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COMPRES$  PowerBASIC  Function

         

COMPRES$ function evaluates to its first parameter with all successive occurrences of characters specified by the second parameter being compressed to the single occurrence.  Special case is taken care of (see function description below).  If the second parameter is empty, all successive duplicate characters of the first parameter get compressed.



 COMPRES$  Source  Program                       Debugging program             Debugging logout

      ' COMPRES$(0.0)  Compress Character String             12/22/1988-05/30/1997
      ' --------------------------------------------------------------------------
      ' Copyright (C) 1988-1997 by Vladimir Veytsel                  www.davar.net

      ' Type ---------------------------------------------------------------------

      '    Function

      ' Description --------------------------------------------------------------

      '    COMPRES$ function returns its first parameter with all successive
      '    occurrences of characters specified by the second parameter being
      '    compressed to the single occurrence.

      ' Declaration --------------------------------------------------------------

      '    DECLARE FUNCTION COMPRES$(Strng$,Chars$)

      ' Parameters ---------------------------------------------------------------

      '    Strng$  - Character string to be compressed
      '    Chars$  - Characters, all successive occurrences of which
      '              should to be compressed to single occurrence

      ' Value --------------------------------------------------------------------

      '    Character string compressed as specified by Chars$ parameter

      ' Note ---------------------------------------------------------------------

      '    Empty Chars$ parameter specifies compression of ALL successive
      '    duplicate characters of the string.

      ' Examples -----------------------------------------------------------------

      '    COMPRES$(""      ,""   )=""
      '    COMPRES$("ABBCCC",""   )="ABC"
      '    COMPRES$("ABBCCC","A"  )="ABBCCC"
      '    COMPRES$("ABBCCC","B"  )="ABCCC"
      '    COMPRES$("ABBCCC","C"  )="ABBC"
      '    COMPRES$("ABBCCC","ABC")="ABC"

      ' Start Function -----------------------------------------------------------

           DEFINT A-Z  ' All defaulted variables are integer

           FUNCTION COMPRES$(Strng$,Chars$) PUBLIC

      ' Check Special Case (Compression Is Impossible) ---------------------------

           IF (LEN(Strng$)<2) THEN
              COMPRES$=Strng$
              EXIT FUNCTION
           END IF

      ' Form Compressed String (with the Exception of Last Symbol) ---------------

           Chars.Lngth=LEN(Chars$)
           FOR I=1 TO LEN(Strng$)-1
               Curr.Str.Symb$=MID$(Strng$,I  ,1)
               Next.Str.Symb$=MID$(Strng$,I+1,1)
               IF (( Curr.Str.Symb$<>Next.Str.Symb$)OR  _
                   ((Curr.Str.Symb$= Next.Str.Symb$)AND _
                    (Chars.Lngth>0)                 AND _
                    (INSTR(Chars$,Curr.Str.Symb$)=0))) THEN
                  Work.Str$=Work.Str$+Curr.Str.Symb$
               END IF
           NEXT I

      ' Return Function Value to the Point of Invocation -------------------------

           COMPRES$=Work.Str$+RIGHT$(Strng$,1)

      ' Finish Function ----------------------------------------------------------

           END FUNCTION
  
         

 COMPRES$  Debugging  Program                     Source program            Debugging logout

      ' COMPRES$(0.0)  Compress Character String             05/29/1997-05/30/1997
      ' --------------------------------------------------------------------------

        $INCLUDE "COMPRES"

        DECLARE FUNCTION COMPRES$(Strng$,Chars$)

        CLS
        PRINT "COMPRES$(0.0)  Compress Character String  ";DATE$;
        PRINT "  ";LEFT$(TIME$,5)
        PRINT STRING$(59,"-")
        PRINT

        PRINT "COMPRES$(''      ,''   )='"; _
               COMPRES$(""      ,""   ); "'"
        PRINT "COMPRES$('ABBCCC',''   )='"; _
               COMPRES$("ABBCCC",""   ); "'"
        PRINT "COMPRES$('ABBCCC','A'  )='"; _
               COMPRES$("ABBCCC","A"  ); "'"
        PRINT "COMPRES$('ABBCCC','B'  )='"; _
               COMPRES$("ABBCCC","B"  ); "'"
        PRINT "COMPRES$('ABBCCC','C'  )='"; _
               COMPRES$("ABBCCC","C"  ); "'"
        PRINT "COMPRES$('ABBCCC','ABC')='"; _
               COMPRES$("ABBCCC","ABC"); "'"

        PRINT
        PRINT "Execution completed - hit [Enter] to continue..."
  
         

 COMPRES$  Debugging  Logout         Source program       Debugging program

         

   COMPRES$(0.0)  Compress Character String  04-05-2002  18:39
   -----------------------------------------------------------

   COMPRES$(''      ,''   )=''
   COMPRES$('ABBCCC',''   )='ABC'
   COMPRES$('ABBCCC','A'  )='ABBCCC'
   COMPRES$('ABBCCC','B'  )='ABCCC'
   COMPRES$('ABBCCC','C'  )='ABBC'
   COMPRES$('ABBCCC','ABC')='ABC'

   Execution completed - hit [Enter] to continue...
        
      

         

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