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Re: Mean calculation problem

by bobf (Monsignor)
on Jan 13, 2010 at 06:52 UTC ( #817118=note: print w/replies, xml ) Need Help??

in reply to Mean calculation problem

I got stuck in the regex

I would suggest starting with CPAN rather than writing your own parser. Bio::Structure::IO, Chemistry::File::PDB, Chemistry::Mol all look relevant, and there are likely several more. If you use an existing module to do the low-level work, you can focus on the real reason you are writing the code (i.e., it isn't because you want to parse a PDB file, it is because you want to do something with the contents of the file).

If you insist on rolling your own parser, look at unpack. It is great for fixed-width data, and will likely be much faster and less buggy than any regex you assemble.


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[Corion]: Aaah - you should be able to do this with overload, but I would hit somebody really hard if they constructed objects that are true but the empty string, and you not knowing about the domain knowledge where this makes sense
[Eily]: you could tie a variable into not having the same value each time, if you like to make people who try to debug your code facepalm
[Corion]: perl -wle 'package o; use overload q("") => sub {warn "str"; ""}, bool => sub{warn "bool"; 1}; package main; my $o={}; bless $o => o; print "Yay" if ($o && !length($o))'
[Corion]: But people writing such code should document the objects they construct and why it makes sense for an object to be invisible as string while being true in a boolean context
[hippo]: That's equal parts clever and horrendous.
[Eily]: the overload version wouldn't return true with "$x" && !length $x though, I guess
[hippo]: The more I look at this code, the more $x is a plain old scalar and the more this condition will never be true. I'm calling it a bug at this point.
[hippo]: Thanks for your input which has soothed my sanity (a little)
[Corion]: Eily: Sure - if you force both things into stringy things, then you break that magic. But that would also mean that you changed the expression, as now $x = 0.00 will be true instead of false as it were before

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