Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!bfmny0!tneff
From: tneff@bfmny0.UUCP (Tom Neff)
Newsgroups: comp.realtime
Subject: Re: Searching for realtime languages
Message-ID: <14360@bfmny0.UUCP>
Date: 28 May 89 01:28:32 GMT
References: <699@tuvie> <2100@internal.Apple.COM> <14355@bfmny0.UUCP> <9142@csli.Stanford.EDU>
Reply-To: tneff@bfmny0.UUCP (Tom Neff)
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In article <9142@csli.Stanford.EDU> knight@csli.stanford.edu (Bob Knight) writes:
>In article <14355@bfmny0.UUCP> tneff@bfmny0.UUCP (Tom Neff) writes:
>>                                        I recommend PL/M as a realtime
>>language of choice in all Intel CPU environments from 8051 to 80486.
>
>I would agree, having written loads of PL/M code for 808x platforms, with
>one caveat --- if you want/need complex data structures, PL/M is not a good
>choice:  creating an analogue to typedef is painful, one may not nest
>structures, and structures themselves are (grossly, in my opinion) limited
>as to the number of elements they may have.  

Actually as of PL/M 2.7 and later (currently at 3.1 so we're talking a
couple of years) most of those limitations are gone.  Structures can
indeed be nested, and the number of elements is up, as are things like
proc counts and LITERALLY lengths.  A big improvement.  I agree you 
don't have the flexibility of a C typedef, and occasionally it makes
you have to think a bit harder, but my experience in realtime programming
is that anytime things get more complex than what PL/M easily provides,
you SHOULD be thinking harder!  Like whether things need to be that
complex for one thing... :-)

The two reasons C is better for some of this systems work IMHO are
pointer magic and the += -= *= /= &= |= ~= operators.  Nothing I
hate worse than having to write

    mystruct(ix*5-1).tag(iy+delta) = mystruct(ix*5-1).tag(iy+delta) + 1;

However after working with PL/M for 7 years I know it backwards and
forwards and therefore I *trust* it when the coding is tight and the
consequences life-or-death.  No frills but no surprises either.
-- 
Tom Neff				UUCP:     ...!uunet!bfmny0!tneff
    "Truisms aren't everything."	Internet: tneff@bfmny0.UU.NET