Re: Analyse an array and join only some elements of it

my @dna_chunks = ...;
sub your_test {
   my $string = shift;
   # do your test here, and return 1 if it passes
}

my @used = grep your_test($_), @dna_chunks;
my $long_string = join '', @used;
print "Used ", scalar(@used), " chunks, ",@dna_chunks - @used, " disca
+red";
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See grep for details.

Perl 6 - the future is here, just unevenly distributed

Comment on Re: Analyse an array and join only some elements of it Download Code

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Re^2: Analyse an array and join only some elements of it by tobyink (Canon) on Jun 15, 2012 at 13:52 UTC
The combination of `join` and `grep` sounds like it will do what you want. (`map` and `sort` and some of their friends from List::Util and List::MoreUtils are also often useful, but don't sound needed in your case.) The following example uses `join` and `grep` to filter the numbers from 1 to 20 for primes, then join the primes together into a string separated by semicolons. `sub is_prime { my $num = shift; return if $num == 1; # 1 is not prime die "usage: is_prime(NATURAL NUMBER)" unless $num =~ /^[1-9][0-9]*$/; for my $div (2 .. sqrt $num) { return if $num % $div == 0; } return 1; } my @numbers = 1 .. 20; print join ";", grep { is_prime($_) } @numbers;` [download] `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^2: Analyse an array and join only some elements of it
by tobyink (Canon) on Jun 15, 2012 at 13:52 UTC

The combination of join and grep sounds like it will do what you want. (map and sort and some of their friends from List::Util and List::MoreUtils are also often useful, but don't sound needed in your case.)

The following example uses join and grep to filter the numbers from 1 to 20 for primes, then join the primes together into a string separated by semicolons.

sub is_prime
{
   my $num = shift;
   return if $num == 1;  # 1 is not prime
   
   die "usage: is_prime(NATURAL NUMBER)"
      unless $num =~ /^[1-9][0-9]*$/;
   
   for my $div (2 .. sqrt $num)
   {
      return if $num % $div == 0;
   }
   return 1;
}

my @numbers = 1 .. 20;

print join ";", grep { is_prime($_) } @numbers;
[download]

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

[reply]
[d/l]
[select]