Re: fixed point vs floating point

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Seymour says

<<Most working PL/I programmers would disagree. Strangely enough, PL/I is
like Ada (or any other programming language) in that you will get
unexpected results if you try to program before learning the language.

Periodically the PL/I people have put together task groups to redefine
the way PL/I handles precision and conversion. Invariably they have come
to the conclussion that the current way is better than any of the
proposed alternative.
>>

The fact that such task groups are periodically put together is as clear
an indication as one could get that there are problems. That they do not
succeed in improving things, especially given the burden that compatibility
imposes in this case, is hardly surprising.

What is quite significant here is that despite a significant desire in the
COBOL community to solve the same problem (and better define the semantics
of COMPUTE, now left implementation dependent), the COBOL community has
NOT decided to follow the PL/1 direction here, and I think that is definitely
wise, since I find the COBOL semantics preferable to those in PL/1.

Basically, when you avoid COMPUTE, as most COBOL programmers do, then you
must give intermediate scales and precisions explicitly, which, as I have
noted before, clearly seems the right approach to me. Ada reached a nice
comopomise, where the presence of type abstractions allows the basic
expression notation to be used, while retaining the requirement for
providing intermediate precisions and scales where they cannot be
reliably deduced by the compiler (rather than adopting the PL/1 approach
of resolving such situations with arbitrary rules that can have surprising
consequences).