Numbers with leading _

Numbers with leading _

[Mikael Magnusson]

I was playing with extending hasbraces+xpandbraces to allow _ in
numbers via zstrtoul_underscore, and noticed that in normal math
context, this happens:
% echo $(( _1000 ))
0
% a=(1 2 3); echo $a[_1]

% a=(1 2 3); echo $a[1_]
1

but my modifications worked fine:
% echo {_999_.._1_0_0_1_}
999 1000 1001

Obviously there's no real reason why anyone should want to specify a
number with a leading underscore but is there a reason to reject it in
the normal math context, and should we print some kind of error when
we do it rather than silently parse it as a 0?

I didn't yet try to track down where this rejection happens, but it's
at least not in zstrtoul_underscore.

-- 
Mikael Magnusson

Re: Numbers with leading _

[Peter Stephenson]

> On 21/11/2022 16:22 Mikael Magnusson <mikachu@gmail.com> wrote:
> I was playing with extending hasbraces+xpandbraces to allow _ in
> numbers via zstrtoul_underscore, and noticed that in normal math
> context, this happens:
> % echo $(( _1000 ))
> 0
> % a=(1 2 3); echo $a[_1]
> 

That's a reference to the variable $_1 (which obviously isn't set).

pws

Re: Numbers with leading _

[Mikael Magnusson]

On 11/21/22, Peter Stephenson <p.w.stephenson@ntlworld.com> wrote:
>> On 21/11/2022 16:22 Mikael Magnusson <mikachu@gmail.com> wrote:
>> I was playing with extending hasbraces+xpandbraces to allow _ in
>> numbers via zstrtoul_underscore, and noticed that in normal math
>> context, this happens:
>> % echo $(( _1000 ))
>> 0
>> % a=(1 2 3); echo $a[_1]
>>
>
> That's a reference to the variable $_1 (which obviously isn't set).

Aha, that indeed does make sense now, thanks.
% _1000=5
% echo $(( _1000 ))
5

-- 
Mikael Magnusson