in reply to Re^3: Combining regexes
in thread Combining regexes

If you're operating on a single string of a few dozen/hundred/thousand characters, the difference between s///g and tr/// will not be detectable.

Sorry, but that simply isn't true.

For a 3 character string tr/// takes 1/3rd the time of starting up the regex engine.

For a 30 character string, it is 1/8th the time.

And by the time you get to just 300 characters, the regex engine is already 20 times slower for this task. 

$n = 1e0; 
cmpthese -1,{
    a => q[ my $s='axb'; $s x= $n; $s=~tr[x][y]; ],
    b => q[ my $s='axb'; $s x= $n; $s=~s[x][y]g; ] 
};;
       Rate    b    a
b 1000796/s   -- -60%
a 2493375/s 149%   --

$n = 1e1; 
cmpthese -1,{
    a => q[ my $s='axb'; $s x= $n; $s=~tr[x][y]; ],
    b => q[ my $s='axb'; $s x= $n; $s=~s[x][y]g; ] 
};;
       Rate    b    a
b  234727/s   -- -87%
a 1838169/s 683%   --

$n = 1e2; 
cmpthese -1,{
    a => q[ my $s='axb'; $s x= $n; $s=~tr[x][y]; ],
    b => q[ my $s='axb'; $s x= $n; $s=~s[x][y]g; ] 
};;
      Rate     b     a
b  28926/s    --  -95%

a 585631/s 1925%    --
$n = 1e3; 
cmpthese -1,{
    a => q[ my $s='axb'; $s x= $n; $s=~tr[x][y];],
    b => q[ my $s='axb'; $s x= $n; $s=~s[x][y]g;] 
};;
     Rate     b     a
b  3087/s    --  -96%
a 76540/s 2379%    --

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Re^5: Combining regexes
by AnomalousMonk (Archbishop) on May 21, 2016 at 17:58 UTC
    ... will not be detectable.

    I should have said "will not be noticeable in practice." In fact, I will say it...

    Give a man a fish:  <%-{-{-{-<

[reply]
[d/l]
      I should have said "will not be noticeable in practice." In fact, I will say it...

      Agreed. But...

      Since there is no practical, clarity, nor conciseness advantage for this operation; why would you choose to use the less efficient over the more?

      Better methinks to get into the habit of thinking: 1 for 1 replacement of single chars, use tr///; than to have to always make a decision (or even investigate at what point) you should shift tack for this maneuverer.

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
      In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]

        Agreed. But... um...   Well, I can't really come up with any pertinent exception or counterargument here. I just wanted to make the point to davies that in the context of the OPed question, there wasn't much difference.

        Give a man a fish:  <%-{-{-{-<

[reply]
[d/l]

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