The three programs "ap", "ac", and "af", are somewhat reminiscent
of PC compilers, in that they will compile, edit, compile, edit,
compile, edit, ... ad nauseam, without ever dropping you back to
the shell.  They also (and here is their usefulness) merge your
error messages back into your source file, let you fix your
source, and then remove the messages, all by black magic!  Authored
by Dr. Doom in response to the the "draw a little hand with a finger
pointing to the mistake" syndrome of some popular computers.