add a toplevel "dir" or "ls" command

[bvanevery]

The toplevel currently has "cd" and "pwd" commands. It is fairly natural when navigating a file system hierarchy, to look at the contents of a directory to figure out where to navigate to next. A simple "dir" or "ls" command that lists the contents of the directory, and whether items are files or folders that one can "cd" to, would be convenient. Otherwise one must maintain a separate OS window to do the navigation, and one must "double type" any pathnames to keep things in synch. It is less convenient.

Such a command would be good for a non-Lisp user's first impressions of CCL.

[rme]

Common Lisp includes a function called DIRECTORY, which will list files that match a given pathname. It does not work exactly like "ls" or "dir", and that often confuses people.

 http://ccl.clozure.com/ccl-documentation.html#Directory documents CCL's extensions to CL:DIRECTORY.

I can imagine implementing more toplevel commands to make shell-like functionality available, but users typically run the lisp in emacs or some other environment that makes it easy to copy and paste text, and provide more sophisticated interaction support generally.