GHC.Types.Unique.SDFM

ghc-9.2.0.20210331: The GHC API

Safe Haskell | Safe-Inferred
Language | Haskell2010

GHC.Types.Unique.SDFM

Contents

- Unique-keyed, shared, deterministic mappings

Description

Like a `UniqDFM`, but maintains equivalence classes of keys sharing the same entry. See `UniqSDFM`.

Synopsis

- data UniqSDFM key ele
- emptyUSDFM :: UniqSDFM key ele
- lookupUSDFM :: Uniquable key => UniqSDFM key ele -> key -> Maybe ele
- equateUSDFM :: Uniquable key => UniqSDFM key ele -> key -> key -> (Maybe ele, UniqSDFM key ele)
- addToUSDFM :: Uniquable key => UniqSDFM key ele -> key -> ele -> UniqSDFM key ele
- traverseUSDFM :: forall key a b f. Applicative f => (a -> f b) -> UniqSDFM key a -> f (UniqSDFM key b)

# Unique-keyed, shared, deterministic mappings

data UniqSDFM key ele Source #

A `UniqDFM` whose domain is sets of `Unique`s, each of which share a common value of type `ele`. Every such set ("equivalence class") has a distinct representative `Unique`. Supports merging the entries of multiple such sets in a union-find like fashion.

An accurate model is that of `[(Set key, Maybe ele)]`: A finite mapping from sets of `key`s to possibly absent entries `ele`, where the sets don't overlap. Example: `m = [({u1,u3}, Just ele1), ({u2}, Just ele2), ({u4,u7}, Nothing)]` On this model we support the following main operations:

- ``lookupUSDFM` m u3 == Just ele1`, ``lookupUSDFM` m u4 == Nothing`, ``lookupUSDFM` m u5 == Nothing`.
- ``equateUSDFM` m u1 u3` is a no-op, but ``equateUSDFM` m u1 u2` merges `{u1,u3}` and `{u2}` to point to `Just ele2` and returns the old entry of `{u1,u3}`, `Just ele1`.
- ``addToUSDFM` m u3 ele4` sets the entry of `{u1,u3}` to `Just ele4`.

As well as a few means for traversal/conversion to list.

#### Instances

Instances details

(Outputable key, Outputable ele) => Outputable (UniqSDFM key ele) # |
Instance details Defined in GHC.Types.Unique.SDFM Methods ppr :: UniqSDFM key ele -> SDoc Source #

emptyUSDFM :: UniqSDFM key ele Source #

lookupUSDFM :: Uniquable key => UniqSDFM key ele -> key -> Maybe ele Source #

`lookupSUDFM env x` looks up an entry for `x`, looking through all `Indirect`s until it finds a shared `Entry`.

Examples in terms of the model (see `UniqSDFM`): >>> lookupUSDFM [({u1,u3}, Just ele1), ({u2}, Just ele2)] u3 == Just ele1 >>> lookupUSDFM [({u1,u3}, Just ele1), ({u2}, Just ele2)] u4 == Nothing >>> lookupUSDFM [({u1,u3}, Just ele1), ({u2}, Nothing)] u2 == Nothing

equateUSDFM :: Uniquable key => UniqSDFM key ele -> key -> key -> (Maybe ele, UniqSDFM key ele) Source #

`equateUSDFM env x y` makes `x` and `y` point to the same entry, thereby merging `x`'s class with `y`'s. If both `x` and `y` are in the domain of the map, then `y`'s entry will be chosen as the new entry and `x`'s old entry will be returned.

Examples in terms of the model (see `UniqSDFM`): >>> equateUSDFM [] u1 u2 == (Nothing, [({u1,u2}, Nothing)]) >>> equateUSDFM [({u1,u3}, Just ele1)] u3 u4 == (Nothing, [({u1,u3,u4}, Just ele1)]) >>> equateUSDFM [({u1,u3}, Just ele1)] u4 u3 == (Nothing, [({u1,u3,u4}, Just ele1)]) >>> equateUSDFM [({u1,u3}, Just ele1), ({u2}, Just ele2)] u3 u2 == (Just ele1, [({u2,u1,u3}, Just ele2)])

addToUSDFM :: Uniquable key => UniqSDFM key ele -> key -> ele -> UniqSDFM key ele Source #

`addToUSDFM env x a` sets the entry `x` is associated with to `a`, thereby modifying its whole equivalence class.

Examples in terms of the model (see `UniqSDFM`): >>> addToUSDFM [] u1 ele1 == [({u1}, Just ele1)] >>> addToUSDFM [({u1,u3}, Just ele1)] u3 ele2 == [({u1,u3}, Just ele2)]

traverseUSDFM :: forall key a b f. Applicative f => (a -> f b) -> UniqSDFM key a -> f (UniqSDFM key b) Source #