Hi, all, I am continuing to mess with my little scheme interpreter, and I decided that it would be nice to be able to hit control-C in the middle of a long-running scheme computation to interrupt that and return to the lisp> prompt; hitting control-C and getting back to the shell prompt works, but is a little drastic. So I looked at System.Posix.Signals and after a bit of messing about got the following:
mysighandler = Catch (do hPutStrLn stderr "caught a signal!" fail "Interrupt!")
runREPL :: IO () runREPL = do getProgName >>= writeHdr env <- setupBindings [] True runInit env installHandler sigINT mysighandler Nothing installHandler sigQUIT mysighandler Nothing doREPL env
This compiles just fine, the interpreter runs as usual... but the added code doesn't seem to do anything. You can probably guess already... the print statement in mysighandler is there to see if it actually caught a signal. It does: I see "caught a signal!" just fine, in fact I see dozens of them as I lean on the control-C; but now my scheme calculation doesn't get interrupted at all! I see in the System.Posix.Signals documentation that the signal handler gets invoked in a new thread; is this the source of the problem? If so, what should I do to fix it? I'm afraid that sort of stuff is still beyond my haskell-fu... many thanks! Uwe