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1. orElse :: Maybe a -> a -> a

   ghc-lib-parser	GHC.Data.Maybe

   Flipped version of fromMaybe, useful for chaining.

2. orElse :: Parser x s a -> Parser e s a -> Parser e s a

   bytesmith	Data.Bytes.Parser

   There is a law-abiding instance of Alternative for Parser. However, it is not terribly useful since error messages seldom have a Monoid instance. This function is a variant of <|> that is right-biased in its treatment of error messages. Consequently, orElse lacks an identity. See attoparsec issue #122 for more discussion of this topic.

3. orElse :: (Selective f, Semigroup e) => f (Either e a) -> f (Either e a) -> f (Either e a)

   rebase	Rebase.Prelude

   Return the first Right value. If both are Left's, accumulate errors.

4. orElse :: STM a -> STM a -> STM a

   effectful	Effectful.Concurrent.STM

   Compose two alternative STM actions (GHC only). If the first action completes without retrying then it forms the result of the orElse. Otherwise, if the first action retries, then the second action is tried in its place. If both actions retry then the orElse as a whole retries.

5. orElse :: MonadSTM stm => stm a -> stm a -> stm a

   concurrency	Control.Monad.STM.Class

   Run the first transaction and, if it retrys, run the second instead. This is just mplus.

6. orElse :: Semigroup e => Validator e inp a -> Validator e inp a -> Validator e inp a

   valida	Valida.Combinators

   Build a validator that succeeds if either of the given validators succeed. The first (left-most) Success is returned. If both fail, the errors are combined. Other validator is not used if first one succeeds.

   vald1 `orElse` (vald2 `orElse` vald3) = (vald1 `orElse` vald2) `orElse` vald3
   

   failV e `orElse` vald = vald
   

   vald `orElse` failV e = vald
   

   Examples

   >>> let vald = failureIf (>0) "Positive" `orElse` failureIf even "Even"
   
   >>> runValidator vald 5
   Success 5
   
   >>> runValidator vald 4
   Failure ("Positive" :| ["Even"])
   
   >>> runValidator vald 0
   Success 0
   
   >>> runValidator vald (-1)
   Success (-1)
   

7. orElse :: Semigroup e => ValidationRule e a -> ValidationRule e a -> ValidationRule e a

   valida-base	Valida.Combinators

   Build a rule that succeeds if either of the given rules succeed. If both fail, the errors are combined.

   rule1 `orElse` (rule2 `orElse` rule3) = (rule1 `orElse` rule2) `orElse` rule3
   

   falseRule e `orElse` rule = rule
   

   rule `orElse` falseRule e = rule
   

   Examples

   >>> let rule = failureIf (>0) "Positive" `orElse` failureIf even "Even"
   
   >>> runValidator (validate rule) 5
   Success 5
   
   >>> runValidator (validate rule) 4
   Failure ("Positive" :| ["Even"])
   
   >>> runValidator (validate rule) 0
   Success 0
   
   >>> runValidator (validate rule) (-1)
   Success (-1)
   

8. orElse :: Validate v => v e a -> a -> a

   validation	Data.Validation

   v orElse a returns a when v is Failure, and the a in Success a. This can be thought of as having the less general type:

   orElse :: Validation e a -> a -> a
   

9. orElse :: STM a -> STM a -> STM a

   classy-prelude-yesod	ClassyPrelude.Yesod

   Compose two alternative STM actions (GHC only). If the first action completes without retrying then it forms the result of the orElse. Otherwise, if the first action retries, then the second action is tried in its place. If both actions retry then the orElse as a whole retries.

10. orElseSTM :: STM a -> STM a -> STM a

    classy-prelude	ClassyPrelude

    Synonym for orElse.

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