XPath/XQuery round function

Rounds a value to a specified number of decimal places, rounding upwards if two such values are equally near.

General rules: see .

The function returns the nearest (that is, numerically closest) value to $arg that is a multiple of ten to the power of minus $precision. If two such values are equally near (for example, if the fractional part in $arg is exactly .5), the function returns the one that is closest to positive infinity.

For the four types xs:float, xs:double, xs:decimal and xs:integer, it is guaranteed that if the type of $arg is an instance of type T then the result will also be an instance of T. The result may also be an instance of a type derived from one of these four by restriction. For example, if $arg is an instance of xs:decimal and $precision is less than one, then the result may be an instance of xs:integer.

The single-argument version of this function produces the same result as the two-argument version with $precision=0 (that is, it rounds to a whole number).

When $arg is of type xs:float and xs:double:

1. If $arg is NaN, positive or negative zero, or positive or negative infinity, then the result is the same as the argument.

2. For other values, the argument is cast to xs:decimal using an implementation of xs:decimal that imposes no limits on the number of digits that can be represented. The function is applied to this xs:decimal value, and the resulting xs:decimal is cast back to xs:float or xs:double as appropriate to form the function result. If the resulting xs:decimal value is zero, then positive or negative zero is returned according to the sign of $arg.