FAQ 4.8 How do I perform an operation on a series of integers? 
Author Message
 FAQ 4.8 How do I perform an operation on a series of integers?

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4.8: How do I perform an operation on a series of integers?

    To call a function on each element in an array, and collect the results,
    use:


    For example:


    To call a function on each element of an array, but ignore the results:


                    some_func($iterator);
                    }

    To call a function on each integer in a (small) range, you can use:


    but you should be aware that the ".." operator creates an array of all
    integers in the range. This can take a lot of memory for large ranges.
    Instead use:


            for ($i=5; $i < 500_005; $i++) {

                    }

    This situation has been fixed in Perl5.005. Use of ".." in a "for" loop
    will iterate over the range, without creating the entire range.

            for my $i (5 .. 500_005) {

                    }

    will not create a list of 500,000 integers.

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Sat, 09 Mar 2013 05:00:03 GMT  
 FAQ 4.8 How do I perform an operation on a series of integers?


Quote:
>    but you should be aware that the ".." operator creates an array of all
>    integers in the range. This can take a lot of memory for large ranges.
>    Instead use:


>            for ($i=5; $i < 500_005; $i++) {

>                    }

>    This situation has been fixed in Perl5.005. Use of ".." in a "for" loop
>    will iterate over the range, without creating the entire range.

>            for my $i (5 .. 500_005) {

Should be:   for my $i (5 .. 500_004) {

Quote:

>                    }

>    will not create a list of 500,000 integers.

--
David Canzi             | "If you can't learn to do something well, learn
                        | to enjoy doing it poorly." -- Ashleigh Brilliant


Sat, 09 Mar 2013 05:35:34 GMT  
 FAQ 4.8 How do I perform an operation on a series of integers?

Quote:



> >            for ($i=5; $i < 500_005; $i++) {
> >            for my $i (5 .. 500_005) {

> Should be:   for my $i (5 .. 500_004) {

Fixed, although I made the fix up in the for() so the same numbers were
in each example.

Thanks,



Tue, 12 Mar 2013 02:38:10 GMT  
 FAQ 4.8 How do I perform an operation on a series of integers?


Quote:




>> >            for ($i=5; $i < 500_005; $i++) {

>> >            for my $i (5 .. 500_005) {

>> Should be:   for my $i (5 .. 500_004) {

>Fixed, although I made the fix up in the for() so the same numbers were
>in each example.

I was trying to get 3 lines to be consistent with each other:

    for ($i=5; $i <= 500_005; $i++) {
    for my $i (5 .. 500_005) {
    will not create a list of 500,000 integers.

The list 5 .. 500_005 contains 500,001 integers.

Was that over picky?  I can never tell.

--
David Canzi             | "If you can't learn to do something well, learn
                        | to enjoy doing it poorly." -- Ashleigh Brilliant



Tue, 12 Mar 2013 19:50:05 GMT  
 
 [ 4 post ] 

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