my @grads = map "($x_values[$_],$y_values[$_])", 0 .. $#x_values;
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_________
broquaint

Is it really more efficient? I know that sometimes it is beneficiall to just play with the problem and try different versions of code - to spot the real root of the problem. But you don't address his problem directly, or do you?

Is it really more efficient?

I got the impression that 'efficient' was more to do with line consumption than CPU cycles, and even if it is do with CPU cycles, map should be just as fast as a foreach if not faster in this situation. Let's see ...

use strict;

use Benchmark 'cmpthese';

my @y_vals = my @x_vals = 1 .. 50;
cmpthese(-10, {
  map => sub {
    return map "($x_vals[$_],$y_vals[$_])", 0 .. $#x_vals
  },
  for => sub {
    my @ret;
    $ret[$_] = "($x_vals[$_],$y_vals[$_])"
      for 0 .. $#x_vals;
    return @ret;
  },
});

__output__

Benchmark: running for, map, each for at least 10 CPU seconds...
       for: 11 wallclock secs (10.19 usr +  0.00 sys = 10.19 CPU) @ 75
+36.80/s (n=76800)
       map: 11 wallclock secs (10.34 usr +  0.01 sys = 10.35 CPU) @ 77
+68.31/s (n=80402)
      Rate for map
for 7537/s  -- -3%
map 7768/s  3%  --
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Ever so slightly faster, but essentially negligble. As always, take with a grain of salt. But I'd say that's about as quick as your going to get without going down the dark path of optimization.
HTH

_________
broquaint

thankyou broquaint - this is exactly what I wanted ;-)

I'm puzzled why you want to convert to arrays of pairs of coordinates into a single array of strings?

The only use I can see for this is if you are going to display them as part of the html on the page you are generating? Any other use would require you to parse the strings to retrieve the numeric values and that is never going to be efficient which appears to be your main concern.

I'm completely lost by your description of "The problem is that I am working within a foreach loop iterating over 96 lines (and doing this for each line) and it is also within a CGI which chocked after ~ line 22".

If you are doing this prior to printing them either the browser as part of your page or to disk somewhere, then there is no point in building a seperate array of strings first. You can just build the strings when you print it.

A little more explaination of what it is that you are doing, with perhaps a little more of the code would probably get you better answers.

Just a point that I didn't see made in any of the other responses, although broquaint's code doesn't have this problem: scalar @array returns the number of things in the array; but since arrays are 0 indexed, that means that on the last iteration of the loop

for( 0..scalar(@x_values) )
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for( 0 .. $#x_values )
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If not P, what? Q maybe?
"Sidney Morgenbesser"

I think you'd really need to tell us why it "chocked".

The only things I can think of is that you're running out of time (browser times out) or memory. If it's time, then you're going to need to convert the data "offline" and store it in a usable form. If it's memory then maybe..

my @x = (3,67,4,2,8,45,23);
my @y = (4,7,4,89,6,4,3);

my $arrayref = merge(\@x,\@y);
undef @y;
my @newarray = @$arrayref;
undef @x;



sub merge{
  my ($x,$y) = @_;
  foreach (@$x){
    $_ = '('.$_.','.(shift @$y).')';
  }
  return $x;
}
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;)

cheers,

J

@gradient_array= ( \@x_values, \@y_values );
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$x=$gradient_array[0]->[$index];
$y=$gradient_array[1]->[$index];
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