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lukego/same.lisp

Created June 1, 2021 09:50
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same.lisp
(defun same (key-fn list &key (test #'eql))
"True if KEY-FN returns the same value for every element of LIST.
Example: (same #'length '((a b c) (d e f) #(1 2 3))) => T"
(or (null list)
(loop with v = (funcall key-fn (first list))
for x in (rest list)
always (funcall test v (funcall key-fn x)))))
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