From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 In-Reply-To: References: <81c18ae059da79eb550d650650fa88c4@india.com> Date: Tue, 25 Nov 2014 10:00:22 +0000 Message-ID: From: Charles Forsyth To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> Content-Type: multipart/alternative; boundary=f46d0438948fb8a8760508abfaa1 Subject: Re: [9fans] rc: null list in concatenation Topicbox-Message-UUID: 2e17db84-ead9-11e9-9d60-3106f5b1d025 --f46d0438948fb8a8760508abfaa1 Content-Type: text/plain; charset=UTF-8 It's a "null list" not a "null string". You can use a null string: % s='' % ls $s^/x but not a null list (like using null in many lisp list operations, or the difference between strcat of nil and strcat of ""): % s=() % ls $s^/x rc (-/bin/rc): null list in concatenation A completely unset variable is a null list. Also, `{...} returns a list (of words) not a string, hence the diagnostic in that case. --f46d0438948fb8a8760508abfaa1 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
It's a "null list"= ; not a "null string". You can use a null string:

% s=3D''
% ls $s^/x

but not a null list (like using null i= n many lisp list operations, or the difference between strcat of nil and st= rcat of ""):

% s=3D()
% ls $s^/x
rc (-/bin/rc): null li= st in concatenation

A completely unset variable is a null list. Also, `{...} retu= rns =C2=A0a list (of words) not a string,
h= ence the diagnostic in that case.

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