Method: Fear::Either#get_or_else

Defined in:
lib/fear/either.rb

#get_or_else(&default) ⇒ any #get_or_else(default) ⇒ any

Returns the value from this Right or evaluates the given default argument if this is a Left.

Overloads:

  • #get_or_else(&default) ⇒ any

    Examples:

    Fear.right(42).get_or_else { 24/2 }         #=> 42
Fear.left('undefined').get_or_else { 24/2 } #=> 12

    Yield Returns:

    • (any)

    Returns:

    • (any)
  • #get_or_else(default) ⇒ any

    Examples:

    Fear.right(42).get_or_else(12)         #=> 42
Fear.left('undefined').get_or_else(12) #=> 12

    Returns:

    • (any) 


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# File 'lib/fear/either.rb', line 246

module Either
  # @private
  def left_class
    Left
  end

  # @private
  def right_class
    Right
  end

  def initialize(value)
    @value = value
  end

  attr_reader :value
  protected :value

  # @param other [Any]
  # @return [Boolean]
  def ==(other)
    other.is_a?(self.class) && value == other.value
  end

  # @return [String]
  def inspect
    "#<#{self.class} value=#{value.inspect}>"
  end

  # @return [String]
  alias_method :to_s, :inspect

  # @return [<any>]
  def deconstruct
    [value]
  end

  # Projects this +Fear::Either+ as a +Fear::Left+.
  # This allows performing right-biased operation of the left
  # side of the +Fear::Either+.
  #
  # @example
  #   Fear.left(42).left.map(&:succ)  #=> Fear.left(43)
  #   Fear.right(42).left.map(&:succ) #=> Fear.left(42)
  #
  # @return [Fear::LeftProjection]
  def left
    LeftProjection.new(self)
  end

  class << self
    # Build pattern matcher to be used later, despite off
    # +Either#match+ method, id doesn't apply matcher immanently,
    # but build it instead. Unusually in sake of efficiency it's better
    # to statically build matcher and reuse it later.
    #
    # @example
    #   matcher =
    #     Either.matcher do |m|
    #       m.right(Integer, ->(x) { x > 2 }) { |x| x * 2 }
    #       m.right(String) { |x| x.to_i * 2 }
    #       m.left(String) { :err }
    #       m.else { 'error '}
    #     end
    #   matcher.call(Fear.right(42))
    #
    # @yieldparam [Fear::Either::PatternMatch]
    # @return [Fear::PartialFunction]
    def matcher(&matcher)
      Either::PatternMatch.new(&matcher)
    end
  end

  # Include this mixin to access convenient factory methods.
  # @example
  #   include Fear::Either::Mixin
  #
  #   Right('flower') #=> #<Fear::Right value='flower'>
  #   Left('beaf')    #=> #<Fear::Legt value='beaf'>
  #
  module Mixin
    # @param value [any]
    # @return [Fear::Left]
    # @example
    #   Left(42) #=> #<Fear::Left value=42>
    #
    def Left(value)
      Fear.left(value)
    end

    # @param value [any]
    # @return [Fear::Right]
    # @example
    #   Right(42) #=> #<Fear::Right value=42>
    #
    def Right(value)
      Fear.right(value)
    end
  end
end