REPL Proper Testing

[melsman]

We need to set up proper automatic testing for the REPL, including testing of the various commands and with the basis library loaded...

Also, there are a number of ways in which the REPL can crash (or get into an unfortunate state), including (1) entering the expression Posix.Process.fork() at toplevel, (2) entering the expression OS.FileSys.chDir "..", or (3) reloading an mlb-file after changing some of the source files it refers to. There seem to be no way (in general) to guard against the user doing stupid things like (1) above or by entering(OS.Process.exit 0 : int), or deleting the MLB directory that holds temporary files for the REPL. Problem (2) above we can fix, however. Problem (3) is difficult to solve and we will not make an attempt to solve (3) here, but we will make support for resetting the child process by adding a :reset command. To do something about (3), we first need to detect changes to loaded target code and changes to assumed bases.

Progress:

• Test some basis library functionality.
• Test loading of mlb-file.
• Test type-indexed pretty-printing of boxed and unboxed types.
• Test :set command.
• Add :reset command for respawning the child process.
• Use absolute directories in Repl.c so that OS.FileSys.chDir does not confuse the REPL.