Module: Monadic

Defined in:
lib/monadic/try.rb,
lib/monadic/maybe.rb,
lib/monadic/monad.rb,
lib/monadic/either.rb,
lib/monadic/errors.rb,
lib/monadic/version.rb,
lib/monadic/validation.rb

Defined Under Namespace

Modules: Monad, SuccessFailure Classes: Either, Failure, Just, Maybe, NoValueError, NotEitherError, Nothing, Success, Validation

Constant Summary collapse

VERSION =
"0.8.1"

Instance Method Summary collapse

Instance Method Details

#Either(value) ⇒ Success, Failure

Coerces any value into either a Success or a Failure.

Returns:

  • (Success, Failure)

    depending whether value is falsey i.e. nil, false, Enumerable#empty? become Failure, all other `Success`


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# File 'lib/monadic/either.rb', line 138

def Either(value)
  Either.unit(value)
end

#Failure(value) ⇒ Object


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# File 'lib/monadic/either.rb', line 126

def Failure(value)
  Failure.new(value)
end

#Maybe(value) ⇒ Object Also known as: Just, Nothing


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# File 'lib/monadic/maybe.rb', line 122

def Maybe(value)
  Maybe.unit(value)
end

#Success(value) ⇒ Success

Factory method

Returns:


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# File 'lib/monadic/either.rb', line 132

def Success(value)
  Success.new(value)
end

#Try(arg = nil, &block) ⇒ Object

Wrap a block or a predicate to always return Success or Failure. It will catch StandardError and return as a Failure.


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# File 'lib/monadic/try.rb', line 4

def Try(arg = nil, &block)
  begin
    predicate = arg.is_a?(Proc) ? arg.call : arg
    return Either(block.call) if block_given? && predicate.nil?
    return Either(predicate).class.unit(block.call) if block_given?   # use predicate for Success/Failure and block for value
    return Either(predicate)
  rescue => error
    Failure(error)
  end
end

#Validation(&block) ⇒ Object

Wraps the construction of the Validation class


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# File 'lib/monadic/validation.rb', line 3

def Validation(&block)
  Validation.new.call(&block)
end