Alternative

A monoid on applicative functors. If defined, some and many should be the least solutions of the equations:

• some v = (:) <$> v <*>
  many v

• many v = some v <|> pure
  []

Examples

>>> Nothing <|> Just 42
Just 42

>>> [1, 2] <|> [3, 4]
[1,2,3,4]

>>> empty <|> print (2^15)
32768

A monoid on applicative functors. If defined, some and many should be the least solutions of the equations:

• some v = (:) <$> v <*>
  many v

• many v = some v <|> pure
  []

Alternative utilities. For instance, they can be applied with parsing libraries.

A semigroup for working with Alternative Functors.

Check Alternative Monoid laws

Multiple alternative representations of the same data. For example, you could provide a plain-text and HTML version of a message.

Undocumented parsing-related extensions introduced in GHC 7.0.

Undocumented parsing-related extensions introduced in GHC 7.0.

A GtkShortcutTrigger that combines two triggers. The GtkAlternativeTrigger triggers when either of two trigger. This can be cascaded to combine more than two triggers.

Memory-managed wrapper type.

Combines two shortcut triggers. The GtkAlternativeTrigger triggers when either of the two trigger. This can be cascaded to combine more than two triggers.

Internal state of the result of Alternative constructions

Try to deserialize each constructor of a in order. For sum types, stock Binary writes (and expects to read) an integer denoting the index of the constructor. This isn't always what's needed. In the following example, the constructor is uniquely identified by the marker byte, and its index in the Haskell ADT is irrelevant:

data JfifSegment
= App0Segment (MatchByte "app0 segment" 0xe0, JfifApp0)
| DqtSegment  (MatchByte "dqt segment"  0xdb, QuantTable)
| SofSegment  (MatchByte "sof segment"  0xc0, SofInfo)
| DhtSegment  (MatchByte "dht segment"  0xc4, HuffmanTable)
| DriSegment  (MatchByte "dri segment"  0xdd, RestartInterval)
| SosSegment  (MatchByte "sos segment"  0xda, SosImage)
| UnknownSegment RawSegment
deriving Generic
deriving Binary via Alternatively JfifSegment

Possible alternatives.