exactly-one function

The fn:exactly-one function returns its argument if the argument contains exactly one item.

Syntax

Read syntax diagramSkip visual syntax diagramfn:exactly-one( sequence-expression)
sequence-expression
Any sequence, including the empty sequence.

Returned value

If sequence-expression contains exactly one item, sequence-expression is returned. Otherwise, an error is returned.

Example

The following example uses the exactly-one function to determine whether the sequence in variable $seq contains exactly one item.

let $seq := 5
return fn:exactly-one($seq)

The value 5 is returned.