Quicksort - VBScript

A Quicksort class for VBScript that can handle arrays of values or objects.

This QSort class can sort arrays of values (strings, numbers) or objects.

API Reference

Quicksort class

dim sort
set sort = new QSort

Create a new Quicksort object. (You may use any name for this object; it will be called sort in the rest of this documentation.)

set sort.Compare = GetRef("sort_function")

To sort an array of objects, a custom sort function must be specified. Set the Compare property to a function reference to your sort function. To retreive a function reference in VBScript, pass the string name of the function to GetRef.

sort.Order = ORDER_ASC (default)

sort.Order = ORDER_DESC

Set the sort order to ascending (lower values sort first, default) or descending (lower values sort last).

sort.Sort anArray

Sorts anArray in-place.

Sort Functions

A sort function should take two values a and b and return according to this chart:

Condition	Result
a < b or a sorts before b	CMP_LESS (-1)
a > b or a sorts after b	CMP_GREATER (1)
a = b or a and b are equivalent	CMP_EQUAL (0)

Examples

Sorting values

To sort an array of values, nothing special needs to be done.

dim a
a = Array(4,1,9,2,7)

dim sort
set sort = new QSort
sort.Sort a

dim i
for i = 0 to UBound(a)
   if (i > 0) then Response.Write ","
   Response.Write a(i)
next

Output:

1,2,4,7,9

Sorting objects

To sort an array of objects, you must provide a custom sort routine.

class Thing
	public a
end class

function make_thing(value)
	dim t : set t = new Thing
	t.a = value
	set make_thing = t
end function

function cmp_thing(a, b)
	if (a.a < b.a) then
		cmp_thing = CMP_LESS
	elseif (a.a > b.a) then
		cmp_thing = CMP_GREATER
	else
		cmp_thing = CMP_EQUAL
	end if
end function

dim a
a = Array(make_thing(4),make_thing(1),make_thing(9),make_thing(2),make_thing(7))

dim sort
set sort = new QSort
set sort.Compare = GetRef("cmp_thing")
sort.Sort a

dim i
for i = 0 to UBound(a)
   if (i > 0) then Response.Write ","
   Response.Write a(i).a
next

Output:

1,2,4,7,9

References

• This code was derived from code online here.

Product Links

• VBScript in a Nutshell, 2nd Edition

Versions

• 1.2: Fixed bug with setting sort order. Now allows user-defined value sorts.
  Thanks to Albert Lacerda and John Ruf.
• 1.1.1: Fixed bugs in the sample code, and in the "sort order" implementation.
  Thanks to Charles Don Hall.
• 1.1: Added sort order and API reference.

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Contact Information

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