Returns the absolute value of $arg. If $arg is negative returns -$arg otherwise returns $arg. If type of $arg is one of the four numeric types xs:float, xs:double, xs:decimal or xs:integer the type of the result is the same as the type of $arg. If the type of $arg is a type derived from one of the numeric types, the result is an instance of the base numeric type.

For xs:float and xs:double arguments, if the argument is positive zero (+0) or negative zero (-0), then positive zero (+0) is returned. If the argument is positive or negative infinity, positive infinity is returned.

For detailed type semantics, see Section 7.2.1 The fn:abs, fn:ceiling, fn:floor, fn:round, and fn:round-half-to-even functions of [XQuery 1.0 and XPath 2.0 Formal Semantics].