Re: Changing the way bash expands associative array subscripts

[Alex fxmbsw7 Ratchev]

hello, excuse my bad english
your sample code that you write what it should produce you propose for the
future so ?

it doesnt make me much sense that unset -v assoc[$key] gives syntax error
or so..

also about the assoc_expand_once i dont understand
cant it be as written, expand_once ( maybe _at_beginning_only )

set unset -v assoc[$key]  would expand key as alike the first argument of
[[ comparision
to a string $( echo foo ) .. no more further .. .. and work out .. .. ?

i dont understand im sorry

On Tue, Mar 16, 2021 at 7:03 AM Lawrence Velázquez <vq@larryv.me> wrote:

> > On Mar 15, 2021, at 9:03 PM, Léa Gris <lea.gris@noiraude.net> wrote:
> >
> > Please excuse my profanity of mentioning zsh in this list, but I really
> think features and behavior convergence can benefit end users in multiple
> ways, especially when expanding beyond the POSIX sh scope.
> >
> > What direction has taken zsh with expanding associative array indexes?
>
> Broadly speaking, zsh treats subscript expressions as if they are
> double-quoted, but it does not perform arithmetic expansion on associative
> array indices (although subscript expressions must still adhere to related
> parsing rules).
>
>         % zsh --version; echo
>         zsh 5.8 (x86_64-apple-darwin18.7.0)
>
>         % cat /tmp/demo1
>         # Chet's example modified to highlight certain behaviors
>         foo() {
>             echo uname >&2
>             echo +1
>         }
>
>         declare -A assoc
>         key='x$(foo)]=1,b[1$(foo)'
>
>         assoc[$key]=0
>         declare -p assoc b
>
>         % zsh -f /tmp/demo1
>         /tmp/demo1:declare:10: no such variable: b
>         typeset -A assoc=( ['x$(foo)]=1,b[1$(foo)']=0 )
>
> However, it does perform multiple expansions in arithmetic contexts.
>
>         % cat /tmp/demo2
>         # Chet's example modified to highlight certain behaviors
>         foo() {
>             echo uname >&2
>             echo +1
>         }
>
>         declare -A assoc
>         key='x$(foo)]=1,b[1$(foo)'
>
>         (( assoc[$key]++ ))
>         declare -p assoc b
>
>         % zsh -f /tmp/demo2
>         uname
>         uname
>         typeset -A assoc=( [x+1]=1 )
>         typeset -a b=( '' 1 )
>
> Furthermore, "as if they are double-quoted" is rather literal. (Special
> handling allows the use of a["foo"] instead of a[\"foo\"].)
>
>         % cat /tmp/demo3
>         declare -A a
>         key='$(echo foo)'
>         a[$key]=1
>         a['$key']=2
>         a["foo"]=3
>
>         declare -p a
>
>         % zsh -f /tmp/demo3
>         typeset -A a=( ['"foo"']=3 ['$(echo foo)']=1 [\''$(echo foo)'\']=2
> )
>
> If we tweak the preamble to create the intended array (and disable NOMATCH
> to treat failed filename generation as bash does), the unset commands work
> the same as in Chet's proposal.
>
>         % cat /tmp/demo4
>         declare -A a
>         key='$(echo foo)'
>         a[$key]=1
>         a[\$key]=2
>         a[foo]=3
>
>         # Avoid Chet's intentional error because it's difficult to get zsh
> to
>         # imitate it faithfully.
>         #unset -v a[$key]
>         declare -p a
>
>         # unsets element with key $key
>         unset -v a['$key']
>         declare -p a
>
>         # unsets element with key $(echo foo)
>         unset -v a["$key"]
>         declare -p a
>
>         # unsets element with key foo
>         eval unset -v a\["$key"\]
>         declare -p a
>
>         % zsh -f +o NOMATCH /tmp/demo4
>         typeset -A a=( ['$(echo foo)']=1 ['$key']=2 [foo]=3 )
>         typeset -A a=( ['$(echo foo)']=1 [foo]=3 )
>         typeset -A a=( [foo]=3 )
>         typeset -A a=( )
>
> vq
>