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From: Johan Råde (rade_at_[hidden])
Date: 2006-08-02 04:43:34

> Johan Råde wrote:
> | I note that:
> |
> | The output from the extended_num_put facet is consistent
> | with the C99
> | standard, except that I do not put signs on NaNs. I will not change
> | that, since there is no reasonable way for a C++ program to
> | detect that sign.

Paul A. Bristow wrote:

> Surely C99 signbit tests the sign bit? (And is best used for testing the
> sign of infinity?)
> | (And the sign has no meaning anyway, unlike infinity
> | where a sign sometimes, but not always, does have meaning.)
> Mathematically, you are absolutely correct, but I have argued,
> and continue to argue strongly, that there really IS a sign bit,
> and that it is unnecessary, indeed wasteful,
> to prevent users from making some entirely private use
> of this potentially precious sign bit,
> when it costs almost nothing to simply output a '-' if the NaN has the sign
> bit set.

You are right, but our goals are different. You are working on a
proposal to the C++ standardization committee. I writing code that
should work with existing C++ compilers and std lib implementations. So
I can not assume that the C99 signbit macro is present.

What do you thing of Robert Ramey's idea of making it possible to
configure a stream to report an error when a non-finite number is
inserted or extracted? This could be done with a new stream flag and
corresponding manipulators.

--Johan Råde

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