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sourcecode:
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module Language.Prolog.Goodies
( plList, isPlVar, rootOf, argsOf, goalVars, termVars, termsVars
, termVarOccs, goalConstrs, termConstrs )
where
import Data.List ( union )
import Language.Prolog.Types
----------------------------------------------------------------------------
--- Constructs a Prolog list object from a list of Prolog terms.
plList :: [PlTerm] -> PlTerm
plList = foldr (\t ts -> PlStruct "." [t,ts]) (PlAtom "[]")
----------------------------------------------------------------------------
-- Selector operations for Prolog programs.
--- Is a Prolog term a variable?
isPlVar :: PlTerm -> Bool
isPlVar pterm = case pterm of PlVar _ -> True
_ -> False
--- The name and the arity of the root of a Prolog term,
--- where the names of variables are ignored (i.e., empty).
rootOf :: PlTerm -> (String,Int)
rootOf pterm = case pterm of
PlVar _ -> ("", 0)
PlInt i -> (show i, 0)
PlFloat x -> (show x, 0)
PlAtom a -> (a, 0)
PlStruct s args -> (s, length args)
--- The arguments of a Prolog term.
argsOf :: PlTerm -> [PlTerm]
argsOf pterm = case pterm of
PlStruct _ args -> args
_ -> []
--- The set of all variables occurring in a Prolog goal.
goalVars :: PlGoal -> [String]
goalVars pgoal = case pgoal of
PlLit _ ts -> termsVars ts
PlNeg goals -> unionMap goalVars goals
PlCond gs1 gs2 gs3 -> unionMap (unionMap goalVars) [gs1,gs2,gs3]
--- The set of all variables occurring in a Prolog term.
termVars :: PlTerm -> [String]
termVars pterm = case pterm of
PlVar v -> [v]
PlStruct _ ts -> termsVars ts
_ -> []
--- The set of all variables occurring in a list of Prolog terms.
termsVars :: [PlTerm] -> [String]
termsVars = unionMap termVars
--- The multi-set of all occurrences of variables in a Prolog term.
termVarOccs :: PlTerm -> [String]
termVarOccs pterm = case pterm of
PlVar v -> [v]
PlStruct _ ts -> concatMap termVars ts
_ -> []
--- The set of all data constructors together with their arities
--- used in a Prolog goal.
goalConstrs :: PlGoal -> [(String,Int)]
goalConstrs pgoal = case pgoal of
PlLit _ ts -> unionMap termConstrs ts
PlNeg goals -> unionMap goalConstrs goals
PlCond gs1 gs2 gs3 -> unionMap (unionMap goalConstrs) [gs1,gs2,gs3]
--- The set of all data constructors together with their arities
--- used in a Prolog term.
termConstrs :: PlTerm -> [(String,Int)]
termConstrs pterm = case pterm of
PlAtom a -> [(a,0)]
PlStruct s ts -> union [(s, length ts)] (unionMap termConstrs ts)
_ -> []
----------------------------------------------------------------------------
-- Auxiliaries:
unionMap :: Eq b => (a -> [b]) -> [a] -> [b]
unionMap f = foldr union [] . map f
----------------------------------------------------------------------------
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