Ton Hospel > Heap-Simple > Heap::Simple

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Module Version: 0.13   Source  

NAME ^

Heap::Simple - Fast and easy to use classic heaps

SYNOPSIS ^

    use Heap::Simple;

    # Create a heap
    my $heap = Heap::Simple->new;
    my $heap = Heap::Simple->new(%options);

    # Put data in the heap
    $heap->insert(@new_elements);
    # Put data in a "Object" or "Any" heap with a given key
    $heap->key_insert($key1, $element1, $key2, $element2, ...);

    # Extract the top value
    $element = $heap->extract_top;      # croaks on an empty heap
    $element = $heap->extract_first;    # returns undef on an empty heap

    # Get the top value but leave it in the heap
    $element = $heap->top;              # croaks on an empty heap
    $element = $heap->first;            # returns undef on an empty heap

    # Find the top key in the heap
    $top_key = $heap->top_key;          # return infinity on an empty heap
                                        # croaks if there's no infinity
    $top_key = $heap->first_key;        # returns undef   on an empty heap

    # Ordered extract of all data whose key is not above a given value
    @elements = $heap->extract_upto($max_key);

    # Ordered extract of all data
    @elements = $heap->extract_all;

    # Empty the heap
    $heap->clear;

    # Find the number of elements
    $count = $heap->count;

    # Get all keys (not sorted)
    @keys = $heap->keys;
    # Get all values (not sorted)
    @values = $heap->values;

    # Find the key corresponding to a value
    $key = $heap->key($value);

    # Get/Set user_data
    $user_data  = $heap->user_data;
    $old_data   = $heap->user_data($new_data);

    # Get/Set infinity
    $infinity     = $heap->infinity;
    $old_infinity = $heap->infinity($new_data);

    # Get the position of a key in an element
    $key_index    = $heap->key_index;
    $key_name     = $heap->key_name;
    $key_method   = $heap->key_method;
    $key_function = $heap->key_function;

    # Return the value of several things that were set in new:
    $wrapped      = $heap->wrapped;
    $max_count    = $heap->max_count;
    $can_die      = $heap->can_die;
    $dirty        = $heap->dirty;
    $order        = $heap->order;
    @elements     = $heap->elements;
    $elements     = $heap->elements;

    # Move all elements out of each heap in @heaps and into $heap
    $heap->absorb(@heaps);      # As if doing a repeated $heap->insert
    $heap->key_absorb(@heaps);  # As if doing a repeated $heap->key_insert

    # merge already sorted arrays into a new sorted array
    # This doesn't disturb the elements already in the heap
    my $merged_aref = $heap->merge_arrays($aref1, $aref2, ...);

    # Which class does the actual work ?
    $implementation = Heap::Simple->implementation;

EXAMPLE1 ^

When key and value are kept separate:

    use Heap::Simple;
    my $heap = Heap::Simple->new(elements => "Any");

    $heap->key_insert(8, "bar");
    $heap->key_insert(5, "foo");

    # This will print foo (5 is the lowest key)
    print "First value is ", $heap->extract_top, "\n";

    $heap->key_insert(7, "baz");

    # This will print baz (7 is the lowest key)
    print "Next value is ", $heap->extract_top, "\n";
    # This will print bar (8 is now the lowest key)
    print "Next value is ", $heap->extract_top, "\n";

EXAMPLE2 ^

When the key is part of the value:

    # This is purely for display, ignore it
    use Data::Dumper;
    $Data::Dumper::Indent = 0;
    $Data::Dumper::Terse = 1;

    # Real code starts here
    use Heap::Simple;
    my $heap = Heap::Simple->new(elements => "Array");

    $heap->insert([8, "bar"]);
    $heap->insert([5, "foo"]);

    # This will print [5, foo] (5 is the lowest key)
    print "First value is ", Dumper($heap->extract_top), "\n";

    $heap->insert([7, "baz"]);

    # This will print [7, baz] (7 is the lowest key)
    print "Next value is ", Dumper($heap->extract_top), "\n";
    # This will print [8, bar] (8 is now the lowest key)
    print "Next value is ", Dumper($heap->extract_top), "\n";

DESCRIPTION ^

A heap is a partially sorted structure where it's always easy to extract the smallest element. If the collection of elements is changing dynamically, a heap has less overhead than keeping the collection fully sorted.

The order in which equal elements get extracted is unspecified.

The main order relations supported by this module are "<" (numeric compare) and "lt" (string compare).

The module allows you to manage data where the elements are of several allowed types, in particular array references, hash references, objects or just the keys themselves.

So new has a lot of ways to specify element types, but the right choices follows quite directly from the data you'll put in the heap. If the key is part of the data (or easily derived from the data), choose an element type that tells how to get the key out of the data, and insert elements using insert. If the key is independent from the data or you want to avoid repeated key calculations, use the Any element type and insert elements using key_insert.

The internals of the module do nothing with the elements inserted except inspecting the key. This means that if you for example store a blessed object, that's what you will get back on extract. It's also ok to keep references to the elements around and make changes to them while they are in the heap as long as you don't change the key.

Heap::Simple itself is just a loader for the code that will actually implement the functionality mentioned above. You will need to install something like Heap::Simple::XS or Heap::Simple::Perl to be able to actually do anything.

EXPORT ^

None.

METHODS ^

All methods that can fail will thrown an exception in case of failure unless otherwise specified. For example, you don't have to explicitely check the result of new, it will already thrown an exception in case of bad arguments.

my $heap = Heap::Simple->new

This simplest form creates a new (empty) heap object able to hold numeric keys.

You could for example use this to print a list of numbers from low to high:

    use Heap::Simple;

    my $heap = Heap::Simple->new;
    $heap->insert(8, 3, 14, -1, 3);
    print $heap->extract_top, " " for 1..$heap->count;
    print "\n";
    # Will print: -1 3 3 8 14

This example is silly of course. You could just as well directly use perl sort. But in real applications you would do the inserting interleaved with extracting and always keeping the list sorted would become inefficient for big lists. That is where you would use a heap. The examples we give will however be like the one above so you can quickly see the way in which the methods are supposed to be called.

For some applications this basic usage where you just store numeric keys will be good enough, but usually you want to be able to store more complex elements.

Several options can help you with that:

order => $order

$order indicates what operation is used to compare keys. Supported orders are:

<

Indicates that keys are compared as numbers, and extraction is lowest value first. This is actually the default order, so the example above could have used:

    my $heap = Heap::Simple->new(order => "<");

and the result would have been exactly the same.

The default infinity for this order is +inf.

>

Indicates that keys are compared as numbers, and extraction is highest value first.

Repeating the example with this order gives:

    use Heap::Simple;

    my $heap = Heap::Simple->new(order => ">");
    $heap->insert(8, 3, 14, -1, 3);
    print $heap->extract_top, " " for 1..$heap->count;
    print "\n";
    # Will print: 14 8 3 3 -1

The default infinity for this order is -inf.

lt

Indicates that the keys are compared as strings, and extraction is lowest value first. So we could modify the "<" example to:

    use Heap::Simple;

    my $heap = Heap::Simple->new(order => "lt");
    $heap->insert("ate", 8, 3, "zzzz", 14, -1, 3, "at");
    print $heap->extract_top, " " for 1..$heap->count;
    print "\n";
    # Will print: -1 14 3 3 8 at ate zzzz

Notice how 14 comes before 3 as you would expect in lexical sorting.

The default infinity for this order is "undef" (there is no maximum string)

gt

Indicates that the keys are compared as strings, and extraction is highest value first. The concept of "minimum" again becomes rather confusing. The standard example now becomes:

    use Heap::Simple;

    my $heap = Heap::Simple->new(order => "gt");
    $heap->insert("ate", 8, 3, "zzzz", 14, -1, 3, "at");
    print $heap->extract_top, " " for 1..$heap->count;
    print "\n";
    # Will print: zzzz ate at 8 3 3 14 -1

The default infinity for this order is "" (the empty string)

$code_reference

If your keys are completely weird things, ordered neither as numbers nor as strings and you need a special compare function, you can use this general ordering type.

Every time two keys need to be compared, the given code reference will be called like:

    $less = $code_reference->($key1, $key2);

This should return a true value if $key1 is smaller than $key2 and a false value otherwise. $code_reference should imply a total order relation, so it needs to be transitive.

Since in this case nothing can be determined about the key type, there will be no infinity by default (even if the keys are numbers).

Example:

    use Heap::Simple;

    sub more { return $_[0] > $_[1] }

    my $heap = Heap::Simple->new(order => \&more);
    $heap->insert(8, 3, 14, -1, 3);
    print $heap->extract_top, " " for 1..$heap->count;
    print "\n";
    # Will print: 14 8 3 3 -1

The code reference will be called many times during normal heap operations (O(log n) times for a single insert or extract on a size n heap), so only use this order type within reason. Usually it's better to precalculate some number or string representation of some sort of key and use normal compares on these. You can use the Any element type and key_insert to wrap the precalculated key with the corresponding element, or you can delegate the key calculation to the insert method and use one of the Method, Object or Function element types.

Here's an example of such "fake" keys:

    # "human" sorting mixed strings
    use Heap::Simple;

    sub key {
        my $str = uc(shift);
        $str =~ s|(0*)(\d+)|pack("AN/A*N", "0", $2, length($1))|eg;
        return $str;
    }

    my $heap = Heap::Simple->new(order => "lt",
                                 elements => [Function => \&key]);
    $heap->insert(qw(Athens5.gr Athens40.gr
                     Amsterdam51.nl Amsterdam5.nl amsterdam20.nl));
    print $heap->extract_top, "\n" for 1..$heap->count;
    # This will print:
    Amsterdam5.nl
    amsterdam20.nl
    Amsterdam51.nl
    Athens5.gr
    Athens40.gr
elements => $element_type

This option describes what sort of elements we will store in the heap. The only reason the module needs to know this is to determine how to access the key values.

The $element_type is usually an array reference, but if the array has only one entry, you may use that directly. So you can use:

    elements => "Scalar"

instead of:

    elements => ["Scalar"]

The following element types are currently supported:

["Scalar"]

Indicates that the elements are the keys themselves. This is the default if no elements option is provided. So the constructor in the previous example could also have been written as:

    my $heap = Heap::Simple->new(order => "lt",
                                 elements => ["Scalar"]);

or in the simplified notation:

    my $heap = Heap::Simple->new(order => "lt", elements => "Scalar");

This element type used to be called Key, and that name is still accepted for backward compatibility.

[Array => $index]

Indicates that the elements are array references, with the key at index $index. So now the element can be not just the key, but also associated data. We can use this to for example print the values of a hash ordered by key:

    use Heap::Simple;

    my $heap = Heap::Simple->new(order => "lt",
                                 elements => [Array => 0]);
    while (my ($key, $val) = each %hash) {
        $heap->insert([$key, $val]);
    }
    for (1..$heap->count) {
        print $heap->extract_top->[1], "\n";
    }

You can always use something like [$key, @data] to pair up keys and data, so the "Array" element type is rather generally useful (but see the Object and Any element types for another way to pair keys with data). Since it's so common to have the key in the first position, you may in fact drop the index in that case, so the constructor in the previous example could also be written as:

    my $heap = Heap::Simple->new(order => "lt",
                                 elements => ["Array"]);

or using the one element rule:

    my $heap = Heap::Simple->new(order => "lt",
                                 elements => "Array");

In case the elements you want to store are arrays (or array based objects (or fields based objects) and you are prepared to break the object encapsulation), this element type is also very nice. If for example the value on which you want to order is a number at position 4, you could use:

    my $heap = Heap::Simple->new(elements => [Array => 4]);
    print "The key is $object->[4]\n";
    $heap->insert($object);
[Hash => $key_name]

Indicates that the elements are hash references, where the key (for the heap element) is the value $element->{$key_name} .

Redoing the Array example in Hash style gives:

    use Heap::Simple;

    my $heap = Heap::Simple->new(order => "lt",
                                 elements => [Hash => "tag"]);
    while (my ($key, $val) = each %hash) {
        $heap->insert({tag => $key, value => $val});
    }
    for (1..$heap->count) {
        print $heap->extract_top->{value}, "\n";
    }

In case the elements you want to store are hashes (or hash based objects and you are prepared to break the object encapsulation), this element type is also very nice. If for example the value on which you want to order is a number with key "price", you could use:

    my $heap = Heap::Simple->new(elements => [Hash => "price"]);
    print "The key is $object->{price}\n";
    $heap->insert($object);
[Method => $method_name]

In case you don't want to (or can't) break the object encapsulation, but there is a method that will return the key for a given object, you can use this.

The method method_name will be called like:

    $key = $element->$method_name();

and should return the key corresponding to $element.

Suppose that the elements are objects whose weight you can access using the "weight" method. A heap ordered on weight then becomes:

    my $heap = Heap::Simple->new(elements => [Method => "weight"]);
    print "The key is ", $object->weight(), "\n";
    $heap->insert($object);
[Object => $method_name]

The drawback of the "Method" element type is that the method will be called every time the internals need ordering information, which will be O(log n) for a single insert or extract on a heap of size n. So it's usually better to first extract the key before insert, wrap the object with the key such that key access is cheap and insert that. Since this is so common, this element type is provided for that.

So this element type will only call $method_name once on the initial insert, after which internally the key is stored together with the value. This makes it faster, but it also uses more memory.

It also means that it's now perfectly fine to make changes to the object that change the key while it is in the heap. This will have absolutely no influence on the ordering anymore, and methods like first_key will still return what the key value was at insert time.

Repeating the previous example in this style is a trivial variation:

    my $heap = Heap::Simple->new(elements => [Object => "weight"]);
    print "The key is ", $object->weight(), "\n";
    $heap->insert($object);

Since for this element type the key is almost completely decoupled from the value and only fetched on insert, it often makes sense to not let the heap calculate the key, but do it yourself before the insert, and then use key_insert. In fact, if you never use plain insert at all, you don't even have to bother passing a method name (though in that case the fact that the thing you store is an object is pretty irrelevant and it's probable more natural to use the Any element type).

[Function => $code_reference]

For completely general key calculation you can use this element type. The given code reference will be called on an element like:

    $key = $code_reference->($element);

and should return the key corresponding to $element.

An example:

    sub price {
        my $items = shift;
        my $price = 0;
        $price += $_->price for @$items;
        return $price;
    }

    my $heap = Heap::Simple->new(elements => [Function => \&price]);
    print "All items together will cost ", $item_list->price, "\n";
    $heap->insert($item_list);
[Any => $code_reference]

The same discussion as under Object applies for Function: single insert and extract on a size n heap will call the code reference O(log n) times, which could get slow.

So if you are prepared to use more memory, you can again tell Heap::Simple to calculate the key already at insert time, and store it together with the value. This will avoid the need for repeated key calculations.

The "Any" element type will do this for you transparantly.

The heap part of the above example becomes:

    my $heap = Heap::Simple->new(elements => [Any => \&price]);
    print "All items together will cost ", $item_list->price, "\n";
    $heap->insert($item_list);

Since for this element type the key is almost completely decoupled from the value and only fetched on insert, it often makes sense to not let the heap calculate the key, but do it yourself before the insert, and then use key_insert. In fact, if you never use plain insert at all, you don't even have to bother passing the code reference. So the last example could look like:

    my $heap = Heap::Simple->new(elements => "Any");
    my $price = $item_list->price;
    print "All items together will cost $price\n";
    $heap->key_insert($price, $item_list);

Or we can use it to simplify the hash sort on key example a bit:

    use Heap::Simple;

    my $heap = Heap::Simple->new(order => "lt",
                                 elements => "Any");
    # A hash in list context returns a sequence of key/value pairs
    $heap->key_insert(%hash);
    for (1..$heap->count) {
        print $heap->extract_top, "\n";
    }
max_count => $natural_number

Normally a heap can contain any number of elements. By passing a positive integer as argument to max_count, you tell the heap that it should never contain more values than that. If you try to insert something new when the maximum is reached, the lowest element (with respect to the current order) is dropped (the thing just being inserted is among the candidates for dropping).

A max count of 0 may or may not be supported depending on the implementor.

You can for example use this to efficiently determine the three highest values in an array:

    use Heap::Simple;

    my @array = qw(19 3 7 -5 3 18 1);

    my $heap = Heap::Simple->new(max_count => 3);
    $heap->insert(@array);
    print "The three highest values are: ", join(", " => $heap->values), "\n";

    # Will print: The three highest values are: 7, 19, 18
can_die => $bool

If you use magic values, overload, order functions or key access functions, then it's possible for external perl code to run when you do heap operations like insert or extract_top. If these throw an exception, the heap can be left in an incorrect half changed state.

If you give a true value to can_die, the code for single element operations will be changed so that they will properly recover by undoing what just got changed (so a failing operation becomes a no-op). This however will slow down these operations somewhat, so the default is actually false (most of the time getting exceptions during the heap operations is impossible anyways).

Operations that insert or extract multiple elements will also get their code changed so the heap is always left in a consistent state, but the operation is not atomic since it could already be executed on some of the elements. You could even lose elements if for example an extract_all fails halfway through (the already extracted part is gone from the heap but you never got a chance to store the methods return values).

Multi element operations can be substantially more efficient without this flag since it may allow the use of better algorithms.

This is a per heap option, so only those heaps that actually set this will see any slowdown.

All operations that don't change the heap (like count or top) are always safe.

Note that all change operations always assume you won't recursively cause another change to the same heap while they are running. If you do that, all bets for consistency are are off, even if you set this option.

dirty => $bool

Giving this option a true value means that the code may make optimistic assumptions to gain more speed. These can be things like for example ignoring overloads, casting all numbers to doubles, ignoring locale for string order, caching keys etc. The particular optimizations done under dirty will be safe for most applications though. See the documentation for a particular implementor (like Heap::Simple::XS or Heap::Simple::Perl) for what the dirty option does for that package.

The default is no dirty optimizations.

user_data => $user_data

You can associate one scalar worth of user data with any heap. That scalar can of course also be a reference to a more complex data structure, allowing you to effectively associate any amount of data with the heap. This option allows you to set this scalar value already at object creation. You can use the user_data method to get/set the associated value.

If this option is not given, the heap starts with "undef" associated to it.

    my $heap = Heap::Simple->new(user_data => "foo");
    print $heap->user_data, "\n";
    # prints foo
infinity => $infinity

Associates $infinity as the highest possible key with the created heap. ($infinity may or may not be a possible key itself). Setting it to "undef" means there is no infinity associated with the heap.

The default value depends on the order relation that was specified.

Usually you can just forget about this option. Only top_key really cares.

Notice that the class into which the resulting heap is blessed will not be Heap::Simple. It will be an on demand generated class that will have Heap::Simple as an ancestor.

$heap->insert(@new_elements)

Inserts each of the @new_elements in the heap. On extraction you get back exactly the same $element as you inserted, including a possible blessing.

In case an exception is raised during insert the heap is only guaranteed to be in a consistent state if you had set the can_die flag to new. Even then it's possible that some first part of @new_elements has been inserted into the heap while the rest hasn't (they get inserted in the order given). You could check how many by calling the count method before and after the insert. So even with can_die only inserts of single elements are atomic.

Mass insert can be substantially faster if the can_die flag isn't set though.

$heap->key_insert($key1, $element1, $key2, $element2, ...)

Inserts each $element in the heap ordered by the $key given just before it. Since in this case the key must be stored seperately from the element, this method only exists for "Object" and "Any" heaps.

On extraction you get back exactly the same $element as you inserted, including a possible blessing.

In case an exception is raised during insert the heap is only guaranteed to be in a consistent state if you had set the can_die flag to new. Even then it's possible that some first part of the argument list has been inserted into the heap while the rest hasn't (they get inserted in the order given). You could check how many by calling the count method before and after the insert. So even with can_die only inserts of single key/element pairs are atomic.

Mass insert can be substantially faster if the can_die flag isn't set though.

$element = $heap->extract_top

For all elements in the heap, find the top one (the one that is "lowest" in the order relation), remove it from the heap and return it.

This method used to be called "extract_min" instead of "extract_top". The old name is still supported but is deprecated.

Throws an exception if the heap is empty.

$element = $heap->extract_first

Like extract_top, but if the heap is empty it will return undef (in scalar context).

$element = $heap->top

For all elements in the heap, find the top one (the one that is "lowest" in the order relation) and return it (without removing it from the heap)..

Throws an exception if the heap is empty.

$element = $heap->first

For all elements in the heap, find the top one (the one that is "lowest" in the order relation) and return it (without removing it from the heap).For all elements in the heap, find the one with the lowest key and return it. Returns undef (in scalar context) in case the heap is empty. The contents of the heap remain unchanged.

Since the data returned from a non-empty heap can often not be undef, you could use this method to check if a heap is empty, but it's probably more natural to use count for that.

Example:

    use Heap::Simple;

    my $heap = Heap::Simple->new;
    $heap->insert(8, 3, 14, -1, 3);
    print $heap->first, "\n";
    # prints -1
$top_key = $heap->first_key

Looks for the lowest key in the heap and returns its value. Returns undef (in scalar context) in case the heap is empty

Example:

    use Heap::Simple;

    my $heap = Heap::Simple->new;
    $heap->insert(8, 3, 14, -1, 3);
    print $heap->first_key, "\n";
    # prints -1
$top_key = $heap->top_key

Looks for the lowest key in the heap and returns its value. Returns the highest possible value (the infinity for the chosen order) in case the heap is empty. If there is no infinity, it will throw an exception.

Example:

    use Heap::Simple;

    my $heap = Heap::Simple->new;
    $heap->insert(8, 3, 14, -1, 3);
    print $heap->top_key, "\n";
    # prints -1

This method used to be called "min_key" instead of "top_key". The old name is still supported but is deprecated.

@elements = $heap->extract_upto($max_key)

Finds all elements in the heap whose key is not above $value and removes them from the heap (so elements with key equal to $max_key get extracted too). The list of removed elements is returned ordered by key value (low to high with repect to the heap order).

Returns an empty list for the empty heap.

Example:

    use Heap::Simple;

    my $heap = Heap::Simple->new;
    $heap->insert(8, 3, 14, -1, 3);
    print join(", ", $heap->extract_upto(3)), "\n";
    # prints -1, 3, 3

This method will lose values in case of an exception even if can_die is true (remember that exceptions of this type are only possible if you have a self coded key fetch or compare that can die, so this is normally irrelevant).

@elements = $heap->extract_all

Extracts all elements from $heap and returns them ordered by key value (low to high with repect to the heap order).

Example:

    use Heap::Simple;

    my $heap = Heap::Simple->new;
    $heap->insert(8, 3, 14, -1, 3);
    print join(", ", $heap->extract_all), "\n";
    # prints -1, 3, 3, 8, 14

This method can lose values in case of an exception even if can_die is true (remember that exceptions of this type are only possible if you have a key fetch or compare that can die, so this is normally irrelevant).

If you don't actually care about the order of the elements it's more efficient to use values followed by clear.

It's unspecified what this method returns in scalar context.

$heap->clear

Removes all elements from the heap. This can be much more efficient than using extract_all in a void context.

$count = $heap->count

Returns the number of elements in the heap. This is an constant time operation, it doesn't really need to count anything.

    use Heap::Simple;

    my $heap = Heap::Simple->new;
    $heap->insert(8, 3, 14, -1, 3);
    print $heap->count, "\n";
    # prints 5
@keys = $heap->keys

Returns the keys of all elements in the heap in some heap order. This means that the element at index n is not bigger (in the heap order) than the element at index 2*n+1 and 2*n+2. So the top key will in fact be in the first position, but don't expect the whole list to be ordered.

This method may imply a lot of function calls if getting the key from an element implies a function call (as it does for the Method and Function element types, but not for the Object and Any element types).

Multiple calls to an unchanged heap will return the keys in the same order, which is also consistent with the order of values

@values = $heap->values

Returns all elements in the heap in some heap order with respect to the corresponding keys (see keys). Does not remove the values from the heap.

Multiple calls to an unchanged heap will return the values in the same order, which is also consistent with the order of keys

$key = $heap->key($value)

Calculates the key corresponding to $value in the same way as the internals of $heap would. Can fail for Object and Any element types if there was no method or function given on heap creation.

Notice that this does not access the elements in the heap in any way. In particular, it's not looking for $value in the heap hoping to match its key.

$user_data = $heap->user_data

Queries the user_data associated with the heap.

$old_data = $heap->user_data($new_data)

Associates new user_data with the heap. Returns the old value.

$infinity = $heap->infinity

Queries the infinity value associated with the heap. Returns undef if there is none. The default infinity is implied by the chosen order relation.

$old_infinity = $heap->infinity($new_infinity)

Associates a new infinity with the heap. Returns the old value.

$key_index = $heap->key_index

Returns the index of the key for array reference based heaps. Doesn't exist for the other heap types.

$key_name = $heap->key_name

Returns the name of the key key for hash reference based heaps. Doesn't exist for the other heap types.

$key_name = $heap->key_method

Returns the name of the method to fetch the key from an object. Only exists for Method and Object based heaps.

$key_function = $heap->key_function

Returns the code reference of the function to fetch the key from an element. Only exists for "Function" and "Any" heaps.

$wrapped => $heap->wrapped

Returns true if key and value are stored seperately (wrapped together in some internal container), nothing otherwise. This is the sufficient and necessary condition for key_insert to work, and will normally only be true for the "Any" and Object type heaps.

$max_count => $heap->max_count

Returns the maximum size of the heap, or infinity if there is no maximum (the default unless you used the max_count option).

$can_die = $heap->can_die

Returns the can_die setting for this heap.

$dirty = $heap->dirty

Returns the dirty setting for this heap.

$order = $heap->order

Returns the order setting for this heap (either "<", ">", "lt", "gt" or a code reference).

@elements = $heap->elements

Returns the elements setting for this heap. The first entry in the returned list is a string representing the type in canonical form ("Scalar" or "Array" etc) followed by any arguments that type needed (e.g. the key name for a Hash type).

$elements = $heap->elements

Like the list context version, but only returns the first entry (the canonical type name).

$heap->absorb(@heaps)

Takes all elements from each heap in @heaps and inserts them in $heap, leaving each heap in @heaps empty. Behaves a bit like:

    for my $work_heap (@heaps) {
        $heap->insert(reverse $work_heap->values);
        $work_heap->clear;
    }

except that it may be more efficient.

If an exception is possible and gets raised during insert, the heaps will be left in a consistent state with a partial transfer completed on the condition that can_die is set for $heap (the settings for the heaps in @heaps are irrelevant, their accesses will always be done in a safe way)

$heap->key_absorb(@heaps)

Takes all elements from each heap in @heaps and key_inserts them in $heap, leaving each heap in @heaps empty. Behaves a bit like:

    for my $work_heap (@heaps) {
        my @values = $work_heap->values;
        my @keys   = $work_heap->keys;
        $heap->key_insert(pop @keys, pop @values) while @values;
        $work_heap->clear;
    }

except that it's may be more efficient. This is mainly meant for transfer between wrapped heap types (Any and Object) since it avoids key recalculation. $heap must of course be a wrapped heap type.

If an exception is possible and gets raised during insert, all heaps will be left in a consistent state with a partial transfer completed on the condition that can_die is set for $heap (the setting for the heaps in @heaps are irrelevant, their accesses will always be done in a safe way)

my $merged_aref = $heap->merge_arrays($aref1, $aref2, ...)

This convenience function merges a sequence of references to already sorted arrays into a new sorted array and returns its reference. So it does something like

    $merge_aref = [sort { $heap->compare_function->($a, $b) } map @$_, @_;
    shift @$merge_aref until @$merge_aref <= $heap->max_count;

except that it's more efficient (e.g. it uses the knowledge that the argument arrays are already sorted).

It leaves values stored in the $heap completely untouched. $heap is only used for its attributes: how to find the key, what the compare function is and the maximum number of elements.

$implementation = Heap::Simple->implementation

Returns the package that does the actual work. That will probably be "Heap::Simple::XS" or "Heap::Simple::Perl".

SEE ALSO ^

Heap::Simple::Perl, Heap::Simple::XS

Some other heap or heap-like classes that exist:

Heap, Heap::Priority, Array::Heap2

AUTHOR ^

Ton Hospel, <Heap-Simple@ton.iguana.be>

COPYRIGHT AND LICENSE ^

Copyright 2003 by Ton Hospel

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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