(j3.2006) (SC22WG5.4214) [ukfortran] RE: 43 Fortran compilers

[Keith Bierman]

http://www.quadibloc.com/comp/cp0201.htm

And yes, reading the description it's easy to see how a programmer could
either be confused, or could be right ... but only in the context of the
original machine.,,, making porting those parts of the code hard.

Of course, there are people who aren't trying to write portable code. They
often live to regret it ;>


Keith Bierman
khbkhb at gmail.com
kbiermank AIM
303 997 2749


On Tue, Mar 2, 2010 at 1:25 AM, N.M. Maclaren <nmm1 at cam.ac.uk> wrote:

> On Mar 1 2010, Bill Long wrote:
>
>>
>> Indeed, M77.  I looked at the manual and found that, in 1980, M77 had the
>> radical extension of A .op. B where op was and, or, xor, ... and A and B
>> were numeric type variables, with the operations bitwise.  Only 30 years
>> ago.  Maybe this idea needs a bit more time to mature. :)
>>
>
> Or rot down?
>
> It was a major nightmare - and I don't mean just for portability.
> Even with a single compiler for a single architecture, bit-flipping
> on REAL and the sign bit of integers is beyond the ability of almost
> all programmers.  If I recall, those machines weren't twos complement,
> either, but I didn't use them directly.
>
> Restricting it to non-negative integers has worked in many languages,
> but with the ongoing problem of priority.  A == B.OR.C has been a major
> gotcha in every language that I know of that has allowed it.  Even using
> two operators for the two priorities (and, to some extent, functionality)
> helps only a little.
>
> And, yes, I do mean that porting CDC Fortran wasn't JUST a matter of
> changing its syntax - it was amazing how often one discovered that the
> original programmer had made an error with bit twiddling due to the
> above gotchas.
>
> Regards,
> Nick Maclaren.
>
>
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