Xquery functions:

Functions are a set of instructions bundled together to achieve a specific outcome. Functions are a good alternative to having repeating blocks of code in a program. Values can be passed to a function using variables – we call these parameters or arguments.

XQuery provides the capability to write custom functions. Listed below are the guidelines to create a custom function.

• We can use predefined XQuery functions in code.
• We can also declare custom functions as per our requirements.
• Method overloading can be used in Xquery.
• Method recursion can be used in Xquery also.

Below is the syntax to create custom functions in Xquery:

declare function prefix:function_name($parameter as datatype)
as returnDatatype
{
 ...function code here...
};

Recursive functions example:

1.

declare function local:check-num($num as xs:int)

{

 let $result :=   if($num gt 2)

then (

let $cal := ($num - 1)

return local:check-num($cal)

     )

else(

                 if($num eq 1)

                 then fn:concat("Now values of number is", $num)

                 else fn:concat("Now values of number is++++", $num)

               ) 

  

return $result   

};

local:check-num(10)

2.

declare function local:retrieve-file-name($path as xs:string)

{

  let $inside-directory := xdmp:filesystem-directory($path)/dir:entry

   for $each in $inside-directory

     return if($each/dir:type/text() eq "file")

     

     then fn:concat("inside file ==", $each/dir:filename/text())

        else local:retrieve-file-name($each/dir:pathname/text())

};

let $dir := xdmp:filesystem-directory("D:\XQuery\")/dir:entry

  for $each in $dir

    let $file-name := $each/dir:filename/text()

    let $folder-path := $each/dir:pathname/text()

    let $file-type := $each/dir:type/text()

    return

      if($file-type eq "file") then fn:concat("outside file ==", $file-name)

       else local:retrieve-file-name($folder-path)