fn:zero-or-one
Returns a sequence if it contains zero or one items, otherwise errors
Description
The fn:zero-or-one function returns $arg if it contains zero or one items. Otherwise, the error FORG0003 is raised. This function is useful when static typing is in effect, to avoid apparent static type errors.
This description is © Copyright 2007, Priscilla Walmsley. It is excerpted from the book XQuery by Priscilla Walmsley, O'Reilly, 2007. For a complete explanation of this function, please refer to Appendix A of the book.
Arguments and Return Type
| Name | Type |
|---|---|
$arg |
item()* |
| return value | item()? |
Examples
| XQuery Example | Results |
|---|---|
zero-or-one( () ) |
() |
zero-or-one('a') |
a |
zero-or-one( ('a', 'b') ) |
Error FORG0003 |
See Also
| fn:one-or-more | Returns a sequence if it contains one or more items, otherwise errors |
| fn:exactly-one | Returns a sequence if it contains exactly one item, otherwise errors |
History
| Published On | Last Updated | Contributor(s) |
|---|---|---|
| 2006-06-27 | 2007-02-26 | W3C, XQuery 1.0 and XPath 2.0 Functions and Operators, http://www.w3.org/TR/xpath-functions/ |
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