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String validation

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    String validation

    I need to validate a string of characters entered in a 'get_text' dialog box. The purpose is to verify that each character falls in the range a..z, or A..Z, or is a space, or is a hyphen. All other characters, including punctuation and control key combinations would be consider 'invalid'.

    Have identified two possible approaches:

    a) cycle through the characters in the string one at a time, comparing their ascii characters to permitted 'ranges' of ascii values; or

    b) cycle through the characters in the string one at a time, and for each use *ANY to see if each is found within a longer string of permitted characters.

    Question1: which approach is apt to be faster?

    Question2: Is there a better way ?

    Thanks.

    -- tom

    #2
    RE: String validation

    Oh what tangled webs we weave....

    As an alternative solution, with no idea as to speed, you could count the number of hyphens and spaces

    counthy=0
    countsp=0
    for i = 1 to len(yourtextinput)
    if at("-",yourtextinput,i)
    counthy=counthy+1
    else if at(" ",yourtextinput,i)
    countsp=countsp+1
    end if
    next

    then remspecial yourtextinput, test the length as compared to the original length plus the number of hyphens plus the number of spaces.

    If you are dealing with relatively short character strings, I think your ascii test might be best. For longer strings?

    Good luck.

    Stan
    There can be only one.

    Comment


      #3
      RE: String validation

      Didn't quite get that right.

      Should be

      if at("-",yourtextinput,i) >0

      and

      else if at(" ",yourtextinput,i)> 0
      There can be only one.

      Comment


        #4
        RE: String validation

        for question 2:
        try the chrtran() function.


        dim valid as l
        dim valid_chr as c
        dim input as c

        valid_chr="abcdefghijklmnopqrstuvwxyz- "

        input=ui_get_text("Enter","Something")
        if chrtran(lower(input),valid_chr,space(28))=space(len(input)) then
        valid=.t.
        else
        valid=.f.
        end if

        Comment


          #5
          RE: String validation

          Hi Tom,

          The answer depends upon the length of the input string.
          For the test, I'll assume you'll uppercase the text string (saves extra compares)

          If the typical length is less than 28, I would search for each character in a permissible string, as in

          char $ "ABCDEFGHIJKLMNOPQRSTUVWXYZ -"

          If greater than 28 or so, then you need to check each character A thru Z and eliminate them from the string until the string is left with all remaining characters.

          It may be possible to skip the cycling of characters and do it all in 1 line by something like

          LogicalValue = CONTAINSI("A B C D E F G H I J K L M N O P Q R S T U V W X Y Z -",TRANSFORM(inputstring,"@!R"+REPLICATE(" X",len(inputstring))))
          .and..not.("," $ inputstring).and..not.(";" $ inputstring)

          You just have to keep adding .and..not.("x" $ inputstring) to include all special characters that are percieved as word separators by CONTAINSI. I have not totally tested this method, but seems to work basically.

          Regards,

          Ira J. Perlow
          Computer Systems Design & Associates
          [email protected]
          Regards,

          Ira J. Perlow
          Computer Systems Design


          CSDA A5 Products
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          Comment


            #6
            RE: String validation

            Peter,

            Unless chrtran() definition is wrong, your methos won't work, as it is checking for the same characters as the validation string (thus "abcdefghihjkklmnopqrstuvwxyz- " is the only one that will pass.

            I will have to see if the documentation matches reality. If it does what a function like chrtran() would be expected to do, then your method would work.

            Regards,

            Ira J. Perlow
            Computer Systems Design & Associates
            [email protected]
            Regards,

            Ira J. Perlow
            Computer Systems Design


            CSDA A5 Products
            New - Free CSDA DiagInfo - v1.39, 30 Apr 2013
            CSDA Barcode Functions

            CSDA Code Utility
            CSDA Screen Capture


            Comment


              #7
              RE: String validation

              Hi Peter,

              I checked this morning and apparently chrtran() does work as one would expect it to work, not as the documentation indicates. I always thought it should work that way, but boy is the documentation wrong!

              To make your code a bit faster and more generic, I would change it as follows;


              dim valid as l
              dim valid_chr as c
              dim input as c


              input=ui_get_text("Enter","Something")

              valid_chr="abcdefghijklmnopqrstuvwxyz- "
              valid=if(trim(chrtran(lower(input),valid_chr,len(valid_chr)))=="",.t.,.f.)


              Regards,

              Ira J. Perlow
              Computer Systems Design & Associates
              [email protected]
              Regards,

              Ira J. Perlow
              Computer Systems Design


              CSDA A5 Products
              New - Free CSDA DiagInfo - v1.39, 30 Apr 2013
              CSDA Barcode Functions

              CSDA Code Utility
              CSDA Screen Capture


              Comment


                #8
                RE: String validation

                Tom and Peter,

                Here's a final generic function


                function IsAlphabetic as L(Text as C)
                'Alpha 5 Version 5 with optional ValidChr and Flags strings
                'function IsAlphabetic as L(Text as C,ValidChr="",Flags="I")

                ' Created by Computer Systems Design & Associates
                ' Copyright 2001 Computer Systems Design & Associates, All Rights Reserved
                ' Create Date: July 21, 2001
                ' Last Update: July 21, 2001

                ' Purpose:This function checks if allowed alphabetic
                ' (or any valid character string in version 5)
                ' characters are in the the input text string

                ' Input Parameters:
                ' Text - Input text string to check
                ' ValidChr - Text string of allowable characters
                ' Flags - "I" if case insensitive, null or blank if not

                ' Output (Return Value):
                ' Returns true if only allowable characters are in the text string

                ' Errors:

                ' Examples:
                ' IsAlphabetic("ABC @def")
                ' IsAlphabetic("ABC @def","ABCDEFGHIJKLMNOPQRSTUVWXYZ @") ' Version 5
                ' IsAlphabetic("ABC @def","ABCDEFGHIJKLMNOPQRSTUVWXYZ @","I") ' Version 5

                ' Notes:

                ' Set initial return in case of an error
                IsAlphabetic=.F.

                ' Initialize optional parameters in case we are not using version 5 or greater
                dim ValidChr as c
                dim Flags as C

                ' Set Flags here to case insensitive for Version 4 and less
                Flags=""

                ' If ValidChr is blank, then set default allowable characters
                If ValidChr==""
                ValChr="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                Else
                ValChr=ValidChr
                End If

                ' Set translation string
                TrnChr=space(len(ValChr))

                ' If a space is not an allowable character,
                ' translate it to a tilde for the check
                If .not.(" " $ ValChr)
                TrnChr=TrnChr+"~"
                ValChr=ValChr+" "
                End If

                'trace.writeln("TrnChr="+TrnChr)
                'trace.writeln("ValChr="+ValChr)

                ' If "i" or "I" is in flags, then do a case insensitive check
                IF "I" $ UPPER(Flags)
                IsAlphabetic=if(trim(chrtran(UPPER(text),ValChr,TrnChr))=="",.T.,.F.)
                ELSE
                IsAlphabetic=if(trim(chrtran(text,ValChr,TrnChr))=="",.T.,.F.)
                END IF

                end function


                Regards,

                Ira J. Perlow
                Computer Systems Design & Associates
                [email protected]

                Regards,

                Ira J. Perlow
                Computer Systems Design


                CSDA A5 Products
                New - Free CSDA DiagInfo - v1.39, 30 Apr 2013
                CSDA Barcode Functions

                CSDA Code Utility
                CSDA Screen Capture


                Comment


                  #9
                  RE: String validation

                  Thanks to everyone for the ideas, the scripts, and especially the generic function.

                  Here's another approach, which seems to work instantaneously:

                  statusbar.clear()
                  statusbar.set_text("Validating entry, standby...")
                  isok = .t.
                  counter = len(inputstring)
                  for loopcount = 1 to counter
                  tv = asc(substr(insputstring,loopcount,1)) 'get ascii value of single char
                  select
                  case tv >= 65 .and. tv = 97 .and. tv

                  Comment

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