http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51540
--- Comment #12 from Christopher Yeleighton <giecrilj at stegny dot 2a.pl> 2011-12-16 18:59:31 UTC --- Additionally, and also for the default operator form, it is unclear what the result is when the operator is noncommutative. That is, whether y[n+1] is set to x[n+1]+y[n] or y[n]+x[n+1], or if the order is somewhat random altogether (which would make partial_sum unusable as a potential driver for the equation y[n+1]=f(y[n])).