module

Enumerable(T)

The Enumerable mixin provides collection classes with several traversal, searching, filtering and querying methods.

Including types must provide an each method, which yields successive members of the collection.

For example:

class Three
  include Enumerable(Int32)

  def each(&)
    yield 1
    yield 2
    yield 3
  end
end

three = Three.new
three.to_a                # => [1, 2, 3]
three.select &.odd?       # => [1, 3]
three.all? { |x| x < 10 } # => true

Note that most search and filter methods traverse an Enumerable eagerly, producing an Array as the result. For a lazy alternative refer to the Iterator and Iterable modules.

Instance methods

average(weights : Indexable(Number))

Returns the weighted average of the elements in the collection. Raises EmptyError if the collection is empty or ArgumentError if weights has a different number of elements.

Expects all element types to respond to #+ and #/ methods.

[1, 2, 3, 4, 5, 6].average((1..6).to_a) # => 4.333333333333333
(1..6).average((1..6).to_a)             # => 4.333333333333333
([] of Int32).average([1, 1, 1])        # raises EmptyError
(1..6).average([1, 1])                  # raises ArgumentError

NOTE: This method calls .additive_identity on the element type and weights' element type to determine the type of the intermediate sum values.

Source
average(weights : Indexable(Number), & : T -> _)

Returns the weighted average of the results of the passed block for each element in the collection. Raises EmptyError if the collection is empty or ArgumentError if weights has a different number of elements.

Expects all element types to respond to #+ and #/ methods.

["Alice", "Bob"].average([7, 2], &.size)    # => 4.555555555555555
('a'..'z').average((0..25).to_a, &.ord)     # => 4.333333333333333
([] of String).average([1, 1], &.size)      # raises EmptyError
["Alice", "Bob"].average([1, 1, 1], &.size) # raises ArgumentError

NOTE: This method calls .additive_identity on the yielded type and weights' element type to determine the type of the intermediate sum values.

Source
mean

Returns the arithmetic mean of the elements in the collection. Raises EmptyError if the collection is empty.

Expects all element types to respond to #+ and #/ methods.

[1, 2, 3, 4, 5, 6].mean # => 3.5
(1..6).mean             # => 3.5
([] of Int32).mean      # raises EmptyError

NOTE: This method calls .additive_identity on the element type to determine the type of the intermediate sum.

Source
mean

Returns the arithmetic mean of the results of the passed block for each element in the collection. Raises EmptyError if the collection is empty.

Expects all element types to respond to #+ and #/ methods.

["Alice", "Bob"].mean(&.size) # => 4
('a'..'z').mean(&.ord)        # => 109.5
([] of String).mean(&.size)   # raises EmptyError

NOTE: This method calls .additive_identity on the yielded type to determine the type of the intermediate sum.

Source