Re: Fixed-point

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

Jeff Carter asks

<<Jack Crenshaw's "Programmer's Toolbox" column in *Embedded Systems
Programming* has been discussing implementing multiple precision
integers and fixed-point types in C++ for some time. I was wondering
when he'd address why you'd go to the effort, rather than use a language
with fixed-point type support. In the 1997 Apr issue, he does:

"The designers of Ada ... tried to get too fancy. Instead of restricting
the type to words commensurate with the natural word length of the
computer, they gave us a more general definition that allows for words
of any bit length and any resolution. ... [T]he end result was the same:
fixed-point operations are so slow in Ada that few people bother to use
the type, and many Ada shops prohibit their use as a matter programming
style."

Has anyone encountered this phenomenon?>>


Robet replies

I doubt anyone has "encountered this phenomenon" since the quotation
is complete nonsense, and shows that the author knows nothing about
fixed-point in Ada. There are some problems with fixed-point, especially
in Ada 83, but they are essenti9ally fixed in Ada 95. For a detailed
discussion of these problems, see my repot on fixed-point, this was
one of the SEI reports done for the Ada 9X development effort.