Class: Maybe

Inherits:
Object
  • Object
show all
Defined in:
lib/maybe.rb

Instance Method Summary collapse

Constructor Details

#initialize(value) ⇒ Maybe

Returns a new instance of Maybe.


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# File 'lib/maybe.rb', line 9

def initialize(value)
  @value = value
  self.join
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method_name, *args) ⇒ Object 


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# File 'lib/maybe.rb', line 14

def method_missing(method_name, *args)
  self.fmap do |value|
    value.send(method_name,*args) do |*block_args|
      yield(*block_args) if block_given?
    end
  end
end

Instance Method Details

#fmap ⇒ Object

Given that the value is of type A takes a function from A->B and returns M (a monad with a value of type B)


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# File 'lib/maybe.rb', line 40

def fmap
  if(@value==nil)
    self
  else
    Maybe.new(yield(@value))
  end
end

#join ⇒ Object 


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# File 'lib/maybe.rb', line 52

def join
  if(@value.is_a?(Maybe))
    @value = value.value
  end
  self
end

#nil? ⇒ Boolean

Returns:

  • (Boolean) 

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# File 'lib/maybe.rb', line 48

def nil?
  @value==nil
end

#pass ⇒ Object

Given that the value is of type A takes a function from A->M and returns M (a monad with a value of type B)


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# File 'lib/maybe.rb', line 33

def pass
  fmap {|*block_args| yield(*block_args)}.join
end

#value(value_if_nil = nil) ⇒ Object 


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# File 'lib/maybe.rb', line 22

def value(value_if_nil=nil)
  if(value_if_nil!=nil && @value==nil)
    value_if_nil
  else
    @value
  end
end

#value=(value) ⇒ Object

for testing purposes


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# File 'lib/maybe.rb', line 60

def value=(value)
  @value = value
end