Re: [BUG] POSIX arith: inf, nan should be variables

[Oliver Kiddle <opk@zsh.org>]

Martijn Dekker wrote:
> $ zsh --emulate sh -c 'inf=1; nan=2; echo $((inf)) $((nan))'
> Inf NaN
>
> Expected: 1 2

> So, what shell option to tie that to? That's a bit difficult. It needs 

The closest comparable feature is the decision in params.c as to whether
it should setup other special variables that aren't in the standard.

That seems to only check something like !EMULATION(EMULATE_SH) rather
than an actual option. Much of that has to run before zsh has got as far
as sourcing dot files that might setup options so it likely never made
sense to create an option for it. Most uses of directly checking
emulation state seem to be in initialisation code.

I wouldn't rename an option for compatibility. And while OCTAL_ZEROES is
similar in controlling interpretation of numbers in math mode it differs
in that it enables a potentially problematic standard feature while
Inf/NaN are a zsh extension. So I wouldn't view preferences on them as
being intrinsically linked.

Oliver