Incrementing Strings

[flyingboz]

On Several Occasions I've had to parse and manipulate strings as numbers - I finally generalized one such - might help somebody out or give someone some ideas for a Decimal Arithmetic include file. I use stuff like this a lot to

(a) generate unique filenames

( locate or search for related filenames

© locate relevant strings in reports. web pages, and other text elements

expandcollapse popup

;===============================================================================
#cs
; Description:    Given a string representation of a positive integer, add one to it.
; Syntax:          _IncrementStringAsNum($string)
; Parameter(s):  $string 
; Requirement(s):   $string must be composed solely of integers [0-9]
; Return Value(s):  On Success - Returns $result such that int($string) + 1 = int($result)
;                  On Failure : -1 if any element of $string is not an integer
;                                           -2 if StringLen($result) would be >  $stringlen($string)
; Author(s):        FlyingBoz (flyingboz@yahoo.com)
; Note(s):       
              ;This function was designed to be used as a portion of a filename - a unique incrementer,
                 ;requiring some decimal arithmetic.  The code ensures that the string is composed of valid
                 ;integers, and it is assumed that the length of the string is sufficient to handle usage.
                 ;should you desire to increment without bound, remove/ adjust the lines invoiving $max
                 ;per your requirments.  This abstracts the number of digits required, to help filesorting,
                 ;ensure filenamelength compliance, etc. as written it will not return a string of greater length
                 ;than passed.
;===============================================================================
#ce


Func _IncrementStringAsNum($a)
   
   Local $a; array containing the elements comprising the digits
   Local $max; the largest integer possible for StringLen($a[0])
   Local $result; incremented string
   $a = StringSplit($a, '')
   
   For $i = 1 To $a[0]
      $a[$i] = Int($a[$i])
      If @error Then Return -1
      
   Next
   $max = ''
   For $i = 1 To $a[0]
      $max = $max & 9
   Next
   If Int($max) = $int Then Return -2
  ;increment
   $a[$a[0]] = $a[$a[0]] + 1
  ;carry the one :)
   For $i = $a[0] To 1 Step - 1
      If $a[$i] = 10 Then
         $a[$i] = 0
         $a[$i - 1] = $a[$i - 1] + 1
      EndIf
   Next
   $result = ""
  ;build the result
   For $i = $a[0] To 1 Step - 1
      $result = $a[$i] & $result
   Next
   Return $result
EndFunc  ;==>_IncrementStringAsNum

[CephasOz]

Going from your comments, I think the following code does the same job.

Func  _IncrementStringAsNum( $sNum )
    Local $iNum = Int( $sNum ) + 1
    If Not StringIsDigit( $sNum ) Then Return -1
    If StringLen( String( $iNum ) ) > StringLen( $sNum ) Then Return -2
    Return StringFormat( "%0" & StringLen( $sNum ) & "d", $iNum )
EndFunc

The code below doesn't work properly.

1) It re-declares a parameter ($a) as a local variable,

2) It doesn't pick up strings with non-digit characters (try "A4"), and

3) It uses a variable ($int) that doesn't get assigned a value.

Hope that's helpful.

On Several Occasions I've had to parse and manipulate strings as numbers - I finally generalized one such - might help somebody out or give someone some ideas for a Decimal Arithmetic include file.  I use stuff like this a lot to

(a) generate unique filenames

( locate or search for related filenames

© locate relevant strings in reports. web pages, and other text elements

expandcollapse popup

;===============================================================================
#cs
; Description:    Given a string representation of a positive integer, add one to it.
; Syntax:          _IncrementStringAsNum($string)
; Parameter(s):  $string 
; Requirement(s):   $string must be composed solely of integers [0-9]
; Return Value(s):  On Success - Returns $result such that int($string) + 1 = int($result)
;                  On Failure : -1 if any element of $string is not an integer
;                                           -2 if StringLen($result) would be >  $stringlen($string)
; Author(s):        FlyingBoz (flyingboz@yahoo.com)
; Note(s):       
             ;This function was designed to be used as a portion of a filename - a unique incrementer,
                ;requiring some decimal arithmetic.  The code ensures that the string is composed of valid
                ;integers, and it is assumed that the length of the string is sufficient to handle usage.
                ;should you desire to increment without bound, remove/ adjust the lines invoiving $max
                ;per your requirments.  This abstracts the number of digits required, to help filesorting,
                ;ensure filenamelength compliance, etc. as written it will not return a string of greater length
                ;than passed.
;===============================================================================
#ce
Func _IncrementStringAsNum($a)
   
   Local $a; array containing the elements comprising the digits
   Local $max; the largest integer possible for StringLen($a[0])
   Local $result; incremented string
   $a = StringSplit($a, '')
   
   For $i = 1 To $a[0]
      $a[$i] = Int($a[$i])
      If @error Then Return -1
      
   Next
   $max = ''
   For $i = 1 To $a[0]
      $max = $max & 9
   Next
   If Int($max) = $int Then Return -2
 ;increment
   $a[$a[0]] = $a[$a[0]] + 1
 ;carry the one :)
   For $i = $a[0] To 1 Step - 1
      If $a[$i] = 10 Then
         $a[$i] = 0
         $a[$i - 1] = $a[$i - 1] + 1
      EndIf
   Next
   $result = ""
 ;build the result
   For $i = $a[0] To 1 Step - 1
      $result = $a[$i] & $result
   Next
   Return $result
EndFunc ;==>_IncrementStringAsNum

<{POST_SNAPBACK}>

[flyingboz]

Going from your comments, I think the following code does the same job.

Func  _IncrementStringAsNum( $sNum )
    Local $iNum = Int( $sNum ) + 1
    If Not StringIsDigit( $sNum ) Then Return -1
    If StringLen( String( $iNum ) ) > StringLen( $sNum ) Then Return -2
    Return StringFormat( "%0" & StringLen( $sNum ) & "d", $iNum )
EndFunc

I hadn't noticed the StringFormat function nice - the logic errors slipped in when migrating from a previous implementation. Nice, and efficient. ty

Edited September 2, 2005 by flyingboz