Op 21-12-18 om 07:53 schreef Bart Schaefer:
> On Thu, Dec 20, 2018 at 2:48 PM Martijn Dekker <martijn@inlv.org> wrote:
>>
>> However, I think having 'set -u' apply to $(( x )) is "obvious" and
>> useful behaviour.
> 
> Reasonable.

This should make that happen, if I did it right. All the regression 
tests pass, including three added ones.

With this patch, zsh throws an error but does not exit on an unset 
variable in the ((arithmetic command)) or in 'let'. But it doesn't exit 
on a syntax error either, so that is consistent. It exits as expected on 
an unset variable in $((arithmetic expansion)).

- M.