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Ingy döt Net 2026-02-01 16:33:20 -08:00
parent 5150844a7d
commit 4bb20c9b71
7735 changed files with 38060 additions and 199180 deletions
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26
Task/Search-a-list/Emacs-Lisp/search-a-list.l
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(defun get-index (item list)
"Return index of first ITEM in LIST.
Display error message if ITEM is not
part of LIST."
(if (seq-position list item) ; if it's in LIST
(seq-position list item) ; return index
;; else, provide an error message
(message "%s is not an element in %s." item list)))
;; My thanks to Protesileos Stavrou (aka "Prot") for
;; key ideas for the section below, including reversing
;; the list in order to easily find the last item in it.
(defun last-position (item list)
"Return last ITEM index in LIST."
;; test if ITEM is in LIST
(if (seq-position list item) ; if it's in LIST
(progn
;; subtract the adjusted length of the list from
;; the position of ITEM in the reverse of LIST
(-
;; 1- corrects for length being 1 based, but seq-position is 0 based
(1- (length list))
;; reverse list because
;; seq-position searches from beginning of list
(seq-position (nreverse list) item)))
(message "%s is not an element in %s." item list)))