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Regular Expression Help

  • 01-02-2011 11:29am
    #1
    DC5_ITR
    Registered Users, Registered Users 2 Posts: 81 ✭✭


    Hi

    I have a requirement to meet the following criteria:

    * Textbox that can accept only numeric characters
    * Must be 6 digits in length
    * Cannot be a full-length repeating number (e.g. 444444 is bad, 444144 is ok)
    * Cannot increment or decrement sequentially (e.g. 012345 and 987654 are bad)


    I've spent some time trying to get my head around the regular expression 'mini language' but it's just not playing ball for me. Was wondering if any RegEx wizards here might be able to help please?



    Thanks in advance for any assistance


Comments

  • #2
    Malice
    Registered Users, Registered Users 2 Posts: 15,065 ✭✭✭✭Malice


    I would recommend doing the following:
    Go here and download Expresso. It's a free RegEx tool and I found it a great help when I was trying to get my head around the syntax. Expresso comes with an analyser which can help you pinpoint flaws in logic.

    One other thing you might do is, for example, restrict user input in the textbox to numeric characters only, that way your RegEx validation won't have to take that into account.


  • #3
    Skrynesaver
    Registered Users, Registered Users 2 Posts: 1,110 ✭✭✭Skrynesaver 


    if ((/^\d{6,}^/) && ( ! /^(.)\1+$/) && (! is_incremental() )){
//We're cool
}
    is_incremental/decremental is probably better implemented as a boolean function than as a regex. In fact it would be a hiddeous regex with much backtracing that would grind slowly, whereas as a boolean function you could step forward by one char and get the character at that index as an integer and compare it to the previous character to see if it differed by your increment which would be set to 1 or -1 by the first comparison.


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