Standard Library

[JB]

Thanks for the info about regex.  I bookmarked
the website and will be using your advice.  I am
pretty new to regex and even though I’ve spent
a lot of time researching it you have helped me
tremendously.

John Balgenorth


On Aug 9, 2014, at 8:15 PM, Kay C Lan <lan.kc.macmail at gmail.com> wrote:

> On Sun, Aug 10, 2014 at 9:08 AM, JB <sundown at pacifier.com> wrote:
>> One of the things I am interested in seeing more handlers
>> and examples is regex.  It seems to be a very powerful
>> tool with very few LiveCode examples.
> 
> The matchChunk and matchText functions are pretty straight forward to
> use, it's building the regex that can be difficult if you don't live
> with it regularly. If what you really need is examples of regex then I
> highly recommend this online regex builder:
> 
> http://regex101.com/#pcre
> 
> The thing I like about it is that you can choose the 'Flavor' of regex
> it uses, so unlike other online regex builders that use Javascript,
> you can choose the same library that Livecode uses: PCRE. So if it
> works on this site it should work in LC.
> 
> Even better, if you click on the Community tab at the top of the page
> it will present you with a list of 100s and 100s of community provided
> examples of regex, explains what they do, and it's as simple as copy
> and paste into your matchChunk or matchText function to test in LC.
> 
> I will warn you though of one gotcha that is easy to trip on if you're
> an occasional user of regex + LC. The standard matchText function
> looks like this:
> 
> matchTex(yourDataVar,"regex(capturethis)expression",yourCapturedVar)
> 
> so any matches within () will be placed in your variable place holder.
> 
> In regex the | character is used as OR
> 
> so you might be looking for lowercase jpg file names, but you want
> just the name, not the extension:
> 
> ([a-z]+)\.jpg  will work, but not if you also have some with a jpeg extension.
> 
> ([a-z]+.jpeg will work for those, so these could be combined with the
> | identifier:
> 
> ([a-z]+)\.jpg|([a-z]+)\.jpeg
> 
> Now I appreciate the regex experts will point out there is a much
> better way to solve this problem than using |, but the point of this
> is, if you use | in your regex, and place it in matchText or
> matchChunk, you no longer have a single placeholder, so your matchText
> function has to be amended accordingly:
> 
> matchText(yourDataVar,"([a-z]+)\.jpg|([a-z]+)\.jpeg",myJpgFile,myJpegFile)
> 
> It is easy, when copying regex off such sites listed above, or
> building your own, and you know you are only finding x number of data
> bites, to assume that that is how many capture variables you need, but
> if OR is used, then you can easily end up needing double or triple the
> number of variables.
> 
> Rule of thumb, always count the number of capturing () in the regex
> and ensure you have the same number of allocated capturing variables.
> 
> HTH
> 
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