How to compile apps with g77 on OS X Lion? I am running Mac OS X 10.7.3 (Lion)

I have a problem in using the fortran compiler g77: any program I try to compile, it gives me this message: "g77: installation problem, cannot exec `as"

I've downloaded and installed the latest release of Xcode, but nothing changed...

Thanks in advance for any help,

Marco
g77 is not part of Xcode. You may have a look here http://hpc.sourceforge.net/ which provides a version compatible with Lion and XCode 4.x. 


  On LION, with XCode 4.3 you will need to download the command-line tools as an additional step. You will find the option to download the command-line tools in XCode 4.3's Preferences