| Copyright | (c) Uli Köhler 2014 |
|---|---|
| License | Apache License v2.0 |
| Maintainer | ukoehler@techoverflow.net |
| Stability | provisional |
| Portability | portable |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Control.GroupWith
Description
A collection of grouping utility functions. For a given function that assigns a key to objects, provides functions that group said objects into a multimap by said key.
This can be used similarly to the SQL GROUP BY statement.
Provides a more flexible approach to GHC.Exts.groupWith
groupWith (take 1) ["a","ab","bc"] == Map.fromList [("a",["a","ab"]), ("b",["bc"])]Documentation
Arguments
| :: Ord b | |
| => (a -> b) | The function used to map a list value to its key |
| -> [a] | The list to be grouped |
| -> MultiMap b a | The resulting key --> value multimap |
Group values in a list by a key, generated by a given function. The resulting map contains for each generated key the values (from the given list) that yielded said key by applying the function on said value.
Arguments
| :: Ord b | |
| => (a -> [b]) | The function used to map a list value to its keys |
| -> [a] | The list to be grouped |
| -> MultiMap b a | The resulting map |
Like groupWith, but the identifier-generating function may generate multiple keys for each value (or none at all). The corresponding value from the original list will be placed in the identifier-corresponding map entry for each generated identifier. Note that values are added to the
Arguments
| :: Ord b | |
| => (a -> c) | Transformer function used to map a value to the resulting type |
| -> (c -> c -> c) | The combinator used to combine an existing value for a given key with a new value |
| -> (a -> b) | The function used to map a list value to its key |
| -> [a] | The list to be grouped |
| -> Map b c | The resulting key --> transformed value map |
Like groupWith, but uses a custom combinator function