The following table describes the argument for this command:

Returns the value indicated by

$arg

or, if

$arg

is not specified, the context item after atomization, converted to an

xs:double

.

The difference between using the

fn:number

function and the

xs:double

constructor is that the

fn:number

function returns the value

NaN

in the case that the argument cannot be cast to a numeric value, whereas the

xs:double

constructor will raise an error.

The following table lists some sample values and return values:

SAMPLE FUNCTION	OUTPUT
fn:number('29.99')	29.99
fn:number('ABC')	NaN
fn:number(42)	42.0
fn:number( () )	NaN
fn:number(true())	1