Maintainer	[email protected]
Safe Haskell	Safe-Infered

Data.Monoid.Split

Description

Sometimes we want to accumulate values from some monoid, but have the ability to introduce a "split" which separates values on either side. For example, in the diagrams graphics framework this is used when accumulating transformations to be applied to primitive diagrams: the freeze operation introduces a split, since only transformations occurring outside the freeze should be applied to attributes.

Synopsis

Documentation

data Split m Source

A value of type Split m is either a single m, or a pair of m's separated by a divider.

Constructors

M m
m :\| m

Instances

(Semigroup m, Monoid m) => Monoid (Split m)
Semigroup m => Semigroup (Split m)	If `m` is a `Semigroup`, then `Split m` is a semigroup which combines values on either side of a split, keeping only the rightmost split.
Action m n => Action (Split m) n	By default, the action of a split monoid is the same as for the underlying monoid, as if the split were removed.

split :: Monoid m => Split mSource

A convenient name for mempty :| mempty, so a <> split <> b == a :| b.

unsplit :: Semigroup m => Split m -> mSource

"Unsplit" a split monoid value, combining the two values into one (or returning the single value if there is no split).