QSORT

Portability Subroutine: Performs a quick sort on an array of rank one.

Module: USE DFPORT

Syntax

CALL QSORT (array, len, isize, compar)

array
(Input) Any type. One-dimensional array to be sorted.
If the data type does not conform to one of the predefined interfaces for QSORT, you may have to create a new interface (see below).

len
(Input) INTEGER(4). Number of elements in array.

isize
(Input) INTEGER(4). Size, in bytes, of a single element of array:

• 4 if array is of type REAL(4)
• 8 if array is REAL(8) or complex
• 16 if array is COMPLEX(8)

compar
(Input) INTEGER(2). Name of a user-defined ordering function that determines sort order. The type declaration of compar takes the form:

INTEGER(2) FUNCTION compar(arg1, arg2)

where arg1 and arg2 have the same type as array. Once you have created an ordering scheme, implement your sorting function so that it returns the following:

• Negative if arg1 should precede arg2
• Zero if arg1 is equivalent to arg2
• Positive if arg1 should follow arg2

Dummy argument compar must be declared as external.

If you use QSORT with different data types, your program must have a USE DFPORT statement in order for all the calls to work correctly. In addition, if you wish to use QSORT with a derived type or a type that is not in the predefined interfaces, you must include an overload for the generic subroutine QSORT. Examples of how to do this are in the portability module's source file, DFPORT.F90, located in your \DF98\INCLUDE subdirectory.

Compatibility

CONSOLE STANDARD GRAPHICS QUICKWIN GRAPHICS WINDOWS DLL LIB

Example

 PROGRAM SORTQ
    USE DFPORT
    integer(2), external :: cmp_function
    integer(2) insort(26), i
    integer (4) array_len, array_size
    array_len = 26
    array_size = 2
    do i=90,65,-1
      insort(i-64)=91 - i
    end do
    print *, "Before: "
    print *,insort
    CALL qsort(insort,array_len,array_size,cmp_function)
    print *, 'After: '
    print *, insort
 END
 !
    integer(2) function cmp_function(a1, a2)
    integer(2) a1, a2
    cmp_function=a1-a2
    end function