In article <b_P7b.23593$AU.1096140@twister.southeast.rr.com>,
"Joe Gottman" wrote:
>    Why is there no standard function that will round a floating
> point number to a given number of decimal places.

There is - std::sprintf.

> We have floor() and ceil() to rounding to integers, but there
> does not seem to be any standard way to do decimal rounding,
> which is a very common task.

This would require the use of a decimal floating-point type.
However, the standard does not require the use of any particular
base, and most implementations use binary floating-point types
which cannot represent most decimal fractions precisely.  One
must instead convert to a decimal string representation.

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do-not-spam-benh@bwsint.com (Ben Hutchings) wrote in message news:<slrnbm3pmj.3o.do-not-spam-benh@tin.bwsint.com>...
...
> This would require the use of a decimal floating-point type.
> However, the standard does not require the use of any particular
> base, and most implementations use binary floating-point types
> which cannot represent most decimal fractions precisely.  One
> must instead convert to a decimal string representation.

An alternative approach would be to use scaled integers.

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   Why is there no standard function that will round a floating point number
to a given number of decimal places.  We have floor() and ceil() to rounding
to integers, but there does not seem to be any standard way to do decimal
rounding, which is a very common task.

Joe Gottman

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