    {-
    (c) The University of Glasgow 2006
    (c) The GRASP/AQUA Project, Glasgow University, 1998
    -}

    {-# LANGUAGE CPP #-}
    module NameSet (
            -- * Names set type
            NameSet,

            -- ** Manipulating these sets
            emptyNameSet, unitNameSet, mkNameSet, unionNameSet, unionNameSets,
            minusNameSet, elemNameSet, nameSetElems, extendNameSet, extendNameSetList,
            delFromNameSet, delListFromNameSet, isEmptyNameSet, foldNameSet, filterNameSet,
            intersectsNameSet, intersectNameSet,

            -- * Free variables
            FreeVars,

            -- ** Manipulating sets of free variables
            isEmptyFVs, emptyFVs, plusFVs, plusFV,
            mkFVs, addOneFV, unitFV, delFV, delFVs,

            -- * Defs and uses
            Defs, Uses, DefUse, DefUses,

            -- ** Manipulating defs and uses
            emptyDUs, usesOnly, mkDUs, plusDU,
            findUses, duDefs, duUses, allUses
        ) where

    #include "HsVersions.h"

    import Name
    import UniqSet

    {-
    ************************************************************************
    *                                                                      *
    \subsection[Sets of names}
    *                                                                      *
    ************************************************************************
    -}

    type NameSet = UniqSet Name

    emptyNameSet       :: NameSet
    unitNameSet        :: Name -> NameSet
    extendNameSetList   :: NameSet -> [Name] -> NameSet
    extendNameSet    :: NameSet -> Name -> NameSet
    mkNameSet          :: [Name] -> NameSet
    unionNameSet      :: NameSet -> NameSet -> NameSet
    unionNameSets  :: [NameSet] -> NameSet
    minusNameSet       :: NameSet -> NameSet -> NameSet
    elemNameSet        :: Name -> NameSet -> Bool
    nameSetElems      :: NameSet -> [Name]
    isEmptyNameSet     :: NameSet -> Bool
    delFromNameSet     :: NameSet -> Name -> NameSet
    delListFromNameSet :: NameSet -> [Name] -> NameSet
    foldNameSet        :: (Name -> b -> b) -> b -> NameSet -> b
    filterNameSet      :: (Name -> Bool) -> NameSet -> NameSet
    intersectNameSet   :: NameSet -> NameSet -> NameSet
    intersectsNameSet  :: NameSet -> NameSet -> Bool
    -- ^ True if there is a non-empty intersection.
    -- @s1 `intersectsNameSet` s2@ doesn't compute @s2@ if @s1@ is empty

    isEmptyNameSet    = isEmptyUniqSet
    emptyNameSet      = emptyUniqSet
    unitNameSet       = unitUniqSet
    mkNameSet         = mkUniqSet
    extendNameSetList  = addListToUniqSet
    extendNameSet   = addOneToUniqSet
    unionNameSet     = unionUniqSets
    unionNameSets = unionManyUniqSets
    minusNameSet      = minusUniqSet
    elemNameSet       = elementOfUniqSet
    nameSetElems     = uniqSetToList
    delFromNameSet    = delOneFromUniqSet
    foldNameSet       = foldUniqSet
    filterNameSet     = filterUniqSet
    intersectNameSet  = intersectUniqSets

    delListFromNameSet set ns = foldl delFromNameSet set ns

    intersectsNameSet s1 s2 = not (isEmptyNameSet (s1 `intersectNameSet` s2))

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Free variables}
    *                                                                      *
    ************************************************************************

    These synonyms are useful when we are thinking of free variables
    -}

    type FreeVars   = NameSet

    plusFV   :: FreeVars -> FreeVars -> FreeVars
    addOneFV :: FreeVars -> Name -> FreeVars
    unitFV   :: Name -> FreeVars
    emptyFVs :: FreeVars
    plusFVs  :: [FreeVars] -> FreeVars
    mkFVs    :: [Name] -> FreeVars
    delFV    :: Name -> FreeVars -> FreeVars
    delFVs   :: [Name] -> FreeVars -> FreeVars

    isEmptyFVs :: NameSet -> Bool
    isEmptyFVs  = isEmptyNameSet
    emptyFVs    = emptyNameSet
    plusFVs     = unionNameSets
    plusFV      = unionNameSet
    mkFVs       = mkNameSet
    addOneFV    = extendNameSet
    unitFV      = unitNameSet
    delFV n s   = delFromNameSet s n
    delFVs ns s = delListFromNameSet s ns

    {-
    ************************************************************************
    *                                                                      *
                    Defs and uses
    *                                                                      *
    ************************************************************************
    -}

    -- | A set of names that are defined somewhere
    type Defs = NameSet

    -- | A set of names that are used somewhere
    type Uses = NameSet

    -- | @(Just ds, us) =>@ The use of any member of the @ds@
    --                      implies that all the @us@ are used too.
    --                      Also, @us@ may mention @ds@.
    --
    -- @Nothing =>@ Nothing is defined in this group, but
    --              nevertheless all the uses are essential.
    --              Used for instance declarations, for example
    type DefUse  = (Maybe Defs, Uses)

    -- | A number of 'DefUse's in dependency order: earlier 'Defs' scope over later 'Uses'
    --   In a single (def, use) pair, the defs also scope over the uses
    type DefUses = [DefUse]

    emptyDUs :: DefUses
    emptyDUs = []

    usesOnly :: Uses -> DefUses
    usesOnly uses = [(Nothing, uses)]

    mkDUs :: [(Defs,Uses)] -> DefUses
    mkDUs pairs = [(Just defs, uses) | (defs,uses) <- pairs]

    plusDU :: DefUses -> DefUses -> DefUses
    plusDU = (++)

    duDefs :: DefUses -> Defs
    duDefs dus = foldr get emptyNameSet dus
      where
        get (Nothing, _u1) d2 = d2
        get (Just d1, _u1) d2 = d1 `unionNameSet` d2

    allUses :: DefUses -> Uses
    -- ^ Just like 'duUses', but 'Defs' are not eliminated from the 'Uses' returned
    allUses dus = foldr get emptyNameSet dus
      where
        get (_d1, u1) u2 = u1 `unionNameSet` u2

    duUses :: DefUses -> Uses
    -- ^ Collect all 'Uses', regardless of whether the group is itself used,
    -- but remove 'Defs' on the way
    duUses dus = foldr get emptyNameSet dus
      where
        get (Nothing,   rhs_uses) uses = rhs_uses `unionNameSet` uses
        get (Just defs, rhs_uses) uses = (rhs_uses `unionNameSet` uses)
                                         `minusNameSet` defs

    findUses :: DefUses -> Uses -> Uses
    -- ^ Given some 'DefUses' and some 'Uses', find all the uses, transitively.
    -- The result is a superset of the input 'Uses'; and includes things defined
    -- in the input 'DefUses' (but only if they are used)
    findUses dus uses
      = foldr get uses dus
      where
        get (Nothing, rhs_uses) uses
            = rhs_uses `unionNameSet` uses
        get (Just defs, rhs_uses) uses
            | defs `intersectsNameSet` uses         -- Used
            || any (startsWithUnderscore . nameOccName) (nameSetElems defs)
                    -- At least one starts with an "_",
                    -- so treat the group as used
            = rhs_uses `unionNameSet` uses
            | otherwise     -- No def is used
            = uses