I would have expected maxima to know exponential integral diverges.

Hi,

I would have expected Maxima to know that the following integral
diverges for negative a, but apparently it doesn't:

(%i1) ein: 'integrate(exp(-a*x)/x,x,1,inf);
                                 inf
                                /      - a x
                                [    %e
(%o1)                           I    ------- dx
                                ]       x
                                /
                                 1
(%i2) ev(ein,nouns);
Is  a  positive, negative, or zero?

positive;
(%o2)                       gamma_incomplete(0, a)
(%i3) ev(ein,nouns);
Is  a  positive, negative, or zero?

negative;
                                 inf
                                /      - a x
                                [    %e
(%o3)                           I    ------- dx
                                ]       x
                                /
                                 1
(%i4) ev(ein,nouns);
Is  a  positive, negative, or zero?

zero;
defint: integral is divergent.
 -- an error. To debug this try: debugmode(true);

Bernard