|Don't ask to ask, just ask|
Re^3: Looking for a flexible regex...by BrowserUk (Pope)
|on Sep 22, 2013 at 07:10 UTC||Need Help??|
See, I said there'd be more to it :)
How would I modify your regex? ... I do have areas of the script that will error if the ranges are in the wrong order
Given that you now are seeking not to just validate a string, but will need to break that string up into its components, I wouldn't use a regex. I'd probably do this:
Note: That by converting single positions to a range of 1, it avoids the need for special casing later in the code.
Now, whether that alone is sufficient validation will depend upon where the string is coming from and what you are doing with the ranges later in the script.
For example, in genomic work, these types of range lists are often (usually) the output from some previous process (Blast or similar), and are thus pretty much guaranteed to correct; ie. properly ordered, sorted, non-overlapping etc.
But, if this was manual input from a user, you might need to be more stringent. Then you have to decide what to do if the user enters:
Some of those you could correct automatically -- eg. sort the list -- others you'd have to report the errors and either die or prompt for corrections.
Of course, some people would apply the stringent tests even for input coming from a program that is "pretty much guaranteed not to make those mistakes"; and that's a value judgement you'll have to make yourself.
Also, I'm curious what is going on in your regex -- I've heard about clustering, but never really made use of it before.
It groups sub-elements of the regex so that one can apply quantifiers that affect that sub-group collectively, rather than indiviual elements.
how does the regex know how to process a string of indeterminate length?
This is an expanded explanation of my orginal regex:
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.