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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 43 |
1 files changed, 43 insertions, 0 deletions
@@ -6670,6 +6670,49 @@ The input <list> is unmodified, but the returned list may share substructure with it. If no items are removed, it is possible that the return value is <list> itself. +.SS Function remove-if + +.TP +Syntax: + + (remove-if <predicate-function> <list> : <key-function>) + (keep-if <predicate-function> <list> : <key-function>) + +.TP +Description + +The remove-if function produces a list whose contents are those of +<list> but with those elements removed which satisfy <predicate-function>. +Those elements which are not removed appear in the same order. +The result list may share substructure with the input list, +and may even be the same list object if no items are removed. + +The optional <key-function> specifies how each element from the <list> is +transformed to an argument to <predicate-function>. If this argument is omitted +or specified as nil, then the predicate function is applied to the elements +directly, a behavior which is identical to <key-function> being (fun identity). + +The keep-if function is exactly like remove-if, except the sense of +the predicate is inverted. The function keep-if retains those items +which remove-if will delete, and removes those that remove-if will preserve. + +.TP +Examples: + + ;; remove any element numerically equal to 3. + (remove-if (op = 3) '(1 2 3 4 3.0 5)) -> (1 2 4 5) + + ;; remove those pairs whose first element begins with "abc" + [remove-if (op equal [@1 0..3] "abc") + '(("abcd" 4) ("defg" 5)) + car] + -> (("defg 5)) + + ;; equivalent, without test function + (remove-if (op equal [(car @1) 0..3] "abc") + '(("abcd" 4) ("defg" 5))) + -> (("defg 5)) + .SS Function tree-find .TP |