Re: Ada ad in Embedded Systems Programming stinks

[eachus@spectre.mitre.org (Robert I. Eachus)]

In article <DAG.94Sep8191257@bellman.control.lth.se> dag@control.lth.se (Dag Bruck) writes:

  > What areas, he asked curiously...  I would be greatly interested in a
  > discussion of things that C does better than Ada, in particular from
  > someone whose understanding of Ada is beyond doubt.

   The canonical example is device drivers.  But any code where the
bit representation is more important than the data's value or where
you spend a lot of time "punning" between two different views of the
same data fall in the same category.  For example, a compression
algorithm that uses variable length representations of repeated
strings.  You can write these in Ada--with liberal use of
Unchecked_Conversion--but it is more readable if you use bit
operations on integers, or union types, etc.

   Another (ancient) case was where I needed to find the first bit set
in a large Boolean array.  The trick was to convince the compiler to
use the special string processing operations, then do a conversion
from the first non-null character found to a bit offset.  (Anyone else
remember translate and test instructions?  In any case, the array was
very sparse, and this way the only use of memory bandwidth was to
fetch data.)  Could have written it in assembler, but this code was
portable.  It just wouldn't run anywhere near as fast on a different
hardware architecture.

--

					Robert I. Eachus

with Standard_Disclaimer;
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function Message (Text: in Clever_Ideas) return Better_Ideas is...