Use of XQuery boolean function in XML

In this article, i will go to explain about boolean function in XQuery.
  • 1990

Boolean Function

The fn:boolean function calculates the effective boolean value of sequence. It has a argument-

  • item()*

Syntax of boolean function

fn:boolean($arg as item()*) as xs:boolean

  • If $args has no value then, it returns false.

  • If $args is  a sequence whose first item is node then, it returns true.

  • If $args is a single value of type xs:boolean is  false then, it returns false otherwise it returns true.

  • If $args is a single value of type xs:string or xdt:untypedAtomic ; length value is zero then, it returns false and if value is greater then zero then, it returns true.

  • If $args is a single value of any numeric type value is zero or NaN then, it returns false otherwise returns true.

  • If $args have any other cases then, it raises a error.

Example of boolean function
let $xyz := ("x","y","z")
 

fn:boolean($xyz) raises a error
fn:boolean($xyz[1]) returns true.
fn:boolean($xyz[0]) returns false.
fn:boolean($xyz[4]) returns false. 

Further Readings

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