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Re^3: Perl Cannot Be Parsed: A Formal Proof (meh)

by adamk (Chaplain)
on Jan 22, 2008 at 00:14 UTC ( #663485=note: print w/replies, xml ) Need Help??


in reply to Re^2: Perl Cannot Be Parsed: A Formal Proof (meh)
in thread Perl Cannot Be Parsed: A Formal Proof

I suspect he also knew the business about rand(). But with his many hours of real life experience trying to statically parse Perl, he focused on the stronger proof -- the one that would give him the most information about what he was up against in creating PPI.

You pretty much nailed it exactly.

From a practical perspective there's about 5-10 things that, in various combinations, make Perl impossible to parse.

However, there's a big difference between what we believe and what we can prove.

And so from the perspective of knowing absolutely that Perl 5 can't be parsed, the Halting Problem approach was by far the most straight forward way to do it (at least to a layman like me).

This realization let me finally put the possibility of a complete parser out of my mind, and once I wasn't distracted by completeness any more, I had the chance to evaluate and actually define what "good enough" would mean for a "Perl 5 parser".

And that perspective on the problem was the one that took the code in the direction of the working solution.
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[stevieb]: it is exceptionally difficult I'm finding to debug a dist that is x-platform, where on each platform you're wrapping a different binary. Trying to co-ordinate a successful test run where tests are extensive is a nightmare, especially when the dist...
[stevieb]: ...you're testing is a test system itself. 10+ documented issues fixed, another half dozen found while fixing the original ones. I'm getting there...
[stevieb]: Then throw in changes to Windows that throws everything you trusted right out the window.
[shmem]: that's why it is called "Windows"
[stevieb]: shmem thanks for the 'insight' :P
[shmem]: good thing that Sun already took "OpenWindows", otherwise I'd not stop to shudder imagining an "OpenWindows" from MS
[shmem]: more garbage in, more garbage out that would be

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