Re: newbie: examples of regular expressions in oracle?

bbcrock_at_hotmail.com wrote:
: I found a decent enough hack on Ask Tom at oracle.

: but I don't understand when you say that you cannot reliably edit html
: using REs. I've done it for 8 years in ColdFusion and CF had a lousy
: implementation of REs for years. I'm managing a few legacy apps
: written in PERL that make massive use of REs to share data from
: webpages (think of it as proto-RSS) that have been running for 10
: years- and they're constantly working with pages that change text,
: values, tags, etc. I've never run into errors in identifying HTML tags
: in REs and can't imagine how there would be a problem since they're so
: easily identifiably and HTML ALWAYS follows the same patterns- it's the
: quintessential RE example.

HTML is not a "regular" language ("regular" being the technical term invented by various computer scientist types for a particular class of language.) Therefore a straight forward application of regular expressions cannot parse html in every situation.

And some practical cases to consider (cut/pasted from perldoc -q html.+string).

<quote>

	Here are some tricky cases that you should think about when
	picking a solution:

	    <IMG SRC = "foo.gif" ALT = "A > B">

	    <IMG SRC = "foo.gif"
	         ALT = "A > B">

	    <!-- <A comment> -->

	    <script>if (a<b && a>c)</script>

	    <# Just data #>

	    <![INCLUDE CDATA [ >>>>>>>>>>>> ]]>

	If HTML comments include other tags, those solutions would also
	break on text like this:

	    <!-- This section commented out.
	        <B>You can't see me!</B>
	    -->

</quote>

So, if you have access to a simple to use html parser (i.e. HTML::Parser) then it is commonly worthwhile to simply use that parser instead of spending time playing with regular expressions.

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