Re: fast subshell

[Ray Andrews <rayandrews@eastlink.ca>]

On 01/04/18 11:39 AM, Bart Schaefer wrote:
>
> It's quite possible that doing the memory management for the
> assignment to all_matches in a newly forked process is faster than in
> the original shell (perhaps because the subshell never needs to free
> it again?).  There is also some overhead involved in saving/restoring
> IFS with "local" which you are avoiding.
It's rather interesting.  I suppose the deepest gurus could actually 
discuss the nuts and bolts in detail.  Meanwhile my fears of some 
dreadful overhead are dead.
>
> Also there's really no reason to do both "local IFS=..." and
> "IFS=$OLD_IFS"
I need the thing restored for use latter in the same function. I've 
since seen that:

(
IFS=...
...
)

Somehow screws up, I'm not sure why but it has effects outside the 
parenthesis.  Issues with a subshell within a subshell?  Don't seem right.
>    (){ local IFS=$'\n'; all_matches=( $( whence -mavS $@ ) ) }
I'll try that.
> Or you can do it without changing IFS at all, like this:
>
>    all_matches=( ${(f)"$( whence -mavS $@ )"} )
>
Now that's the 'real' answer.  Direct control within the statement 
itself.   Gotta get used to these nested parameters, it's not really 
that scary.