Re: [boost] Rounding, Truncating Values

From: Tom Brinkman (reportbase_at_[hidden])
Date: 2008-06-02 11:04:02

>> I'm not even sure I understand the contract.  How can you
>> round to a number of decimal places when the result is not
>> necessarily representable?

Good question.  Not sure I have an answer.  I just
evolved these algorithms becouse I couldnt find them anywhere
else.

>> Rather than an implementation, could you
>> provide an example of a documentation, stating precisely what the
>> return value should be?

Sure.  I could do that.

>> Also, if the intention is float/double/long
>> double, why templates, as opposed to three overloads?  Thanks for any
>> clarification.

Well, this is boost after all.  What tradeoffs do you see?

>> Equally useful as rounding, perhaps, would be printing to a string
>> with guaranteed rounding.  You know that printing or reading a binary
>> floating point to a decimal string representation, and back, may not
>> result in the same number.  This goes with printf and scanf, as well
>> as I/O streams (perhaps this has been corrected but I haven't seen
>> anything very sophisticated in the STL implementations I lurk in).
>> There are known algorithms to do this with guaranteed rounding, e.g.:

I'm not an expert here.  If you would be willing to advise me on
these issues, I might be persuaded to put together some
test cases and example files.  I know there alot of subtle
issues involved with rounding floating point numbers.