Re: status on $[arith] for eval arith vsl $((arith))??

[Maarten Billemont]

On 08 Apr 2012, at 01:47, Chet Ramey wrote:
> On 4/7/12 4:45 PM, Linda Walsh wrote:
>> 
>> 
>> 
>> In modifying some released code on my distro,    I ran into the extensive use
>> of   $[arith]  as a means for returning arithmetic evaluations of the
>> expression.
>> 
>> I vaguely remember something like that from years ago, but never see any
>> reference to
>> it -- yet it works, and old code seems to rely on it -- and
>> "$[(1+2)/3]"  looks cleaner than "$(((1+2)/3))".  So what's up with that?
> 
> It dates from Posix circa 1990 (1003.2d9, of which I've lost my paper
> copy).  I implemented it after the Berkeley guys, mostly Marc
> Teitelbaum, put it into Posix.  It ended up getting dropped in favor
> of the ksh $((...)) expansion, at which point everyone deprecated the
> old $[...].  I removed it from the manual sometime later, but it still
> works as it always has.
> 
> Chet


Any particular reason for not removing old undocumented functionality, or is 
that mostly the nature of this beast - dragging along and maintaining ancient 
code for the sake of compatibility?

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