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Re^3: Perl Parsing Power

by BrowserUk (Patriarch)
on Sep 24, 2012 at 10:58 UTC ( [id://995353]=note: print w/replies, xml ) Need Help??


in reply to Re^2: Perl Parsing Power
in thread Perl Parsing Power

You can do that like this:

C:\test>perl -nE"my$t; /{/&&++$t or /}/&&--$t for split''; say $t ? $t + : 'good string'" {} good string {}} -1 {{}} good string {{}{}} good string {{}{}}} -1 {{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{}}}}}}}}}}}}}}}}}}}}}}}}}}}}} 11 {{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{}}}}}}}}}}}}}}}}}}}}}}}}}} 14 {{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{}}}}}}}}}}}}}}}}}}}}}}}}}}}}}} +}}}} 6 {{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{}}}}}}}}}}}}}}}}}}}}}}}}}}}}}} +}}}}}}}}}} good string

But I wouldn't call it RDP :)

The problem with doing RDP with regex is that you have to match the entire stream with one (possibly (hopefully :) composite) regex. Which is fine for yes/no booleans, but it makes both debugging the regex and reporting where and why parsing errors occur extremely messy if not impossible.


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Re^4: Perl Parsing Power
by protist (Monk) on Sep 24, 2012 at 11:16 UTC

    Unless I am mistaken, your oneliner will fail if given

    }}}{{{

    as input. It will report a false positive. It is also not RDP, although you know this ;).

    While I will not claim that regex RDP is pretty (complex parsing rarely is), it is possible, and Programming Perl discusses it in some minimal detail.

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