XQuery

Constructing Numeric Values

How does a value become "numeric"? As with any type, a value may be assigned one of the numeric types in a number of ways, for example:

• It may be selected from an input document that has a schema declaring it to have a numeric type.

• It may be a numeric literal value that appears in the query and is not surrounded by quotes. For example, $price > 25.5 compares $price to the xs:decimal value 25.5.

• It may be the result of a function that returns a number, such as count($products), which returns an xs:integer.

• It may be the result of one of the standard constructor functions, such as:

  • xs:float("25.5E3"), which constructs an xs:float value from a string

  • xs:decimal($prod/price), which constructs an xs:decimal value from an element

• It may be the result of an explicit cast, such as $prod/price cast as xs:decimal.

• It may be cast automatically when it is passed to a function, such as the sum function.

The number Function

In addition to the standard type constructors, the number function is useful for telling the processor to treat a node or atomic value as a number, regardless of its declared type (if any). It returns that argument cast as an xs:double. If no argument is provided, the number function uses the context node.

One difference between using the number function and the xs:double constructor is that the number function returns the xs:double value NaN in the case that the value cannot be cast to a numeric value, whereas the xs:double constructor throws an error. ...