how to write Build-depends argument for gfortran

[kamaraju kusumanchi <raju.mailinglists@gmail.com>]

Hi
  My apologies if this is a newbie question. I searched in google for a 
while and could not find an answer to this.

I want to build debian package for a library called fortranposix. The 
upstream source can be found at

http://sourceforge.net/projects/fortranposix

This library depends on some kind of fortran 90 compiler being installed 
on the system. gfortran is the Fortran 90 compiler available in latest 
versions of gcc. Currently gfortran is available (on sid atleast) only 
through gcc-snapshot. However the description of gcc-snapshot 
specifically asks not to build packages against it.

So now my questions are

1) How can I make sure that the user has gfortran installed on his system.

2) From reading 
http://www.debian.org/doc/manuals/maint-guide/ch-dreq.en.html , I know 
that only package names can be listed as arguments to Build-Depends 
command. Is there any way I can list binary name (gfortran) instead of 
package name (gcc-snapshot) as dependency?

Making dependency against gfortran has also the advantage that it works 
even if the user has compiled it by himself instead of going through the 
gcc-snapshot way.

Any solutions/work arounds are appreciated. At present, I would be happy 
if the solution works for sid. But if the solution is good for sarge 
then it is even better.

thanks in advance
raju