Ascending and Descending (SortOrder functions)

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Create SortOrder object to sort in ascending or descending order (SortOrder class)

These shared methods create a new instance of the SortOrder class. The ordering direction of the new instance is given by the method name: Ascending is low-to-high; Descending is high-to-low.

The sorting key of the new instance is specified by the input parameter to the method. This parameter is a function that gets applied to each item in the collection that is being sorted, and it must be a method that operates on the item type and returns a User Language intrinsic datatype (Float, String, Longstring, or Unicode) value.

Ascending/Descending syntax

%sortOrder = [%(SortOrder For itemType):]Ascending[( [itemFunction])]

%sortOrder = [%(SortOrder For itemType):]Descending[( [itemFunction])]

Syntax terms

%sortOrder A SortOrder object variable to contain the new object instance.
[%(SortOrder For itemType)] This optional specification of the class in parentheses denotes a virtual constructor. See "Usage notes", below, for more information about invoking a SortOrder virtual constructor.
itemFunction A method value (a method name literal, a method variable, a class Variable, or even a method that returns a method value) for a method that operates on objects of the type specified on the declaration of the collection being sorted, and that returns a numeric or string value.

The default itemFunction value as of Sirius Mods version 7.6 is the special value This, described further in the "Usage Notes," below.

Usage Notes

  • As described in "Virtual Constructor methods", Ascending and Descending can be invoked with no method object, with an explicit class specification, or with an object variable of the class, even if that object is Null:

    %sord = Descending(itemFunction) %sord = %(SortOrder for itemType):Descending(itemFunction) %sord = %sord:Descending(itemFunction)

    Note: As shown in the second of these above, if you explicitly specify the class name, you must include the item datatype of the collection to be sorted, just as on a SortOrder object variable's declaration.

  • For more information about the itemFunction parameter, see "Specifying a SortOrder's sort key method". The parameter is a method value, not a User Language expression, and you may not specify a function that itself has an argument. In order to do this, see the example using a Local function, which shows a way to apply such a function in a sort.
  • As of Sirius Mods version 7.6, the default SortOrder itemFunction value is This, a method value that is valid for User Language intrinsic method objects only. The identity method This returns the value of the method object to which it is applied. The following statements are therefore equivalent:

    %sortOrder = Descending(this) %sortOrder = Descending

    Note: Using the default SortOrder above on a non-intrinsic method object produces a compilation error.

See also