Module: Immutable::Foldable

Included in:
Headable, Map
Defined in:
lib/immutable/foldable.rb

Instance Method Summary collapse

Instance Method Details

#foldl(e, &block) ⇒ Object

Reduces self using block from left to right. e is used as the starting value. A class including Immutable::Foldable must implement this method.

Parameters:

  • e (Object) —

    the start value.

Returns:

  • (Object) —

    the reduced value.

Raises:

  • (NotImplementedError) 


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# File 'lib/immutable/foldable.rb', line 9

def foldl(e, &block)
  raise NotImplementedError
end

#length ⇒ Integer Also known as: size

Returns the number of elements in self. May be zero.

Returns:

  • (Integer) —

    the number of elements in self.



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# File 'lib/immutable/foldable.rb', line 16

def length
  foldl(0) { |x, y| x + 1 }
end

#product ⇒ #*

Computes the product of the numbers in self.

Returns:

  • (#*) —

    the product of the numbers.



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# File 'lib/immutable/foldable.rb', line 35

def product
  foldl(1) { |x, y| x * y }
end

#sum ⇒ #+

Computes the sum of the numbers in self.

Returns:

  • (#+) —

    the sum of the numbers.



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# File 'lib/immutable/foldable.rb', line 28

def sum
  foldl(0) { |x, y| x + y }
end