selecting elements in array

selecting elements in array

[Wataru Kagawa]

Hi all,

How do I select elements with indices that are multiples of 3, in an 
array?  For example, I have,

list=( 123 native Terminal 456 native Excel 789 native X11 )

and would like to select,

Terminal Excel X11

for compadd.  Help is much appreciated.

Wataru Kagawa

Re: selecting elements in array

[Eric Mangold]

On Thu, 21 Apr 2005 13:43:55 +1000, Wataru Kagawa  
<wkagawa@jota.gsc.riken.go.jp> wrote:

> Hi all,
>
> How do I select elements with indices that are multiples of 3, in an  
> array?  For example, I have,
>
> list=( 123 native Terminal 456 native Excel 789 native X11 )
>
> and would like to select,
>
> Terminal Excel X11

for i in {1..3}; do
print $list[$(($i*3))]
done

or build a new array:

new=()
for i in {1..3}; do
new+=( $list[$(($i*3))] )
done

-Eric

>
> for compadd.  Help is much appreciated.
>
> Wataru Kagawa
>

Re: selecting elements in array

[Bart Schaefer]

On Apr 21,  4:06pm, Eric Mangold wrote:
} Subject: Re: selecting elements in array
}
} On Thu, 21 Apr 2005 13:43:55 +1000, Wataru Kagawa  
} <wkagawa@jota.gsc.riken.go.jp> wrote:
} 
} > How do I select elements with indices that are multiples of 3, in an  
} > array?  [...] for compadd.  Help is much appreciated.
} 
} for i in {1..3}; do
} print $list[$(($i*3))]
} done

Right, except replace "print" with "compadd", and you don't need the
$(( )) because the stuff in the [ ] is already treated as arithmetic.

    for i in {1..3}; do compadd $list[i*3]; done
or
    for ((i=3; $+list[i]; i+=3)); do compadd $list[i]; done

or any of a number of other ways.  There's not, however, a way to write
a single subscript parameter expansion that picks out non-contiguous
array slices.