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Within LTS Haskell 22.18 (ghc-9.6.4)
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ghc GHC.Prelude.Basic The Maybe type encapsulates an optional value. A value of type Maybe a either contains a value of type a (represented as Just a), or it is empty (represented as Nothing). Using Maybe is a good way to deal with errors or exceptional cases without resorting to drastic measures such as error. The Maybe type is also a monad. It is a simple kind of error monad, where all errors are represented by Nothing. A richer error monad can be built using the Either type.
module Control.Monad.Trans.
Maybe No documentation available.
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No documentation available.
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haskell-gi-base Data.GI.Base.ShortPrelude The Maybe type encapsulates an optional value. A value of type Maybe a either contains a value of type a (represented as Just a), or it is empty (represented as Nothing). Using Maybe is a good way to deal with errors or exceptional cases without resorting to drastic measures such as error. The Maybe type is also a monad. It is a simple kind of error monad, where all errors are represented by Nothing. A richer error monad can be built using the Either type.
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rio RIO.Prelude.Types The Maybe type encapsulates an optional value. A value of type Maybe a either contains a value of type a (represented as Just a), or it is empty (represented as Nothing). Using Maybe is a good way to deal with errors or exceptional cases without resorting to drastic measures such as error. The Maybe type is also a monad. It is a simple kind of error monad, where all errors are represented by Nothing. A richer error monad can be built using the Either type.
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The strict variant of the standard Haskell Maybe type and the corresponding variants of the functions from Data.Maybe. Note that in contrast to the standard lazy Maybe type, the strict Maybe type is not an applicative functor, and therefore also not a monad. The problem is the homomorphism law, which states that
pure f <*> pure x = pure (f x) -- must hold for all f
This law does not hold for the expected applicative functor instance of Maybe, as this instance does not satisfy pure f <*> pure _|_ = pure (f _|_) for f = const. -
strict Data.Strict.Maybe The type of strict optional values.
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basement Basement.Compat.Base The Maybe type encapsulates an optional value. A value of type Maybe a either contains a value of type a (represented as Just a), or it is empty (represented as Nothing). Using Maybe is a good way to deal with errors or exceptional cases without resorting to drastic measures such as error. The Maybe type is also a monad. It is a simple kind of error monad, where all errors are represented by Nothing. A richer error monad can be built using the Either type.
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basement Basement.Imports The Maybe type encapsulates an optional value. A value of type Maybe a either contains a value of type a (represented as Just a), or it is empty (represented as Nothing). Using Maybe is a good way to deal with errors or exceptional cases without resorting to drastic measures such as error. The Maybe type is also a monad. It is a simple kind of error monad, where all errors are represented by Nothing. A richer error monad can be built using the Either type.
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Utility functions to work with Maybe data type as monad.