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delete-if-not 170
If the value of the :from-end argument is non-nil, it only affects the result
when the :count argument is specified. In that case only the rightmost
:count elements that satisfy the predicate are deleted.
For example:
(delete-if #'numberp '(4 2 4 1) :count 1 ) => (2 4 1)
(delete-if #'numberp '(4 2 4 1) :count 1 :from-end t) => (4 2 4)
Use the keyword arguments :start and :end to delimit the portion of the
sequence to be operated on.
:start and :end must be non-negative integer indices into the sequence.
:start must be less than or equal to :end, else an error is signalled. It
defaults to zero (the start of the sequence).
:start indicates the start position for the operation within the sequence.
:end indicates the position of the first element in the sequence beyond the
end of the operation. It defaults to nil (the length of the sequence).
If both :start and :end are omitted, the entire sequence is processed by
default.
For example:
(delete-if #'atom 'e'a 1 "list")) => ('A)
I
(delete-if #'numberp '(4 1 4) :start 1 :end 2) => (4 4)
(delete-if #'evenp '(4 1 4) :start 0 :end 3) => (1)
The :count argument, if supplied, limits the number of elements deleted.
If more than :count elements of sequence satisfy the predicate, then only
the leftmost :count of those elements are deleted.
For example:
(del ete-i f #' oddp I (1 1 2 2) : count 1 ) => (1 2 2)
delete-if is the destructive version of remove-if.
For a table of related items: See the section "Sequence Modification" in
Symbolics Common Lisp: Language Concepts.
delete-if-not predicate sequence &key key from-end (start 0) end Function
count
delete-if-not returns a sequence of those items in the subsequence of sequence
delimited by :start and :end which do not satisfy predicate. The
elements that are not deleted occur in the same order in the result that
they did in the argument. This is a destructive operation. The argument