role Mixy

Collection of distinct objects with Real weights

role Mixy does Baggy { }

A role for collections of weighted values. See Mix and MixHash. Mixy objects differ from Baggy objects in that the weights of Mixy are Reals rather than Ints.

Methods

method total

method total(--> Real)

Returns the sum of all the weights

mix('a', 'b', 'c', 'a', 'a', 'd').total == 6; # True
{a => 5.6, b => 2.4}.Mix.total == 8; # True

method roll

method roll($count = 1)

Similar to a Bag.roll, but with Real weights rather than integral ones.

See Also

Sets, Bags, and Mixes

Type graph

Type relations for Mixy
perl6-type-graph Mixy Mixy Baggy Baggy Mixy->Baggy Associative Associative QuantHash QuantHash QuantHash->Associative Baggy->QuantHash Mu Mu Any Any Any->Mu MixHash MixHash MixHash->Mixy MixHash->Any Mix Mix Mix->Mixy Mix->Any

Stand-alone image: vector, raster

Routines supplied by role Baggy

Mixy does role Baggy, which provides the following methods:

method grab

Defined as:

multi method grab(Baggy:D:) returns Any
multi method grab(Baggy:D: $count) returns Array:D

Like pick, a grab returns a random selection of elements, weighted by the values corresponding to each key. Unlike pick, it works only on mutable structures, e.g. BagHash. Use of grab on an immutable structure results in an X::Immutable exception. If * is passed as $count, or $count is greater than or equal to the total of the invocant, then total elements from the invocant are returned in a random sequence.

Grabbing decrements the grabbed key's weight by one (deleting the key when it reaches 0). By definition, the total of the invocant also decreases by one, so the probabilities stay consistent through subsequent grab operations.

my $cars = ('Ford' => 2, 'Rover' => 3).BagHash;
say $cars.grab;                                   # Ford
say $cars.grab(2);                                # [Rover Rover]
say $cars.grab(*);                                # [Rover Ford]

my $breakfast = ('eggs' => 2, 'bacon' => 3).Bag;
say $breakfast.grab;                              # throws X::Immutable exception

method grabpairs

Defined as:

multi method grabpairs(Baggy:D:) returns Any
multi method grabpairs(Baggy:D: $count) returns List:D

Returns a Pair or a List of Pairs depending on the version of the method being invoked. Each Pair returned has an element of the invocant as its key and the elements weight as its value. Unlike pickpairs, it works only on mutable structures, e.g. BagHash. Use of grabpairs on 'an immutable structure results in an X::Immutable exception. If * is passed as $count, or $count is greater than or equal to the number of elements of the invocant, then all element/weight Pairs from the invocant are returned in a random sequence.

What makes grabpairs different from pickpairs is that the 'grabbed' elements are in fact removed from the invocant.

my $breakfast = (eggs => 2, bacon => 3).BagHash;
say $breakfast.grabpairs;                         # bacon => 3
say $breakfast;                                   # BagHash.new(eggs(2))
say $breakfast.grabpairs(1);                      # (eggs => 2)
say $breakfast.grabpairs(*);                      # []

my $diet = ('eggs' => 2, 'bacon' => 3).Bag;
say $diet.grabpairs;                              # throws X::Immutable exception

method pick

Defined as:

multi method pick(Baggy:D:) returns Any
multi method pick(Baggy:D: $count) returns Seq:D

Like an ordinary list pick, but returns keys of the invocant weighted by their values, as if the keys were replicated the number of times indicated by the corresponding value and then list pick used. The underlying metaphor for picking is that you're pulling colored marbles out a bag. (For "picking with replacement" see roll instead). If * is passed as $count, or $count is greater than or equal to the total of the invocant, then total elements from the invocant are returned in a random sequence.

Note that each pick invocation maintains its own private state and has no effect on subsequent pick invocations.

my $breakfast = bag <eggs bacon bacon bacon>;
say $breakfast.pick;                              # eggs
say $breakfast.pick(2);                           # (eggs bacon)

say $breakfast.total;                             # 4
say $breakfast.pick(*);                           # (bacon bacon bacon eggs)

method pickpairs

Defined as:

multi method pickpairs(Baggy:D:) returns Pair:D
multi method pickpairs(Baggy:D: $count) returns List:D

Returns a Pair or a List of Pairs depending on the version of the method being invoked. Each Pair returned has an element of the invocant as its key and the elements weight as its value. The elements are 'picked' without replacement. If * is passed as $count, or $count is greater than or equal to the number of elements of the invocant, then all element/weight Pairs from the invocant are returned in a random sequence.

Note that each pickpairs invocation maintains its own private state and has no effect on subsequent pickpairs invocations.

my $breakfast = bag <eggs bacon bacon bacon>;
say $breakfast.pickpairs;                         # eggs => 1
say $breakfast.pickpairs(1);                      # (bacon => 3)
say $breakfast.pickpairs(*);                      # (eggs => 1 bacon => 3)

method roll

Defined as:

multi method roll(Baggy:D:) returns Any:D
multi method roll(Baggy:D: $count) returns Seq:D

Like an ordinary list roll, but returns keys of the invocant weighted by their values, as if the keys were replicated the number of times indicated by the corresponding value and then list roll used. The underlying metaphor for rolling is that you're throwing $count dice that are independent of each other, which (in bag terms) is equivalent to picking a colored marble out your bag and then putting it back, and doing this $count times. In dice terms, the number of marbles corresponds to the number of sides, and the number of marbles of the same color corresponds to the number of sides with the same color. (For "picking without replacement" see pick instead).

If * is passed to $count, returns a lazy, infinite sequence of randomly chosen elements from the invocant.

my $breakfast = bag <eggs bacon bacon bacon>;
say $breakfast.roll;                                  # bacon
say $breakfast.roll(3);                               # (bacon eggs bacon)

my $random_dishes := $breakfast.roll(*);
say $random_dishes[^5];                               # (bacon eggs bacon bacon bacon)

method pairs

Defined as:

method pairs(Baggy:D:) returns Seq:D

Returns all elements and their respective weights as a Seq of Pairs where the key is the element itself and the value is the weight of that element.

my $breakfast = bag <bacon eggs bacon>;
my $seq = $breakfast.pairs;
say $seq.sort;                                    # (bacon => 2 eggs => 1)

method antipairs

Defined as:

method antipairs(Baggy:D:) returns Seq:D

Returns all elements and their respective weights as a Seq of Pairs, where the element itself is the value and the weight of that element is the key, i.e. the opposite of method pairs.

my $breakfast = bag <bacon eggs bacon>;
my $seq = $breakfast.antipairs;
say $seq.sort;                                    # (1 => eggs 2 => bacon)

method invert

Defined as:

method invert(Baggy:D:) returns Seq:D

Returns all elements and their respective weights as a Seq of Pairs, where the element itself is the value and the weight of that element is the key, i.e. the opposite of method pairs. Except for some esoteric cases invert on a Baggy type returns the same result as antipairs.

my $breakfast = bag <bacon eggs bacon>;
my $seq = $breakfast.invert;
say $seq.sort;                                    # (1 => eggs 2 => bacon)

method classify-list

Defined as:

multi method classify-list(&test, *@list) returns Baggy:D

Transforms a list of values into a classification of those values according to &test and stores the results in the invocant which is then returned. Each key represents the classification for one or more of the incoming list values, and the corresponding value contains the number of list values classified by &test into the category of the associated key.

As an example, suppose that we have a list of Ints which we would like to classify into two categories, namely even and odd numbers. Here's one way to solve this problem:

my $b = BagHash.new();
dd $b.classify-list( { $_ %% 2 ?? 'even' !! 'odd' }, (1, 7, 6, 3, 2) );
# returns: ("even"=>2,"odd"=>3).BagHash

The printed result shows us that of the numbers in the list two were classified as even and three as odd. Note that the result doesn't show us which numbers were classified as being even or odd. If that's what you want, use the classify routine in List instead.

method categorize-list

method keys

Defined as:

method keys(Baggy:D:) returns List:D

Returns a list of all keys in the Baggy object without taking their individual weights into account as opposed to kxxv.

my $breakfast = bag <eggs spam spam spam>;
say $breakfast.keys.sort;                        # (eggs spam)

my $n = ("a" => 5, "b" => 2).BagHash;
say $n.keys.sort;                                # (a b)

method values

Defined as:

method values(Baggy:D:) returns List:D

Returns a list of all values, i.e. weights, in the Baggy object.

my $breakfast = bag <eggs spam spam spam>;
say $breakfast.values.sort;                      # (1 3)

my $n = ("a" => 5, "b" => 2, "a" => 1).BagHash;
say $n.values.sort;                              # (2 6)

method kv

Defined as:

method kv(Baggy:D:) returns List:D

Returns a list of keys and values interleaved.

my $breakfast = bag <eggs spam spam spam>;
say $breakfast.kv;                                # (spam 3 eggs 1)

my $n = ("a" => 5, "b" => 2, "a" => 1).BagHash;
say $n.kv;                                        # (a 6 b 2)

method kxxv

Defined as:

method kxxv(Baggy:D:) returns List:D

Returns a list of the keys of the invocant, with each key multiplied by its weight. Note that kxxv only works for Baggy types which have integer weights, i.e. Bag and BagHash.

my $breakfast = bag <spam eggs spam spam bacon>;
say $breakfast.kxxv.sort;                         # (bacon eggs spam spam spam)

my $n = ("a" => 0, "b" => 1, "b" => 2).BagHash;
say $n.kxxv;                                      # (b b b)

method elems

Defined as:

method elems(Baggy:D:) returns Int:D

Returns the number of elements in the Baggy object without taking the individual elements weight into account.

my $breakfast = bag <eggs spam spam spam>;
say $breakfast.elems;                             # 2

my $n = ("b" => 9.4, "b" => 2).MixHash;
say $n.elems;                                     # 1

method total

Defined as:

method total(Baggy:D:)

Returns the sum of weights for all elements in the Baggy object.

my $breakfast = bag <eggs spam spam bacon>;
say $breakfast.total;                             # 4

my $n = ("a" => 5, "b" => 1, "b" => 2).BagHash;
say $n.total;                                     # 8

method default

Defined as:

method default(Baggy:D:) returns Int:D

Returns zero.

my $breakfast = bag <eggs bacon>;
say $breakfast.default;                           # 0

method hash

Defined as:

method hash(Baggy:D:) returns Hash:D

Returns a Hash where the elements of the invocant are the keys and their respective weights the values;

my $breakfast = bag <eggs bacon bacon>;
my $h = $breakfast.hash;
say $h.WHAT;                                      # (Hash)
say $h;                                           # {bacon => 2, eggs => 1}

method Bool

Defined as:

method Bool(Baggy:D:) returns Bool:D

Returns True if the invocant contains at least one element.

my $breakfast = ('eggs' => 1).BagHash;
say $breakfast.Bool;                              # True   (since we have one element)
$breakfast<eggs> = 0;                             # weight == 0 will lead to element removal
say $breakfast.Bool;                              # False

method Set

Defined as:

method Set() returns Set:D

Returns a Set whose elements are the keys of the invocant.

my $breakfast = (eggs => 2, bacon => 3).BagHash;
say $breakfast.Set;                               # set(bacon, eggs)

method SetHash

Defined as:

method SetHash() returns SetHash:D

Returns a SetHash whose elements are the keys of the invocant.

my $breakfast = (eggs => 2, bacon => 3).BagHash;
my $sh = $breakfast.SetHash;
say $sh.WHAT;                                     # (SetHash)
say $sh.elems;                                    # 2

method ACCEPTS

Defined as:

method ACCEPTS($other) returns Bool:D

Used in smart-matching if the right-hand side is a Baggy.

If the right hand side is the type object, i.e. Baggy, the method returns True if $other does Baggy otherwise False is returned.

If the right hand side is a Baggy object, True is returned only if $other has the same elements, with the same weights, as the invocant.

my $breakfast = bag <eggs bacon>;
say $breakfast ~~ Baggy;                            # True
say $breakfast.does(Baggy);                         # True

my $second-breakfast = (eggs => 1, bacon => 1).Mix;
say $breakfast ~~ $second-breakfast;                # True

my $third-breakfast = (eggs => 1, bacon => 2).Bag;
say $second-breakfast ~~ $third-breakfast;          # False