The way I would assert in a 5.8 regex that some expression, say whatever(), must be true would be.
/(?(?{! whatever() })(?!))/
Or
/(?(?{ whatever() })|(?!))/
The latter can, in 5.10, be written...
/(?(?{ whatever() })|(*FAIL))/
... which almost reads naturally as whatever or fail but this still seems unduly complex for what I would have thought would be a common desire. Indeed I've always felt that this should be the semantics of simple code constructs. (After all the documentation does call them assertions).
/(?{ whatever() })/
The above, of course, does not work because code assertions are defined to always succeed.
Is there a neater way to do this in 5.10 (or indeed 5.8) than the ways I'd currently use in 5.8?
In previous discussion Ilya Zakharevich suggested that we could add flags between the closing brackets so perhaps we could use:
/(?{ whatever() }?)/
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Replies are listed 'Best First'. | |
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Re: Regex code assertion should be able to fail
by nobull (Friar) on Sep 04, 2007 at 08:43 UTC | |
Re: Regex code assertion should be able to fail
by zshzn (Hermit) on Sep 02, 2007 at 07:23 UTC | |
by nobull (Friar) on Sep 04, 2007 at 08:39 UTC | |
by moritz (Cardinal) on Sep 04, 2007 at 08:59 UTC | |
Re: Regex code assertion should be able to fail
by diotalevi (Canon) on Sep 04, 2007 at 15:40 UTC | |
Re: Regex code assertion should be able to fail
by mmmmtmmmm (Monk) on Sep 03, 2007 at 21:46 UTC | |
by nobull (Friar) on Sep 04, 2007 at 08:34 UTC | |
Re: Regex code assertion should be able to fail
by halley (Prior) on Sep 04, 2007 at 15:21 UTC | |
by nobull (Friar) on Sep 06, 2007 at 17:22 UTC |