MULTI SORT ARRAY

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4D v16.3

MULTI SORT ARRAY


MULTI SORT ARRAY ( array {; sort}{; array2 ; sort2 ; ... ; arrayN ; sortN} )

Parameter	Type	Description
array	Array	Array(s) to be sorted
sort	Operator	">" to sort by increasing order or "<" to sort by decreasing order If omitted no sort


MULTI SORT ARRAY ( ptrArrayName ; sortArrayName )

Parameter	Type	Description
ptrArrayName	Pointer array	Array of array pointers
sortArrayName	Longint array	Sort order array (1 = sort by increasing order, -1 = sort by decreasing order, 0 = synchronization with previous sorts)

Description

The MULTI SORT ARRAY command enables you to carry out a multi-level sort on a set of arrays.

This command accepts two different syntaxes.

First syntax: MULTI SORT ARRAY (array{; sort}{; array2; sort2; ...; arrayN; sortN})

This syntax is the simplest; it lets you directly pass the names of the synchronized arrays where you want to apply a multi-criteria sort.

You can pass an unlimited number of pairs (array;> or <) and/or only arrays. All the arrays passed as parameters are sorted in a synchronized manner.

You can pass arrays of any type except for Pointer or Picture arrays. You can sort an element of a two-dimensional array (i.e. a2DArray{$vlThisElement}), but you cannot sort the 2D array itself (i.e. a2DArray).

To use the contents of an array as sort criteria, pass the sort parameter. The value of the parameter (> or <) determines the order (ascending or descending) in which the array will be sorted. If the sort parameter is omitted, the contents of the array are not used as sort criteria.

Note: Keep in mind that at least one sort criterion must be passed in order for the command to work. If no sort criterion is set, an error is generated.

The sort levels are determined by the order in which the arrays are passed to the command: the position of an array with a sort criterion in the syntax determines its sort level.

Second syntax: MULTI SORT ARRAY (ptrArrayName; sortArrayName)

This syntax, more complex, is also invaluable for generic developments (for example, you can create a generic method for sorting arrays of all types, or yet again, create the equivalent of a generic SORT ARRAY command).

The ptrArrayName parameter contains the name of an array of array pointers; each element of this array is a pointer designating an array to be sorted. The sorts are performed in the order of the array pointers defined by ptrArrayName. Warning: all the arrays pointed to by ptrArrayName must have the same number of elements.

Note: ptrArrayName can be an array of local ($ptrArrayName), process (ptrArrayName) or inter-process (<>ptrArrayName) pointers. Conversely, the elements of this array must point to process or inter-process arrays only.

The sortArrayName parameter contains the name of an array in which each element indicates the sorting order (-1, 0 or 1) of the element of the corresponding array of pointers:
-1 = Sort by decreasing order.
0 = The array is not used as a sorting criterion but must be sorted according to the other sorts.
1 = Sort by increasing order.

Note: You cannot sort arrays of the Pointer or Picture type. You can sort an element of a two-dimensional array (i.e. a2DArray{$vlThisElement}), but you cannot sort the 2D array itself (i.e. a2DArray).

For each element of the ptrArrayName array, there must be a corresponding element of the sortArrayName array. Both arrays must therefore have exactly the same number of elements.

Example 1

The following example uses the first syntax: it creates four arrays and sorts them by city (ascending order) then by salary (descending order) with the last two arrays, names_array and telNum_array, being synchronized according to the previous sort criteria:

 ALL RECORDS([Employees])

 SELECTION TO ARRAY([Employees]City;cities;[Employees]Salary;salaries;[Employees]Name;

 names;[Employees]TelNum;telNums)

 MULTI SORT ARRAY(cities;>;salaries;<;names;telNums)

If you want for the names array to be used as the third sort criteria, just add > or < after the names_array parameter.
Note that the syntax:

MULTI SORT ARRAY(cities;>;salaries;names;telNums)

is equivalent to:

SORT ARRAY(cities;salaries;names;telNums;>)

Example 2

The following example uses the second syntax: it creates four arrays and sorts them by city (increasing order) and company (decreasing order); the last two arrays, names_Array and telNum_Array, being synchronized according to previous sort criteria:

 ALL RECORDS([Employees])

 SELECTION TO ARRAY([Employees]City;cities;[Employees]Company;companies;[Employees]Name;

 names;[Employees]TelNum;telNums)

 ARRAY POINTER(pointers_Array;4)

 ARRAY LONGINT(sorts_Array;4)

 pointers_Array{1}:=->cities

 sorts_Array{1}:=1

 pointers_Array{2}:=->companies

 sorts_Array{2}:=-1

 pointers_Array{3}:=->names

 sorts_Array{3}:=0

 pointers_Array{4}:=->telNums

 sorts_Array{4}:=0

 MULTI SORT ARRAY(pointers_Array;sorts_Array)

If you want the array of names be used as a third sort criterion, you need to assign the value 1 to the sorts_Array{3} element. Or else, if you want the arrays to be sorted only by the city criterion, assign the value 0 to the sorts_Array{2}, sorts_Array{3} and sorts_Array{4} elements. In this way, you obtain an identical result to SORT ARRAY(cities;companies;names;telNums;>).