The Fast Scala Compiler, fsc, is one of the components of the standard Scala distribution. It is equivalent in terms of functionality to the standard Scala compiler, but it keeps the actual compilation module loaded in memory so that subsequent invocations do not need to initialize the compiler again, and are therefore faster.
The communication between the fsc command and the resident compiler takes place by using a network connection. On Macintosh OS X computers, the firewall may interfere with this communication, causing unexpected errors when calling fsc. If you encounter problems of this kind, just follow the guide below, in order to configure the OS X firewall.
It is necessary to use the exception list in order to allow specific programs to pass the firewall. Both the fsc and scala binaries have to be allowed to receive incoming connections. Here's a step-by-step guide:
$ open /opt/local/share/scala/bin
This guide was contributed by user "exty".