Re^2: Optimize a pluggable regex matching mechanism (/o practically deprecated)

Perl's checking a regex-cache to see if it has already compiled the pattern.

No, the cache is not nearly so general. Each op simply remembers the last pattern it compiled.

>perl -Mre=debug -e"/$_/ for qw( a a b a )" 2>&1 | find "Compiling"
Compiling REx "a"
Compiling REx "b"
Compiling REx "a"
[download]

>perl -Mre=debug -e"/a/; /a/;" 2>&1 | find "Compiling"
Compiling REx "a"
Compiling REx "a"
[download]

Nothing's stopping you from making your own such cache, though.

my $compiled_pat = $compiled_pats{$pat} ||= qr/$pat/;
[download]

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Re^3: Optimize a pluggable regex matching mechanism (/o practically deprecated) by LanX (Saint) on Nov 10, 2009 at 16:52 UTC
For completeness, the following code stresses out that the last compilation per code position is reused if possible. `perl -Mre=debug -e '@x=qw/a b a a c a/; while (($a,$b,@x)=@x) { /$a/;/ +$b/ }' 2>&1\|grep Compiling Compiling REx "a" Compiling REx "b" Compiling REx "a" Compiling REx "c"` [download] Each op remembers the last pattern it compiled. Yeah, that's kind of what I expected (was too lazy for details), but a general cache would be indeed real overkill. Both ways there is not much use left for /o, IMHO the perlre and perlretut should be updated with at least footnote... Cheers Rolf	[reply] [d/l]

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Re^3: Optimize a pluggable regex matching mechanism (/o practically deprecated)
by LanX (Saint) on Nov 10, 2009 at 16:52 UTC

perl -Mre=debug -e '@x=qw/a b a a c a/; while (($a,$b,@x)=@x) { /$a/;/
+$b/ }' 2>&1|grep Compiling
Compiling REx "a"
Compiling REx "b"
Compiling REx "a"
Compiling REx "c"
[download]

Each op remembers the last pattern it compiled.

Yeah, that's kind of what I expected (was too lazy for details), but a general cache would be indeed real overkill.

Both ways there is not much use left for /o, IMHO the perlre and perlretut should be updated with at least footnote...

Cheers Rolf

[reply]
[d/l]