«

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)

wana wrote:
> 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;

--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl

"wana" <> wrote in message
news: om...
> 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

On 29 Nov 2004 12:23:16 -0800, (wana) wrote:

>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
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{pop^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,

Gunnar Hjalmarsson <> wrote:
> wana wrote:
>> 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;


But you better put the word boundaries back in though!


--
Tad McClellan SGML consulting
Perl programming
Fort Worth, Texas

Tad McClellan wrote:
> Gunnar Hjalmarsson wrote:
>> wana wrote:
>>>
>>> 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;
>
> But you better put the word boundaries back in though!

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

--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl

Bob Walton <> wrote:
> wana wrote:
>
>> foreach (keys %h)
>> {
>> $a =~ s/\b$_\b/$h{$_}/g;
>> }
>>
>> I want to replace matches in string to hash key with hash value.

> 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...


--
Tad McClellan SGML consulting
Perl programming
Fort Worth, Texas