NAME

DateTime::SpanSet - set of DateTime spans

SYNOPSIS

    $spanset = DateTime::SpanSet->from_spans( spans => [ $dt_span, $dt_span ] );

    $set = $spanset->union( $set2 );         # like "OR", "insert", "both"
    $set = $spanset->complement( $set2 );    # like "delete", "remove"
    $set = $spanset->intersection( $set2 );  # like "AND", "while"
    $set = $spanset->complement;             # like "NOT", "negate", "invert"

    if ( $spanset->intersects( $set2 ) ) { ...  # like "touches", "interferes"
    if ( $spanset->contains( $set2 ) ) { ...    # like "is-fully-inside"

    # data extraction 
    $date = $spanset->min;           # first date of the set
    $date = $spanset->max;           # last date of the set

    $iter = $spanset->iterator;
    while ( $dt = $iter->next ) {
        # $dt is a DateTime::Span
        print $dt->start->ymd;   # first date of span
        print $dt->end->ymd;     # last date of span
    };

DESCRIPTION

DateTime::SpanSet is a class that represents sets of datetime spans. An example would be a recurring meeting that occurs from 13:00-15:00 every Friday.

METHODS

from_spans

Creates a new span set from one or more DateTime::Span objects.

   $spanset = DateTime::SpanSet->from_spans( spans => [ $dt_span ] );

from_set_and_duration

Creates a new span set from one or more DateTime::Set objects and a duration.

The duration can be a DateTime::Duration object, or the parameters to create a new DateTime::Duration object, such as "days", "months", etc.
```
   $spanset =
       DateTime::SpanSet->from_set_and_duration
           ( set => $dt_set, days => 1 );
```
from_sets

Creates a new span set from two DateTime::Set objects.

One set defines the starting dates, and the other defines the end dates.
```
   $spanset =
       DateTime::SpanSet->from_sets
           ( start_set => $dt_set1, end_set => $dt_set2 );
```
The spans have the starting date closed, and the end date open, like in [$dt1, $dt2).

If an end date comes without a starting date before it, then it defines a span like (-inf, $dt).

If a starting date comes without an end date after it, then it defines a span like [$dt, inf).
empty_set

Creates a new empty set.
clone

This object method returns a replica of the given object.
set_time_zone( $tz )

This method accepts either a time zone object or a string that can be passed as the "name" parameter to DateTime::TimeZone->new(). If the new time zone's offset is different from the old time zone, then the local time is adjusted accordingly.

If the old time zone was a floating time zone, then no adjustments to the local time are made, except to account for leap seconds. If the new time zone is floating, then the UTC time is adjusted in order to leave the local time untouched.

The method returns a new object.
min / max

First or last dates in the set. These methods may return undef if the set is empty. It is also possible that these methods may return a scalar containing infinity or negative infinity.
duration

The total size of the set, as a DateTime::Duration object, or as a scalar containing infinity.

Also available as size().
span

The total span of the set, as a DateTime::Span object.
previous / next
```
  my $span = $set->next( $dt );

  my $span = $set->previous( $dt );
```
These methods are used to find a set member relative to a given datetime or span.

The return value may be undef if there is no matching span in the set.
as_list

Returns a list of DateTime::Span objects.
```
  my @dt = $set->as_list( span => $span );
```
Just as with the iterator() method, the as_list() method can be limited by a span.

If a set is specified as a recurrence and has no fixed begin and end datetimes, then as_list will return undef unless you limit it with a span. Please note that this is explicitly not an empty list, since an empty list is a valid return value for empty sets!

union / intersection / complement

Set operations may be performed not only with DateTime::SpanSet objects, but also with DateTime, DateTime::Set and DateTime::Span objects. These set operations always return a DateTime::SpanSet object.

    $set = $spanset->union( $set2 );         # like "OR", "insert", "both"
    $set = $spanset->complement( $set2 );    # like "delete", "remove"
    $set = $spanset->intersection( $set2 );  # like "AND", "while"
    $set = $spanset->complement;             # like "NOT", "negate", "invert"

intersects / contains

These set functions return a boolean value.
```
    if ( $spanset->intersects( $set2 ) ) { ...  # like "touches", "interferes"
    if ( $spanset->contains( $dt ) ) { ...    # like "is-fully-inside"
```
These methods can accept a DateTime, DateTime::Set, DateTime::Span, or DateTime::SpanSet object as an argument.
iterator / next / previous

This method can be used to iterate over the spans in a set.
```
    $iter = $spanset->iterator;
    while ( $dt = $iter->next ) {
        # $dt is a DateTime::Span
        print $dt->min->ymd;   # first date of span
        print $dt->max->ymd;   # last date of span
    }
```
The boundaries of the iterator can be limited by passing it a span parameter. This should be a DateTime::Span object which delimits the iterator's boundaries. Optionally, instead of passing an object, you can pass any parameters that would work for one of the DateTime::Span class's constructors, and an object will be created for you.

Obviously, if the span you specify does is not restricted both at the start and end, then your iterator may iterate forever, depending on the nature of your set. User beware!

The next() or previous() methods will return undef when there are no more spans in the iterator.
start_set
end_set

These methods do the inverse of the from_sets method:

start_set retrieves a DateTime::Set with the start datetime of each span.

end_set retrieves a DateTime::Set with the end datetime of each span.
iterate

Experimental method - subject to change.

This function apply a callback subroutine to all elements of a set and returns the resulting set.

The parameter $_[0] to the callback subroutine is a DateTime::Span object.
```
    [TODO - fix example]

    sub callback {
        $_[0]->add( hours => 1 );
    }

    # $set2 elements are one hour after $set elements, and
    # $set is unchanged
    $set2 = $set->iterate( \&callback );
```
If the callback returns undef, the datetime is removed from the set:
```
    sub remove_sundays {
        $_[0] unless $_[0]->start->day_of_week == 7;
    }
```
The callback can be used to postpone or anticipate events which collide with datetimes in another set:
```
    [TODO - fix example]

    sub after_holiday {
        $_[0]->add( days => 1 ) while $holidays->contains( $_[0] );
    }
```
The callback return value is expected to be within the span of the previous and the next element in the original set.

For example: given the set [ 2001, 2010, 2015 ], the callback result for the value 2010 is expected to be within the span [ 2001 .. 2015 ].

The callback subroutine may not be called immediately. Don't count on subroutine side-effects. For example, a print inside the subroutine may happen later than you expect.

SUPPORT

Support is offered through the datetime@perl.org mailing list.

Please report bugs using rt.cpan.org

AUTHOR

Flavio Soibelmann Glock <fglock@pucrs.br>

The API was developed together with Dave Rolsky and the DateTime Community.

COPYRIGHT

The full text of the license can be found in the LICENSE file included with this module.

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