replace words in string with hash values

[wana]

foreach (keys %h)
{
$a =~ s/\b$_\b/$h{$_}/g;
}

I want to replace matches in string to hash key with hash value. I am
replacing acronyms with phrases where acronym is hash key. Is there a
better or different way?

thanks!

wana (on pda)

 

[Gunnar Hjalmarsson]

foreach (keys %h)
{
$a =~ s/\b$_\b/$h{$_}/g;
}

I want to replace matches in string to hash key with hash value. I am
replacing acronyms with phrases where acronym is hash key. Is there a
better or different way?

You have Perl search the whole string as many times as there are keys in
the hash. With this approach, searching the string once is sufficient:

my $keys = join '|', keys %h;
$a =~ s/($keys)/$h{$1}/g;

 

[Paul Lalli]

foreach (keys %h)
{
$a =~ s/\b$_\b/$h{$_}/g;
}

I want to replace matches in string to hash key with hash value. I am
replacing acronyms with phrases where acronym is hash key. Is there a
better or different way?

Well, here's one that's different, though not necessarily better (in
fact, quite likely worse)

$a=~ s/\b(\B+)\b/$h{$1} or $1/ge;

Rather than searching the string for each hash key, this one would
search each word in the string to determine if it is in the hash (more
correctly stated: if it has a true value in the hash). If so, replace
it with the hash value, if not, leave it as is.

Benchmarking is left as an excercise to the OP. ;-)

One comment, however: Be careful about the use of \b. While \b does
mean 'word boundary', it means Perl's definition of a 'word', which is:
[0-9a-zA-Z_]+ That means that "don't" is two words: "don" and "t".
This may or may not be what you actually want.

Paul Lalli

 

[Michele Dondi]

foreach (keys %h)
{
$a =~ s/\b$_\b/$h{$_}/g;
}

I want to replace matches in string to hash key with hash value. I am
replacing acronyms with phrases where acronym is hash key. Is there a
better or different way?

Don't know if it's "better" (depends on far too many different
things!), but

s/\b\w+\b/$h{$&}||$&/ge;

should do the job. Of course if your acronyms follow some convention
(e.g. 2 to 4 uppercase letters only) it could be improved
performance-wise:

s/\b[A-Z]{2,4}\b/$h{$&}||$&/ge;


HTH,
Michele

 

[Tad McClellan]

You have Perl search the whole string as many times as there are keys in
the hash. With this approach, searching the string once is sufficient:

my $keys = join '|', keys %h;
$a =~ s/($keys)/$h{$1}/g;

But you better put the word boundaries back in though!

 

[Gunnar Hjalmarsson]

But you better put the word boundaries back in though!

Yes, they were omitted by mistake; thanks for pointing it out.

 

[Tad McClellan]

The only thing I've got to add to what's already been
said is to watch out for regexp metacharacters in your
hash keys. I have no idea what you might count as an
"acronym". If any metacharacters do appear, you can
use \b\Q$_\E\b as your regexp to quote them.

But if a metachar could be the first or last char, then
the word boundary probably won't match where you want it to...