Integral of expm function

[Montgomery-Smith, Stephen]

In a post on the octave-maintainers mailing list, someone referenced this:

http://slicot.org/objects/software/shared/doc/MB05ND.html

It includes a function that computes

H(t,A) = integral_0^t expm(s*A) ds

Is there an octave function that computes H?  This would be useful for
me.  I did consider using

inv(A) * expm(t*A)

but my matrix A happens to be singular.