Re: Side-effect arithmetic again [was: Ada ... in embedded systems]

[stt@henning.camb.inmet.com (Tucker Taft)]

Robert Dewar (dewar@cs.nyu.edu) wrote:

: I also think that the extnsion of these operators, dubious in the first
: place, to weird cases like mod is a disservice. I can put up with += in
: C but I find the use of things like %= and ^= to be tortured syntax,
: which I prefer NOT to import in any case.

As a small anecdote here relating to the "op=" operations of C, 
my most recent "favorite" bug in C code I was writing was in the following:

  if (a /= b) {
    ...
  }

The GCC compiler nicely warns you if you write "if (a = b) {" and
suggests an extra level of parentheses to emphasize that you really
want an assignment, not an equality, operator.  Unfortunately, it
isn't so helpful with the "op=" operators, and presumes that if
you use one of those, you know what you are doing.  Alas, after
writing a lot of Ada, I didn't in this case.  Of course what I meant
was "if (a != b) {".  Instead, I divided A by B, and tested the result
for non-zero-ness.  Groink!

At this point Dave Emery comes on and asks me why in the world
I am writing any code in C... ;-}

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Cambridge, MA  USA