Re: Re: {3} Using Variables in Path Names

This is actually an interesting discussion. Let's take a look at the code for this:

# Having defined $HOME, $first, $second up above somewhere...
# Using interpolation
my $dir = "$HOME/$first/$second";

# vs. Using join
my $dir = join '/', ($HOME, $first, $second);
[download]

Personally, I find the first to be more expressive. It tells me, the reader, that you're talking about a directory structure because that's how I'm used to seeing it.

join, to me, talks about creating generic strings, usually for some cryptic file using comma-delimitation or as a way of printing out an array in a readable form.

Now, this is all personal style. I guess I'm just used to seeing it that way.

As for speed ... I haven't done the Benchmarking, but I think that interpolation might actually even be faster.

As for usability, I will agree that it's easier to manipulate a list vs. manipulating a string, but that usually doesn't really matter. Most of the time, you're manipulating said string in a recursive fashion. So, you're just adding vs. adding & subtracting (which you'd have to do if you converted the recursion to a loop).

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Comment on Re: Re: {3} Using Variables in Path Names Download Code

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Portable creation of paths by IlyaM (Parson) on Nov 28, 2001 at 21:07 UTC
My 0.02. I don't like both variants. They are not portable. It is better to use File::Spec for operations on filenames: `use File::Spec; my $dir = File::Spec->catdir($HOME, $first, $second);` [download]	[reply] [d/l]
Re^5: Using Variables in Path Names by tadman (Prior) on Nov 28, 2001 at 20:48 UTC
I suppose my rationale behind using join over string interpolation was that when working with directories, it is often advantageous to use an array instead of a string. This way you can resolve path components like '..' using pop instead of a regex. The other idea was that each piece supplied to the join would represent a single path component, which could be validated using a quick map for the extra paranoid. Of course, then $HOME would have to be split into something like @HOME. Anyway, Benchmark says: `Benchmark: timing 1000000 iterations of interpolator, joiner... interpolator: 5 wallclock secs ( 5.13 usr + 0.00 sys = 5.13 CPU) @ +194931.77/s (n=1000000) joiner: 4 wallclock secs ( 4.53 usr + 0.00 sys = 4.53 CPU) @ 22 +0750.55/s (n=1000000) Rate interpolator joiner interpolator 194932/s -- -12% joiner 220751/s 13% --` [download] From: `#!/usr/bin/perl my ($the,$fastest,$donut,$youve,$ever,$seen) = qw [ the fastest donut +you've ever seen ]; sub joiner { my $x = join ('/', $the,$fastest,$donut,$youve,$ever,$seen); } sub interpolator { my $x = "$the/$fastest/$donut/$youve/$ever/$seen"; } use Benchmark qw [ cmpthese ]; cmpthese ( 1000000, { joiner => \&joiner, interpolator => \&interpolator, } );` [download]	[reply] [d/l] [select]
Re: Re: Re: {3} Using Variables in Path Names by impossiblerobot (Deacon) on Nov 28, 2001 at 21:25 UTC
As far as I can tell, using 'join' or the concatenation operator(.) are both reasonably fast; interpolation is slower than either. Of course, you would have to do a lot of joining for it to make any difference in the speed of your program. If interpolation is more readable (which I think it is), you could always do this: `my $dir = $HOME.'/'.$first.'/'.$second;` [download] for the extra speed boost. :-) (Actually, that's kind of ugly, too. I would probably just interpolate.) Impossible Robot	[reply] [d/l]


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