND is #f.
alist-delete/count[procedure] (alist-delete/count KEY ALIST [TEST? [COUNT]])
Deletes the first COUNT associations from alist ALIST with the given key KEY, using key-comparison procedure TEST?. The dynamic order in which the various applications of equality are made is from the alist head to the tail.
Returns a new alist. The alist is not disordered - elements that appear in the result alist occur in the same order as they occur in the argument alist.
The equality procedure is used to compare the element keys, key[i: 0 <= i < (length ALIST)', of the alist's entries to the key parameter in this way: (TEST? KEY key[i]).
COUNT defaults to essentially, infinity, and EQUALITY? defaults to eqv?.
alist-delete!/count[procedure] (alist-delete!/count KEY ALIST [TEST? [COUNT]])
Destructive version of alist-delete/count.
alist-delete-first and alist-delete-first! are also available as procedures.
unzip-alist[procedure] (unzip-alist ALIST)
Returns 2 values, a list of the keys & a list of the values from the ALIST.
zip-alist[procedure] (zip-alist KEYS VALUES)
Returns an association list with elements from the corresponding items of KEYS and VALUES.
Error signaling versions of the standard association lookup functions. When the KEY is not found and a NOT-FOUND value is not supplied an error is invoked.
plist->alist[procedure] (plist->alist PLIST) => list
Returns the association-list form of PLIST.
alist->plist[procedure] (alist->plist ALIST) => list
Returns the property-list form of ALIST.
shift![procedure] (shift! LIST [DEFAULT]) => *
Retrns the first element of LIST, or DEFAULT when LIST is null.
The car and cdr of the first pair of LIST are set to the corresponding element of the second pair.
Like a stack-pop.
unshift![procedure] (unshift! OBJECT LIST) => list
The car of the first pair of LIST is set to OBJECT. The cdr of the first pair of LIST is set to LIST.
Like a stack-push.
shift!/set[syntax] (shift!/set VARIABLE [WHEN-EMPTY])
Like shift! but assigns the VARIABLE '() after shifting from a list of length 1.
WHEN-EMPTY, which defaults to #f, is returned when the list bound to VARIABLE is empty.
andmap[procedure] (andmap FUNC LIST...) => boolean
The arity of the function FUNC must be the length of LIST....
(and (FUNC (car LIST)...) (andmap FUNC (cdr LIST)...)).
ormap[procedure] (ormap FUNC LIST...) => boolean
The arity of the function FUNC must be the length of LIST....
(or (FUNC (car LIST)...) (ormap FUNC (cdr LIST)...)).
Bugs and Limitations
- Added skip+, split-at+, and section.
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