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| author | Kaz Kylheku <kaz@kylheku.com> | 2015-10-05 06:20:08 -0700 |
|---|---|---|
| committer | Kaz Kylheku <kaz@kylheku.com> | 2015-10-05 06:20:08 -0700 |
| commit | 7f7379793f4732b09350798c22d9ed22dd2f11ba (patch) | |
| tree | de85d0c9cf8927395b3bb64b38272b261d6a8c4a /txr.1 | |
| parent | c17054aa390ce42e867d9ce7b5fd821e0c666d45 (diff) | |
| download | txr-7f7379793f4732b09350798c22d9ed22dd2f11ba.tar.gz txr-7f7379793f4732b09350798c22d9ed22dd2f11ba.tar.bz2 txr-7f7379793f4732b09350798c22d9ed22dd2f11ba.zip | |
New functions take, drop, {take,drop}-{while,until}.
* lib.c (take_list_fun, take_while_list_fun,
take_until_list_fun): New static functions.
(take, take_while, take_until, drop, drop_while,
drop_until): New functions.
* eval.c (eval_init): Register intrinsics take,
take-while, take-until, drop, drop-while, drop-until.
* txr.1: Documented.
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 181 |
1 files changed, 181 insertions, 0 deletions
@@ -19167,6 +19167,187 @@ is a list, then must be monotonically increasing. +.coNP Function @ take +.synb +.mets (take < count << sequence ) +.syne +.desc +The +.code take +function returns +.meta sequence +with all except the first +.meta count +items removed. + +If +.meta sequence +is a list, then +.code take +returns a lazy list which produces the first +.meta count +items of sequence. + +For other kinds of sequences, including lazy strings, +.code drop +works eagerly. + +If +.meta count +exceeds the length of +.meta sequence +then a sequence is returned which has all the items. +This object may be +.meta sequence +itself, or a copy. + +If +.meta count +is negative, it is treated as zero. + +.coNP Functions @ take-while and @ take-until +.synb +.mets (take-while < predfun < sequence <> [ keyfun ]) +.mets (take-until < predfun < sequence <> [ keyfun ]) +.syne +.desc +The +.code take-while +and +.code take-until +functions return a prefix of +.meta sequence +whose items satisfy certain conditions. + +The +.code take-while +function returns the longest prefix of +.meta sequence +whose elements, accessed through +.meta keyfun +satisfy the function +.metn predfun . + +The +.meta keyfun +argument defaults to the identity function: the elements +of +.meta sequence +are examined themselves. + +The +.code take-until +function returns the longest prefix of +.meta sequence +which consists of elements, accessed through +.metn keyfun , +that do +.B not +satisfy +.meta predfun +followed by an element which does satisfy +.metn predfun . +If +.meta sequence +has no such prefix, then an empty sequence +is returned of the same kind as +.metn sequence . + +If +.meta sequence +is a list, then these functions return a lazy list. + +.coNP Function @ drop +.synb +.mets (drop < count << sequence ) +.syne +.desc +The +.code drop +function returns +.meta sequence +with the first +.meta count +items removed. + +If +.meta count +is negative, it is treated as zero. + +If +.meta count +is zero, then +.meta sequence +is returned. + +If +.meta count +exceeds the length of +.meta sequence +then an empty sequence is returned +of the same kind as +.metn sequence . + +.coNP Functions @ drop-while and @ drop-until +.synb +.mets (drop-while < predfun < sequence <> [ keyfun ]) +.mets (drop-until < predfun < sequence <> [ keyfun ]) +.syne +.desc +The +.code drop-while +and +.code drop-until +functions return +.meta sequence +with a prefix of that sequence removed, +according to conditions involving +.meta predfun +and +.metn keyfun . + + +The +.code drop-while +function removes the longest prefix of +.meta sequence +whose elements, accessed through +.meta keyfun +satisfy the function +.metn predfun , +and returns the remaining sequence. + +The +.meta keyfun +argument defaults to the identity function: the elements +of +.meta sequence +are examined themselves. + +The +.code drop-until +function removes the longest prefix of +.meta sequence +which consists of elements, accessed through +.metn keyfun , +that do +.B not +satisfy +.meta predfun +followed by an element which does satisfy +.metn predfun . +A sequence of the remaining elements is +returned. + +If +.meta sequence +has no such prefix, then a sequence +same as +.meta sequence +is returned, which may be +.meta sequence +itself or a copy. + .coNP Function @ search .synb .mets (search < haystack < needle >> [ testfun <> [ keyfun ]) |