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GHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05

Modulestrict-0.5.1Haskell2010

Data.Strict.Maybe

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.

  • 1 type
  • 9 values
  • Packagestrict-0.5.1
  • Exports10
  • LanguageHaskell2010
  • LicenceBSD-3-Clause
  • SourceMaybe.hs
datadata Maybe a
#

The type of strict optional values.

Constructors

Instances24Functor, Foldable, Traversable, Eq1, Ord1, Read1, …
valuefromMaybe :: a -> Maybe a -> a
#

Given a default value and a Maybe, yield the default value if the Maybe argument is Nothing and extract the value out of the Just otherwise.

valuemaybe :: b -> (a -> b) -> Maybe a -> b
#

Given a default value, a function and a Maybe value, yields the default value if the Maybe value is Nothing and applies the function to the value stored in the Just otherwise.