Hi Andrew,

Interesting point. 

> On 23 Sep 2015, at 09:49, Andrew Parsloe <[log in to unmask]> wrote:
> 
> \int_eval:n { - (1+2) }
> 
> gives a "Missing number, treated as zero" message. So does \int_eval:n { + (1+2) }. But
> 
> \int_eval:n { 0 - (1+2) }

From memory \numexpr chains +ve and -ve signs appropriately... I'm not sure if it's a good idea but I wonder if prepending "0+" to every <int expr> would work to make this interface a bit more general without adding too much overhead.

Will
(Sent from phone; please excuse brevity.)