Re: variation on splitting a string into elements of an array

Note that if you're using a perl as recent as perl 5.8, you can simplify your initial unpack to:

@triplets = unpack ('(a3)*', $line);
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So long as you're sure that $line has a length that is a multiple of 3. If you don't necessarily have that, you'll get trailing crud in the last element of @triplets:

# throw away trailing crud
pop @triplets if $triplets[-1] !~ /.../;
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This leads to this answer for your original question (very similar to what's already been posted)

my $line      = 'atccatccctttaat';
my @triplets  = unpack( '(a3)*', $line);
my @triplets2 = unpack( 'x(a3)*', $line);
my @triplets3 = unpack( 'xx(a3)*', $line);
# throw away trailing crud
pop @triplets  if $triplets[-1]  !~ /.../;
pop @triplets2 if $triplets2[-1] !~ /.../;
pop @triplets3 if $triplets3[-1] !~ /.../;
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If you want to start reading at some arbitrary point, you can do:

my @triplets = unpack("x${skip}(a3)*", $line);
pop @triplets if $triplets[-1]  !~ /.../;
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Of course, it might just be easier to replace $line with substr($line,$skip).

--
@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/;
map{y/X_/\n /;print}map{pop@$_}@/for@/
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Re^2: variation on splitting a string into elements of an array by bageler (Hermit) on Mar 02, 2005 at 17:49 UTC
Since you had repeating code, my preference is to put it in a loop. I'd also use length instead of /.../, it's computationally less expensive which I assume is important if you're parsing lots of sequences. `my $line = 'atccatccctttaat'; my %triplets; for (0 .. 2) { @{$triplets{$_}} = unpack(('x' x $_).'(a3)*',$line); pop @{$triplets{$_}} if length($triplets{$_}->[-1]) != 3; print "Offset $_: @{$triplets{$_}}\n"; }` [download]	[reply] [d/l]
Re^3: variation on splitting a string into elements of an array by fizbin (Chaplain) on Mar 02, 2005 at 18:11 UTC
Yeah, I thought about a loop, but I was afraid it would obscure what the code is doing - I'd certainly switch to a loop if doing more than 3 or four repetitions, and if I were doing more than two statements per offset, but at less than that the loop syntax just clutters things up. (I realize that this is a matter of personal taste, and I might change my answer depending on my mood). Good point about using `length` - again, I think my way is clearer, but I'm not sure whether that's the use of `length` or the `->`. (which you could drop) By the way, I would have written the first line of your loop as: `$triplets{$_} = [unpack("x$_ (a3)*", $line)];` [download] But that's only because I don't like using `@{$unusedvarref}` to auto-vivify. `-- @/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/; map{y/X_/\n /;print}map{pop@$_}@/for@/` [download]	[reply] [d/l] [select]