Re: [Help-bash] opposite of 'shift'

[Peng Yu]

On Thu, Feb 16, 2012 at 12:52 AM, Pierre Gaston <address@hidden> wrote:
>
>
> On Thu, Feb 16, 2012 at 8:47 AM, Peng Yu <address@hidden> wrote:
>>
>> Hi,
>>
>> I'm wondering what is the opposite of 'shift'. I'm trying to look for
>> something like 'push', 'push_front', etc. But I don't find it. Is
>> there something in bash that do push to the front of an array (and to
>> "$@" by default)?
>>
>
> There's no opposite only:
> set -- blah "$@"

I recall now that I have seen this before. I think that it is probably
better to have some function like 'unshift' to make operation
symmetric. Many other languages have symmetric functions. Bash
probably should be improved in these aspects. For example, in perl, it
has the following (see
http://www.cs.cmu.edu/afs/cs/usr/rgs/mosaic/pl-exp-arr.html)


shift
    Shifts the first value of the array off and returns it, shortening
the array by 1 and moving everything down. If there are no elements in
the array, returns the undefined value. If ARRAY is omitted, shifts
the @ARGV array in the main program, and the @_ array in subroutines.
(This is determined lexically.) See also unshift(), push() and pop().
Shift() and unshift() do the same thing to the left end of an array
that push() and pop() do to the right end.

> It's probably a better idea to implement whatever structure you want with an
> array



-- 
Regards,
Peng