appendmap
Map with a Semigroup and Monoid instances delegating to Semigroup of the elements
https://github.com/koterpillar/appendmap#readme
| LTS Haskell 24.16: | 0.1.5 |
| Stackage Nightly 2025-10-24: | 0.1.5 |
| Latest on Hackage: | 0.1.5 |
Maintained by [email protected]
This version can be pinned in stack with:
appendmap-0.1.5@sha256:1c150f734016276c580de7064d620d86f4793603c0d5c7f2724c6b5f0fcaf316,1548Module documentation for 0.1.5
Depends on 2 packages(full list with versions):
appendmap
A Data.Map wrapper with a Semigroup and Monoid instances that delegate to
the individual keys.
import qualified Data.Map as Map
import Data.Map.Append
> one = AppendMap $ Map.fromList [(1, "hello"), (2, "goodbye")]
> two = AppendMap $ Map.fromList [(1, "world"), (3, "again")]
> unAppendMap (one <> two)
fromList [(1, "helloworld"), (2, "goodbye"), (3, "again")]
Motivation
Data.Map has a Semigroup instance that keeps the values from the first
argument in case of a key conflict:
import qualified Data.Map as Map
import Data.Map.Append
> Map.fromList [(1, "hello")] <> Map.fromList [(1, "goodbye")]
fromList [(1, "hello")]
A different instance has been suggested for a long time (1, 2), but this is a breaking change and hasn’t happened yet (as of 2018-08).
Development
Source code is formatted with hindent then stylish-haskell.
Releasing
- Run
./bumpversion patch|minor|major. This will create a new version and push it to the repository to be released.