On Thu, 14 May 2015, luigi scarso wrote:

On Thu, May 14, 2015 at 5:45 PM, Aditya Mahajan <adityam@umich.edu> wrote:

On Thu, 14 May 2015, Mojca Miklavec wrote:

 Hi,

I suspect that the equation numbering in attachment
(eq-with-chapter.png) is wrong. Shouldnt't the number be positioned on
the right (not on the left)? And in case that this positioning on the
left is intentional: is there any way or setting to force the equation
number to be moved to the right?

This is a bug in luatex:

http://tracker.luatex.org/view.php?id=807

Aditya

isn't the the formula  simply too long ?

Yes. In tex and pdftex, when the formula is too long \eqno is placed on the next line, shifted to the right. In luatex, the equation number is not shifted.

Compare the output of

\hsize=2cm
$$a^2+b^2=c^2\eqno(1)$$
\bye

for pdftex and luatex.