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|
-----------------------------------------------------------------------------
-- Pattern completeness analysis for Curry programs
--
-- This analysis checks for each function in a Curry program whether
-- this function is completely defined, i.e., reducible on all ground
-- constructor terms
--
-- Johannes Koj, October 2000
-- Michael Hanus, June 2006
-----------------------------------------------------------------------------
module PatternComplete(CompletenessType(..),
analyseCompleteness,
analyseTotallyDefined) where
import FlatCurry.Types
import Dependency(analyseWithDependencies)
------------------------------------------------------------------------------
-- The completeness analysis must be applied to complete programs,
-- i.e., modules together with all their imported modules (although
-- functions are locally checked, the definition of all data types
-- used in the patterns are needed).
-- It assigns to a FlatCurry program the list of all qualified function names
-- together with a flag indicating whether this function is completely
-- defined on its input types (i.e., reducible for all ground data terms).
-- The possible outcomes of the completeness analysis:
data CompletenessType =
Complete -- completely defined
| InComplete -- incompletely defined
| InCompleteOr -- incompletely defined in each branch of an "Or"
analyseTotallyDefined :: [TypeDecl] -> [FuncDecl] -> [(QName,CompletenessType)]
analyseTotallyDefined types = analyseWithDependencies (analyseCompleteness types) cAnd
where cAnd = foldr combineAndResults Complete
analyseCompleteness :: [TypeDecl] -> FuncDecl -> CompletenessType
analyseCompleteness types fdecl = anaFun fdecl
where
anaFun (Func _ _ _ _ (Rule _ e)) = isComplete types e
anaFun (Func _ _ _ _ (External _)) = Complete
isComplete :: [TypeDecl] -> Expr -> CompletenessType
isComplete _ (Var _) = Complete
isComplete _ (Lit _) = Complete
isComplete types (Comb _ f es) =
if f==("Prelude","commit") && length es == 1
then isComplete types (head es)
else Complete
isComplete _ (Free _ _) = Complete
isComplete _ (Let _ _) = Complete
isComplete types (Or e1 e2) =
combineOrResults (isComplete types e1) (isComplete types e2)
-- if there is no branch, it is incomplete:
isComplete _ (Case _ _ []) = InComplete
-- for literal branches we usually assume that not all alternatives are provided:
isComplete _ (Case _ _ (Branch (LPattern _) _ : _)) = InComplete
isComplete types (Case _ _ (Branch (Pattern cons pvs) bexp : ces)) =
checkAllCons (getConstructors cons types) (Branch (Pattern cons pvs) bexp : ces)
where
-- check for occurrences of all constructors in each case branch:
checkAllCons [] _ = Complete
checkAllCons (_:_) [] = InComplete
checkAllCons (_:_) (Branch (LPattern _) _ : _) = InComplete -- should not occur
checkAllCons (c:cs) (Branch (Pattern i _) e : ps) =
combineAndResults (checkAllCons (removeConstructor i (c:cs)) ps)
(isComplete types e)
isComplete types (Typed e _) = isComplete types e
-- Combines the completeness results in different Or branches.
combineOrResults :: CompletenessType -> CompletenessType -> CompletenessType
combineOrResults Complete _ = Complete
combineOrResults InComplete Complete = Complete
combineOrResults InComplete InComplete = InCompleteOr
combineOrResults InComplete InCompleteOr = InCompleteOr
combineOrResults InCompleteOr Complete = Complete
combineOrResults InCompleteOr InComplete = InCompleteOr
combineOrResults InCompleteOr InCompleteOr = InCompleteOr
-- Combines the completeness results in different case branches.
combineAndResults :: CompletenessType -> CompletenessType -> CompletenessType
combineAndResults InComplete _ = InComplete
combineAndResults Complete Complete = Complete
combineAndResults Complete InComplete = InComplete
combineAndResults Complete InCompleteOr = InCompleteOr
combineAndResults InCompleteOr Complete = InCompleteOr
combineAndResults InCompleteOr InComplete = InComplete
combineAndResults InCompleteOr InCompleteOr = InCompleteOr
-- get the list of all constructors of the same datatype for a given constructor:
getConstructors :: QName -> [TypeDecl] -> [ConsDecl]
getConstructors _ [] = error "Internal compiler error: case datatype not found!"
getConstructors cons (TypeSyn _ _ _ _ : types) = getConstructors cons types
getConstructors cons (Type _ _ _ cdecls : types) =
if hasCons cdecls then cdecls
else getConstructors cons types
where
hasCons [] = False
hasCons (Cons cs _ _ _ : cstrs) = cons==cs || hasCons cstrs
-- remove a constructor from a list of constructors
removeConstructor :: QName -> [ConsDecl] -> [ConsDecl]
removeConstructor c1 [] = error ("Constructor "++show c1++" not found!!")
removeConstructor c1 ((Cons c2 a vis ts):cs)
| c1==c2 = cs
| otherwise = (Cons c2 a vis ts):(removeConstructor c1 cs)
|
