Path: utzoo!attcan2!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!mandrill!gatech!hubcap!mcvax!cernvax!hjm From: mcvax!cernvax!hjm@uunet.UU.NET (hjm) Newsgroups: comp.parallel Subject: Re: parallel numerical algorithms Message-ID: <1797@hubcap.UUCP> Date: 1 Jun 88 20:26:58 GMT Sender: fpst@hubcap.UUCP Lines: 20 Approved: parallel@hubcap.clemson.edu In article <1772@hubcap.UUCP> noao!mcdsun!asuvax!asuvax!nelan@HANDIES.UCAR.EDU (George Nelan) writes: > >I guess no side-effects => purely functional programs, huh? > There is one major problem with this: no side-effects => no I/O, which is a fairly useful side-effect of most computation. This is not strictly true, but for the sequential type of I/O that we're all accustomed to doing there is state transmitted between statements in terms of the I/O being performed. For example, a function such as read_next_input_value(stdin) will return different things on different calls, and so is strictly not a function. OK, a bodge can be performed so that a state variable is added so that referential transparency is preserved, but just try passing the entire filing system of your machine as an argument to every function that does anything to any file! Do that and we'llall need a massively parallel machine just for word processing. Having said all that, I like functional languages, especially since they can be implemented in parallel cleanly. It's just a pity that the machine has to talk to the outside world ... Hubert Matthews