Re: [Help-bash] make function local

[Dan Douglas]

On Tue, Apr 7, 2015 at 8:49 PM, Chet Ramey <address@hidden> wrote:
 > Is there a particular problem you're trying to solve for which local
 > functions would be the appropriate solution?

It's occasionally an optimization to eliminate some logic that only needs to be
performed on certain calls. A good (contrived) example might be a directory
traversal function that wants to enable nullglob and dotglob within its body.

     # unoptimized
     function dfs {
         if [[ ! -v localopts ]]; then
             typeset -a localopts
             typeset opt
             for opt in nullglob dotglob; do
                 shopt -q "$opt" || localopts+=("$opt")
             done

             shopt -s "address@hidden"
             dfs "$@"
             shopt -u "address@hidden"
             return
         fi

         typeset file
         for file; do
             if [[ -d $file ]]; then
                 dfs "${file}/"*
             elif [[ -f $file ]]; then
                 # do stuff
             fi
         done
     }

     # A tad better
     function dfs {
         typeset -a localopts
         typeset opt
         for opt in nullglob dotglob; do
             shopt -q "$opt" || localopts+=("$opt”)
         done

         trap “trap RETURN; shopt -u ${localopts[*]}; $(typeset -fp dfs)” RETURN

         function dfs {
             typeset file
             for file; do
                 if [[ -d $file ]]; then
                     dfs "${file}/"*
                 elif [[ -f $file ]]; then
                     # process the file
                 fi
             done
         }

         dfs "$@"
     }

I still vote "no" on this because:
    1. It's doable with a 1-line RETURN trap as above.

    2. If the semantics of nested functions were ever to change, the syntax
    should be reserved for closure support.

    3. Whoever ends up implementing this could have better spent their time
    adding the sorely needed `shopt' option that localizes options so
that scripts
    don't have to. ;-)

-- 
Dan Douglas