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Impementing UnQuickSort in Delphi How to Use the TListSortCompare function

Title: Impementing UnQuickSort in Delphi - How to Use the TListSortCompare function In the How to Randomize / Shuffle Collections and Lists article you can locate a custom Delphi function: Shuffle. Shuffle is a randomizing function that takes a TList type of object and "sorts" the items in the list in a random order - thus making the list randomized. Rawlyn, a member of the Delphi Programming Forum has a different interesting idea how to randomize the items of a Delphi list (or collection) - by sorting! Sort, but sort randomly! The TList Delphi class exposes the Sort method. Sort performs a QuickSort on the list based on the comparison function Compare. Here's the declaration of the TList.Sort method: procedure Sort(Compare: TListSortCompare) ; The TListSortCompare is actually a function type, declared as: TListSortCompare = function (Item1, Item2: Pointer): Integer; Thus, the Compare parameter of the Sort method is actually a function - Sort method takes a function as a parameter. The TListSortCompare is a function you write that indicates how the items are to be ordered. It should return a positive value if Item1 is less than (0 if they are equal, a negative value if Item1 is greater than () Item2. With the above in mind, here's an implementation of the TListSortCompare that will actually result in a randomized list. function UnSort(Item1, item2: Pointer): integer; begin result := -1 + Random(3); end; Random is a RTL function which returns a randomly generated number within a specified range. When MaxValue is specified the random number returned falls between 0 and MaxValue. Using "-1 + Random(3)" we ensure that -1, 0 or 1 are the only possible values to be returned. When -1 , 0 or 1 is "applied" as the result of the Sort method, randonmly - we have a randomizer function! Here's an example of usage: var list: TList; begin list := TList.Create; try // ** add items to the list here Randomize; list.Sort(UnSort) ; // ** list is randomized now finally FreeAndNil(List) ; end, end; Note: if you actually want to sort the items in a list holding, let's say, instances of TDeveloper by a developer name - you can use the CompareText function to compares two strings without case sensitivity.