NAME

Catmandu::Iterable - Base class for all iterable Catmandu classes

SYNOPSIS

    # Create an example Iterable using the Catmandu::Importer::Mock class
    my $it = Catmandu::Importer::Mock->new(size => 10); 

    my $array_ref = $it->to_array;
    my $num       = $it->count;

    # Loop functions
    $it->each(sub { print shift->{n} });

    my $item = $it->first;

    $it->rest
       ->each(sub { print shift->{n} });

    $it->slice(3,2)
       ->each(sub { print shift->{n} });

    $it->take(5)
       ->each(sub { print shift->{n} });

    $it->group(5)
       ->each(sub { printf "group of %d items\n" , shift->count});

    $it->tap(\&logme)->tap(\&printme)->tap(\&mailme)
       ->each(sub { print shift->{n} });

    # Select and loop
    my $item = $it->detect(sub { shift->{n} > 5 });

    $it->select(sub { shift->{n} > 5})
       ->each(sub { print shift->{n} });

    $it->reject(sub { shift->{n} > 5})
       ->each(sub { print shift->{n} });

    # Boolean
    if ($it->any(sub { shift->{n} > 5}) {
         .. at least one n > 5 ..
    }

    if ($it->many(sub { shift->{n} > 5}) {
         .. at least two n > 5 ..
    }

    if ($it->all(sub { shift->{n} > 5}) {
         .. all n > 5 ..
    }

    # Modify and summary
    my $it2 = $it->map(sub { shift->{n} * 2 });

    my $sum = $it2->reduce(0,sub { 
                my ($prev,$this) = @_;
                $prev + $this;
                });
        
    my $it3 = $it->group(2)->invoke('to_array');

DESCRIPTION

The Catmandu::Iterable class provides many list methods to Iterators such as Importers and Exporters. Most of the methods are lazy if the underlying datastream supports it. Beware of idempotence: many iterators contain state information and calls will give different results on a second invocation.

METHODS

to_array

Return all the items in the Iterator as an ARRAY ref.

count

Return the count of all the items in the Iterator.

LOOPING

each(\&callback)

For each item in the Iterator execute the callback function with the item as first argument. Returns the number of items in the Iterator.

first

Return the first item from the Iterator.

rest

Returns an Iterator containing everything except the first item.

slice(INDEX,LENGTH)

Returns an Iterator starting at the item at INDEX returning at most LENGTH results.

take(NUM)

Returns an Iterator with the first NUM results.

group(NUM)

Splitting the Iterator into NUM parts and returning an Iterator for each part.

interleave(@iterators)

Returns an Iterator which returns the first item of each iterator then the second of each and so on.

contains($data)

Alias for includes.

includes($data)

return true if any item in the collection is deeply equal to $data.

tap(\&callback)

Returns a copy of the Iterator and executing callback on each item. This method works like the Unix tee command. Use this command to peek into an iterable while it is processing results. E.g. you are writing code to process an iterable and wrote something like:

   $it->each(sub { 
          # Very complicated routine
          ....
   });

Now you would like to benchmark this piece of code (how fast are we processing). This can be done by tapping into the iterator and calling a 'benchmark' subroutine in your program that for instance counts the number of items divided by the execution time.

   $it->tap(\&benchmark)->each(sub { 
          # Very complicated routine
          ....
   });

   sub benchmark {
       my $item = shift;
       $start ||= time;
       $count++;

       printf "%d recs/sec\n" , $count/(time - $start + 1) if $count % 100 == 0;
   }

detect(\&callback)

Returns the first item for which callback returns a true value.

detect(qr/..../)

If the iterator contains STRING values, then return the first item which matches the regex.

detect($key => $val)

If the iterator contains HASH values, then return the first item where the value of $key is equal to val.

detect($key => qr/..../)

If the iterator contains HASH values, then return the first item where the value of $key matches the regex.

detect($key => [$val, ...])

If the iterator contains HASH values, then return the first item where the value of $key is equal to any of the vals given.

select(\&callback)

Returns an Iterator for each item for which callback returns a true value.

select(qr/..../)

If the iterator contains STRING values, then return each item which matches the regex.

select($key => $val)

If the iterator contains HASH values, then return each item where the value of $key is equal to val.

select($key => qr/..../)

If the iterator contains HASH values, then return each item where the value of $key matches the regex.

select($key => [$val, ...])

If the iterator contains HASH values, then return each item where the value of $key is equal to any of the vals given.

reject(\&callback)

Returns an Iterator for each item for which callback returns a false value.

reject(qr/..../)

If the iterator contains STRING values, then reject every item except those matching the regex.

reject($key => qr/..../)

If the iterator contains HASH values, then reject every item for where the value of $key DOESN'T match the regex.

reject($key => $val)

If the iterator contains HASH values, then return each item where the value of $key is NOT equal to val.

reject($key => [$val, ...])

If the iterator contains HASH values, then return each item where the value of $key is NOT equal to any of the vals given.

BOOLEAN FUNCTIONS

any(\&callback)

Returns true if at least one item generates a true value when executing callback.

many(\&callback)

Alias for many.

many(\&callback)

Returns true if at least two items generate a true value when executing callback.

all(\&callback)

Returns true if all the items generate a true value when executing callback.

MAP & REDUCE

map(\&callback)

Returns a new Iterator containing for each item the result of the callback.

reduce([START],\&callback)

Alias for reduce.

reduce([START],\&callback)

For each item in the Iterator execute &callback($prev,$item) where $prev is the option START value or the result of the previous call to callback. Returns the final result of the callback function.

invoke(NAME)

This is a shortcut for $it->map(sub { $_[0]->NAME }).

max()

min()

SEE ALSO

Catmandu::Iterator.

cpanm Catmandu

perl -MCPAN -e shell
install Catmandu