VLU Compare (>, = or <)

Compare two VLU arrays for first one being greater than, equal to, or less than the second. The function returns 3 for greater than, 2 for equal to, 1 for less than and 0 for a leading zero error.

To include only the compare function in a DLL directly from this source file put the following lines in the DLL source:

%In_DLL = 1
#INCLUDE "CompareVLUs.bas" 

Source Code

The function CompareVLUs should compile in PowerBASIC For Windows (PBWin) Versions 8, 9 or 10 and PowerBASIC Console Compiler (PBCC) Versions 4, 5 or 6. The DEC$() function is new in PBWin 10 and PBCC 6, for earlier versions change to STR$() or FORMAT$(). All PBCC versions will ignore $$CRLF and wrap to next line at console width. The earlier versions of PB will not recognize the double $$ which means use 16 bit characters. Just remove one $ to make 8 bit characters.

'File name  Compare_VLUs.bas
'for stand alone testing
#if not %def(%In_DLL)
  #compile exe
  #dim all
  function pbmain () as long
    local TestArrayA(), TestArrayB() as dword
    local R1, R2A, R2B, R3A, R3B, R3C as long ' "R" for result
    'test for leading 0 - - - - - - - - - - - - - - - - - - -
    dim TestArrayA(10)
    dim TestArrayB(10)
    TestArrayA(10) = 1
    TestArrayB(9) = 999 'element 10 is zero.
    R1 = Compare_VLUs(TestArrayA(), TestArrayB())
    'test unequal MSD digit numbers - - - - - - - - - - - - - - -
    redim preserve TestArrayB(11)
    TestArrayB(11) = 1
    R2A = Compare_VLUs(TestArrayA(), TestArrayB())
    redim preserve TestArrayB(9)
    R2B = Compare_VLUs(TestArrayA(), TestArrayB())
    'test equal length arrays - - - - - - - - - - - - - - - - - - - -
    redim TestArrayA(9)
    redim TestArrayB(9)
    '- - with equal value . . . . . . . . . . . . . . .
    TestArrayA(9) = 1
    TestArrayB(9) = 1
    TestArrayA(0) = 1
    TestArrayB(0) = 1
    R3A = Compare_VLUs(TestArrayA(), TestArrayB())
    '- - with less than value . . . . . . . . . . . . .
    TestArrayA(0) = 0
    R3B = Compare_VLUs(TestArrayA(), TestArrayB())
    '- - with greater than value . . . . . . . . . . .
    swap TestArrayA(0), TestArrayB(0)
    R3C = Compare_VLUs(TestArrayA(), TestArrayB())

    ? "Lead 0 test is- " + dec$(R1) + " (should be 0)" + $$crlf + _
      "unequal digit count test is- " + dec$(R2A) + " (should be 1)" + $$crlf + _
      "unequal digit count test is- " + dec$(R2B) + " (should be 3)" + $$crlf + _
      "Equal digit count test-" + $$crlf + _
      "     with equal value is- " + dec$(R3A) + " (should be 2)" + $$crlf + _
      "     with less than value is- " + dec$(R3B) + " (should be 1)" + $$crlf + _
      "     with greater than value is- " + dec$(R3C) + " (should be 3)"
  end function
#endif
'+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
'Function to be included in DLL.
function Compare_VLUs alias "CompareVLUs" (byref VLU1() as dword, _
                                           byref VLU2() as dword) export as long
  local UB1, UB2, CurDig as long

  UB1 = ubound(VLU1())
  UB2 = ubound(VLU2())
  if VLU1(UB1) = 0 or VLU2(UB2) = 0 then
    goto IsLead0Err
  elseif UB1 > UB2 then
    goto IsGreaterThan
  elseif UB1 < UB2 then
    goto IsLessThan
  else 'the UBs are equal, so check digit by digit
    for CurDig = UB1 to 0 step -1
      if VLU1(CurDig) = VLU2(CurDig) then
        if CurDig = 0 then
          goto IsEqualTo
        else
          iterate for
        end if
      elseif VLU1(CurDig) > VLU2(CurDig) then
        goto IsGreaterThan
      else 'must be less than
        goto IsLessThan
      end if
    next
  end if
  goto IsLead0Err
  IsGreaterThan:
    function = 3
    exit function
  IsEqualTo:
    function = 2
    exit function
  IsLessThan:
    function = 1
    exit function
  IsLead0Err:
    function = 0
end function

Created on 24 December 2021; last edit 24 Dec 2021.