Re: is next implied in a set of if elsifs?

[James Edward Gray II]

On Wednesday, October 15, 2003, at 04:34  PM, Dan Anderson wrote:

How is speed affected in the following scenarios:

1) Using a number of if statements
i.e.
while ($foo) {
  do_1() if ($condition_1);
  do_2() if ($condition_2);
  # ...
}
Every condition of this must be tested ever time through, so yes, it's 
the slowest.  It also doesn't mean exactly the same as the other 
versions, though they may be interchangeable in many cases.  Consider:

my $x = 10;

# and then ...

$x++ if $x >= 2;
$X++ if $x >= 4;     # $x == 12
# or ...

if ($x >= 2) {
        $x++;
}
elsif ($x >=4) {
        $x++;
}                               # $x == 11
2) Using a series of if elsifs
i.e.
while ($foo) {
  if ($condition_1) {
    do_1();
  }
  elsif ($condition_2) {
  do_2();
  }
  # ...
}
3) using a series of if elsifs and calling next:
i.e.
while ($foo) {
  if ($condition_1) {
    do_1();
    next;
  }
  elsif ($condition_2) {
  do_2();
    next;
  }
  # ...
}
These two are functionally equivalent IF there is no code in the while 
loop after the if statements.  If there is code down there, it's 
skipped by the next calls.

For readability, I prefer 1 over 2.  But I figured 2 would be faster
then 1.  For readability I prefer 2 over 3, but I figure the lasts 
would
be implied in #2.  Is this the case?  Or should I bite the bullet and
use 3?
My opinion is that speed probably shouldn't be a factor at all.  We're 
comparing fractional seconds, right?  Both are faster that the user 
blinks, most likely.

I would stress that you should use the one that properly conveys your 
intent for the code.  That would be my top goal.  Use ifs/eslifs if you 
are testing a series of conditions where it's one OR the other.  Use 
all ifs if it could be this condition AND this condition.  Use next() 
if you are trying to bypass something.

Hope that helps.

James

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