Re: min and max running values

From:
Pete Becker <pete@versatilecoding.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 06 Mar 2007 07:19:52 -0500
Message-ID:
<sZmdnSwqXqz1wXDYnZ2dnUVZ_rbinZ2d@giganews.com>
clarkcox3@gmail.com wrote:

On Mar 5, 5:33 pm, Pete Becker <p...@versatilecoding.com> wrote:

Clark Cox wrote:

On 2007-03-05 15:31:29 -0800, Pete Becker <p...@versatilecoding.com> said:

Gary Wessle wrote:

Hi
often I need to read numbers and only keep the highest or lowest.
so I do something like
int uLimit = 0;
int lLimit = 999999999999; //hoping the compiler will not complain
uLimit = val_read > uLimit ? val_read : uLimit;
lLimit = val_read < lLimit ? val_read : lLimit;
how do I choose the original lLimit?

Use the first value of val_read for both limits.

I would tend to disagree, as that would require a special case for the
first iteration of the loop.
i.e. I would prefer A to B:

Err, they do two different things. And, of course, they're written to
make A look better.

/*A*/
int maxValue = std::numeric_limits<int>::min();
int minValue = std::numeric_limits<int>::max();
while( ... )
{
 int input = getNextValue();
 maxValue = std::max(maxValue, input);
 minValue = std::min(minValue, input);
 ...
}
/*B*/
int input = getNextValue();
int maxValue = input;
int minValue = input;
do
{
 input = getNextValue();
 maxValue = std::max(maxValue, input);
 minValue = std::min(minValue, input);
}
while(...);

Let me present two versions that are biased the other way:

/*A*/
maxValue = std::numeric_limits<int>::min();
minValue = std::numeric_limits<int>::max();

while (...)
{
int input = getNextValue();
maxValue = std::max(maxValue, input);
minValue = std::min(minValue, input);
...

}

/*B*/
maxValue = minValue = getNextValue();

while (...)
{
int input = getNextValue();
maxValue = std::max(maxValue, input);
minValue = std::min(minValue, input);
...

}

Obviously B is vastly superior to the wordy, verbose, lengthy,
overwrought, wordy, redundant, and repetitive A. <g>


Even with this rewrite, I would still prefer A. I'd prefer not to do
the same thing in the loop setup as I do each iteration of the loop
(which was my main point; poorly stated as it was :) ). If all the
real code does is find the minimum and maximum then the difference is
trivial, but if something else needs to be done with the input then it
will have to be repeated; once in the loop's setup, and once in the
body of the loop.


But all that was asked for was to find the minimum or the maximum, so
the possibility that one approach may be better than another in some
other situation isn't particularly pertinent. I'm really not interested
in generating a tutorial on when to do what, just in suggesting possible
approaches.

--

    -- Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com)
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (www.petebecker.com/tr1book)

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