Re: startSet() and endSet() for DateTime::SpanSet

[Andrew Pimlott]

On Thu, Mar 04, 2004 at 04:05:21AM +0000, [EMAIL PROTECTED] wrote:
> Andrew Pimlott wrote:
> >     $set->iterate( sub { myfunc($_); 1 } );
> 
> The result would be:   $set = [ 1 ]
> because that's the _only_ returned value.

Boy, that's confusing to me.  I didn't realize (because I didn't read
the documentation fully) that the return value of the callback replaces
the element on which it is called.  This is not what I would expect from
a method called "iterate"; I would expect iterate to ignore its return
value, so that the set would only be modified if $_[0] is modified.  I
find your examples confusing for this reason:

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

looks as though it modifies the elements because ->add is destructive.
In fact, it "also" modifies the elements via the return value.  I think
the following example would more clearly demonstrate the behavior of
->iterate.

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

Also, this makes it cumbersome to use ->iterate without modifying the
set, because you'd have to do

    sub callback {
        myfunc($_[0]);
        $_[0];
    }

At very least the documentation could be more explicit.  The first
sentences could be,

    This method modifies a set by applying a callback function to each
    element.  The element is replaced by the return value of the
    function unless the function return sundef, in which case the
    element is removed.

Andrew