27_io/istream_extractor_arith.cc fixup

[Gabriel Dos Reis]

Benjamin Kosnik <bkoz@redhat.com> writes:

| > The best fix would be to add some stuff to libmath and get rid of all
| > macro selected regions out of the mainline of code, but I haven't had
| > the time to figure out how to do it yet.
| 
| I agree, this would be the best solution. Perhaps Gaby can help with 
| this?

Certainly, I would like to help fix those non-scalable dependencies on
the C library.

-- Gaby