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Date: Sun,  4 Oct 2009 18:59:59 +0800
Message-ID: <140e7ec30910040359q28c30ea2re5185846042cf43a@mail.gmail.com>
From: sqweek <sqweek@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] mishandling empty lists - let's fix it
Topicbox-Message-UUID: 7d3b4394-ead5-11e9-9d60-3106f5b1d025

2009/10/4 Sam Watkins <sam@nipl.net>:
> I wrote:
>> I don't see how this can be fixed in unix without breaking umpteen milli=
on
>> shell scripts.
>
> On Sun, Oct 04, 2009 at 06:12:15AM +0200, lucio@proxima.alt.za wrote:
>> By creating new commands with distinct new names.
>
> I thought of a better way. =C2=A0We can fix the commands without breaking
> compatibility, using `--'. =C2=A0`--' in unix normally excludes further o=
ptions.

 It seems to me the obvious way to gain consistency is to do the list
parsing in one place only:

fn apply {
    cmd=3D$1
    shift
    while(! test $1 =3D :) {
        cmd=3D($cmd $1)
        shift
    }
    for(i in $*) $cmd <$i
}
# eg: apply grep foo : *.c

 Of course, this is likely to run you into other problems with the way
some programs want to use their arguments, which is why unix/plan 9
adopt the pragmatic approach.

 PS. excuse the test usage, feel free to point out the ~ idioms - if I
see them often enough they might stick in my memory :)
 PPS. i didn't actually check the semantics of for on an empty list,
maybe a conditional is required

-sqweek