[Maxima] wrong symbolic sum

[Barton Willis]

-----maxima-bounces at math.utexas.edu wrote: -----

>OK by me to restore sumhack.

Maple 10 defaults to sumhack behavior, I think:

  sum(f(k),k=-9..-13) --> -f(-12) - f(-11) - f(-10)

Currently, we have consistency between things such as

 (%i2) f(n) := block([acc : 0], for i : 0 thru n do acc : acc + i, acc)$
 (%i4) g(n) := sum(i,i,0,n)$

I suppose that's good, but users should expect sums & loops to have
different properties. I might favor making sumhack : true the default.

Barton