+++ /dev/null
-%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-%
-\section[ListSetOps]{Set-like operations on lists}
-
-\begin{code}
-module ListSetOps (
- unionLists, minusList, insertList,
-
- -- Association lists
- Assoc, assoc, assocMaybe, assocUsing, assocDefault, assocDefaultUsing,
- emptyAssoc, unitAssoc, mapAssoc, plusAssoc_C, extendAssoc_C,
- mkLookupFun, findInList, assocElts,
-
- -- Duplicate handling
- hasNoDups, runs, removeDups, findDupsEq,
- equivClasses, equivClassesByUniq
-
- ) where
-
-#include "HsVersions.h"
-
-import Outputable
-import Unique ( Unique )
-import UniqFM ( eltsUFM, emptyUFM, addToUFM_C )
-import Util ( isn'tIn, isIn, mapAccumR, sortLe )
-import List ( partition )
-\end{code}
-
-
-%************************************************************************
-%* *
- Treating lists as sets
- Assumes the lists contain no duplicates, but are unordered
-%* *
-%************************************************************************
-
-\begin{code}
-insertList :: Eq a => a -> [a] -> [a]
--- Assumes the arg list contains no dups; guarantees the result has no dups
-insertList x xs | isIn "insert" x xs = xs
- | otherwise = x : xs
-
-unionLists :: (Eq a) => [a] -> [a] -> [a]
--- Assumes that the arguments contain no duplicates
-unionLists xs ys = [x | x <- xs, isn'tIn "unionLists" x ys] ++ ys
-
-minusList :: (Eq a) => [a] -> [a] -> [a]
--- Everything in the first list that is not in the second list:
-minusList xs ys = [ x | x <- xs, isn'tIn "minusList" x ys]
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[Utils-assoc]{Association lists}
-%* *
-%************************************************************************
-
-Inefficient finite maps based on association lists and equality.
-
-\begin{code}
-type Assoc a b = [(a,b)] -- A finite mapping based on equality and association lists
-
-emptyAssoc :: Assoc a b
-unitAssoc :: a -> b -> Assoc a b
-assocElts :: Assoc a b -> [(a,b)]
-assoc :: (Eq a) => String -> Assoc a b -> a -> b
-assocDefault :: (Eq a) => b -> Assoc a b -> a -> b
-assocUsing :: (a -> a -> Bool) -> String -> Assoc a b -> a -> b
-assocMaybe :: (Eq a) => Assoc a b -> a -> Maybe b
-assocDefaultUsing :: (a -> a -> Bool) -> b -> Assoc a b -> a -> b
-mapAssoc :: (b -> c) -> Assoc a b -> Assoc a c
-extendAssoc_C :: (Eq a) => (b -> b -> b) -> Assoc a b -> (a,b) -> Assoc a b
-plusAssoc_C :: (Eq a) => (b -> b -> b) -> Assoc a b -> Assoc a b -> Assoc a b
- -- combining fn takes (old->new->result)
-
-emptyAssoc = []
-unitAssoc a b = [(a,b)]
-assocElts xs = xs
-
-assocDefaultUsing eq deflt ((k,v) : rest) key
- | k `eq` key = v
- | otherwise = assocDefaultUsing eq deflt rest key
-
-assocDefaultUsing eq deflt [] key = deflt
-
-assoc crash_msg list key = assocDefaultUsing (==) (panic ("Failed in assoc: " ++ crash_msg)) list key
-assocDefault deflt list key = assocDefaultUsing (==) deflt list key
-assocUsing eq crash_msg list key = assocDefaultUsing eq (panic ("Failed in assoc: " ++ crash_msg)) list key
-
-assocMaybe alist key
- = lookup alist
- where
- lookup [] = Nothing
- lookup ((tv,ty):rest) = if key == tv then Just ty else lookup rest
-
-mapAssoc f alist = [(key, f val) | (key,val) <- alist]
-
-plusAssoc_C combine [] new = new -- Shortcut for common case
-plusAssoc_C combine old new = foldl (extendAssoc_C combine) old new
-
-extendAssoc_C combine old_list (new_key, new_val)
- = go old_list
- where
- go [] = [(new_key, new_val)]
- go ((old_key, old_val) : old_list)
- | new_key == old_key = ((old_key, old_val `combine` new_val) : old_list)
- | otherwise = (old_key, old_val) : go old_list
-\end{code}
-
-
-@mkLookupFun eq alist@ is a function which looks up
-its argument in the association list @alist@, returning a Maybe type.
-@mkLookupFunDef@ is similar except that it is given a value to return
-on failure.
-
-\begin{code}
-mkLookupFun :: (key -> key -> Bool) -- Equality predicate
- -> [(key,val)] -- The assoc list
- -> key -- The key
- -> Maybe val -- The corresponding value
-
-mkLookupFun eq alist s
- = case [a | (s',a) <- alist, s' `eq` s] of
- [] -> Nothing
- (a:_) -> Just a
-
-findInList :: (a -> Bool) -> [a] -> Maybe a
-findInList p [] = Nothing
-findInList p (x:xs) | p x = Just x
- | otherwise = findInList p xs
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[Utils-dups]{Duplicate-handling}
-%* *
-%************************************************************************
-
-\begin{code}
-hasNoDups :: (Eq a) => [a] -> Bool
-
-hasNoDups xs = f [] xs
- where
- f seen_so_far [] = True
- f seen_so_far (x:xs) = if x `is_elem` seen_so_far then
- False
- else
- f (x:seen_so_far) xs
-
- is_elem = isIn "hasNoDups"
-\end{code}
-
-\begin{code}
-equivClasses :: (a -> a -> Ordering) -- Comparison
- -> [a]
- -> [[a]]
-
-equivClasses cmp stuff@[] = []
-equivClasses cmp stuff@[item] = [stuff]
-equivClasses cmp items
- = runs eq (sortLe le items)
- where
- eq a b = case cmp a b of { EQ -> True; _ -> False }
- le a b = case cmp a b of { LT -> True; EQ -> True; GT -> False }
-\end{code}
-
-The first cases in @equivClasses@ above are just to cut to the point
-more quickly...
-
-@runs@ groups a list into a list of lists, each sublist being a run of
-identical elements of the input list. It is passed a predicate @p@ which
-tells when two elements are equal.
-
-\begin{code}
-runs :: (a -> a -> Bool) -- Equality
- -> [a]
- -> [[a]]
-
-runs p [] = []
-runs p (x:xs) = case (span (p x) xs) of
- (first, rest) -> (x:first) : (runs p rest)
-\end{code}
-
-\begin{code}
-removeDups :: (a -> a -> Ordering) -- Comparison function
- -> [a]
- -> ([a], -- List with no duplicates
- [[a]]) -- List of duplicate groups. One representative from
- -- each group appears in the first result
-
-removeDups cmp [] = ([], [])
-removeDups cmp [x] = ([x],[])
-removeDups cmp xs
- = case (mapAccumR collect_dups [] (equivClasses cmp xs)) of { (dups, xs') ->
- (xs', dups) }
- where
- collect_dups dups_so_far [x] = (dups_so_far, x)
- collect_dups dups_so_far dups@(x:xs) = (dups:dups_so_far, x)
-
-findDupsEq :: (a->a->Bool) -> [a] -> [[a]]
-findDupsEq eq [] = []
-findDupsEq eq (x:xs) | null eq_xs = findDupsEq eq xs
- | otherwise = (x:eq_xs) : findDupsEq eq neq_xs
- where
- (eq_xs, neq_xs) = partition (eq x) xs
-\end{code}
-
-
-\begin{code}
-equivClassesByUniq :: (a -> Unique) -> [a] -> [[a]]
- -- NB: it's *very* important that if we have the input list [a,b,c],
- -- where a,b,c all have the same unique, then we get back the list
- -- [a,b,c]
- -- not
- -- [c,b,a]
- -- Hence the use of foldr, plus the reversed-args tack_on below
-equivClassesByUniq get_uniq xs
- = eltsUFM (foldr add emptyUFM xs)
- where
- add a ufm = addToUFM_C tack_on ufm (get_uniq a) [a]
- tack_on old new = new++old
-\end{code}
-
-
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