2016-02-01 12:04 GMT+01:00 Richard Stallman <rms@gnu.org>:

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>
>   > It makes it harder to catch the bug if you
>   > inadvertently call member with its second
>   > argument not being a sequence ?
>
> There are two ways to look at this:
>
> * Lists should end in nil, and if they don't, functions should complain.
>
> * It is useful generality if functions accept lists that end
> in some other atom.
>
> I don't see that the first is obviously preferable.
>
>
I'm biased by CL I guess.
Then you need 2 functions, one for proper lists and one for improper lists.
But I would call the second one `tree-member' :-)

Greetings,

Fabrice