# [PURRS-devel] Re: Problem with CoStLy 0.2

Roberto Bagnara bagnara at cs.unipr.it
Tue Nov 19 16:03:44 CET 2002

```Markus Neher wrote:
> thank you for your email. We'll check the problem and will hopefully
> find a solution to it.

Thanks a lot.  We are indeed stuck at this and we do not know how we
should proceed.  We have written a temporary workaround for the problem
but we are unsure whether this is the way to go.  In fact, new cases are
arising: for instance, squaring a negative real interval causes
the function_undefined() exception to be thrown:

(gdb) frame 4
#4  0x080a20e9 in ln(cinterval const&) (z=@0xbfffeba0)
at /home/roberto/purrs/purrs/CoStLy/cimath.cpp:1368
1368          throw function_not_defined();
(gdb) frame 5
#5  0x080ac01b in pow(cinterval const&, cinterval const&) (bas=@0xbfffeba0,
n=@0xbfffea10) at /home/roberto/purrs/purrs/CoStLy/cimath.cpp:2719
2719        return exp(n*ln(bas));
(gdb) print bas
\$5 = (const cinterval &) @0xbfffeba0: {
real_part = {
INF = -0.41421356237309914,
SUP = -0.4142135623730902
},
imag_part = {
INF = 0,
SUP = 0
}
}
(gdb) print n
\$6 = (const cinterval &) @0xbfffea10: {
real_part = {
INF = 2,
SUP = 2
},
imag_part = {
INF = -0,
SUP = -0
}
}
(gdb)

All the best

Roberto

--
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara at cs.unipr.it

```