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Re: seq-some-p and nil

From: Nicolas Petton
Subject: Re: seq-some-p and nil
Date: Mon, 07 Sep 2015 22:44:42 +0200
User-agent: Notmuch/0.19 (http://notmuchmail.org) Emacs/ (x86_64-unknown-linux-gnu)

Stefan Monnier <address@hidden> writes:

>>> If the function is not supposed to return non-nil if an element is
>>> matched but the element itself, then would it be ok? OTOH there would be
>>> again no way to differentiate between no element found and nil being
>>> found in the sequence.
> Returning what FUN returned seems like a better choice.
> If you need the element matched, then you can simply arrange for FUN
> to return the element.

There is a misunderstanding here I think.

The way I see it, they are two different functions: the (new) seq-some,
and this other function that is now missing in seq, with the new
implementation of `seq-some'.

This new function would be used to find an element in a seq using a
predicate.  CL has `find-if,' Scheme has `find', Clojure has `some',
Smalltalk has `detect:', etc.

Also, both the CL and scheme versions have the nil value ambiguity, but
since these functions are not supposed to return the logical truth on a
match, it is in my opinion fine.

I think I could name this function `seq-find'.

Nicolas Petton

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