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Subject Author Date
advice on good perl idiom Mike Hunter 06-03-2008
Posted by Mirco Wahab on June 3, 2008, 12:55 pm
Please log in for more thread options
 Mike Hunter wrote:
> Recently I was coding and wanted to see which of 4 strings had the
> largest result when passed to a function. This is what I ened up
> writing:
> my @roundArr;
> push @roundArr, [$A, check($goodPrefix.$A)];
> push @roundArr, [$C, check($goodPrefix.$C)];
> push @roundArr, [$T, check($goodPrefix.$T)];
> push @roundArr, [$G, check($goodPrefix.$G)];
>
> @roundArr = sort {$b->[1] <=> $a->[1]} @roundArr;
> print $roundArr[0]->[0]." wins!\n";
> The code works fine, but I can't help but think there's a better idiom
> for what I'm trying to do. I get a little bit of a creepy feeling by
> using an array, I feel like I should be doing something with a hash. I
> guess there's no way of getting around having to associate the given
> check() result with the particular input.

This can be expressed as a "Schwartzian Transform":

...

print +(
map $_->[0],
sort {$b->[1] <=> $a->[1]}
map [$_, check($goodPrefix.$_)],
$A,$C,$T,$G
)[0] . " wins!\n"


...


Regards

Mirco

Posted by Willem on June 4, 2008, 2:01 am
Please log in for more thread options
 Mike wrote:
) Hey folks,
)
) Recently I was coding and wanted to see which of 4 strings had the
) largest result when passed to a function. This is what I ened up
) writing:
)
) while (...)
) {
)
) my @roundArr;
) push @roundArr, [$A, check($goodPrefix.$A)];
) push @roundArr, [$C, check($goodPrefix.$C)];
) push @roundArr, [$T, check($goodPrefix.$T)];
) push @roundArr, [$G, check($goodPrefix.$G)];
)
) @roundArr = sort {$b->[1] <=> $a->[1]} @roundArr;
) print $roundArr[0]->[0]." wins!\n";
)
) }
)
) The code works fine, but I can't help but think there's a better idiom
) for what I'm trying to do. I get a little bit of a creepy feeling by
) using an array, I feel like I should be doing something with a hash. I
) guess there's no way of getting around having to associate the given
) check() result with the particular input.

You only want the best result, right ? So there's no need to be
remembering the other results, let alone sorting them:

sub largest {
my $fun = shift;
my $maxStr = shift;
my $maxRes = $fun->($maxStr);
for (@_) {
my $res = $fun->($_);
if ($res > $maxRes) {
        ($maxStr, $maxRes) = ($_, $res);
}
}
return $maxStr;
}

my $winner = largest(sub { check($goodPrefix.shift) }, $A, $C, $T, $G);
print "$winner wins!\n";

) Any thoughts on some awesome one-liner that I can't see?

If you don't count the 'largest' function, it's a one-liner. :-)


SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something..
No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT

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