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| Description |
Routines to transform SimpleRules and productions into
Chomsky Normal Form.
SimpleRules such as
f(g(g(X)),X) => c(X) .
are transformed into equivalent FullRules having Term patters of
maximum depth 1 and Variables occurring at most once. For instance, the
Chomsky Normal Form of the above SimpleRule is
| L : f(!2, X!1), !2 : g(!3), !3 : g(X!0), @!Inters : cons(X!0, X!1) => L : c(X!0) .
Similarly, productions such as
@a : f(g(@b)) .
are transformed into
@a : f(%0) .
%0 : g(@b) .
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| Synopsis |
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| Basic Operations |
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| data RSt |
| State for the normalization of SimpleRules. | | Constructors | | RSt | | | counterR :: !Int | Used to generate fresh variables. | | aliases :: !(Map Variable [Variable]) | Stores all the aliases for a variable. |
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| type CNFRSt = State RSt |
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| data GSt |
| State for the normalization of productions. | | Constructors | | GSt | | | counterG :: !Int | Used to generate fresh Labels. | | cnfProductions :: ![(Label, [Term])] | Productions in CNF |
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| type CNFGSt = State GSt |
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| newId :: CNFRSt Int |
| Generate a fresh Int and increment counterR. |
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| newVariable :: CNFRSt Variable |
| Generate a fresh for-internal-use-only Variable. |
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| newLabel :: CNFGSt Label |
| Generate fresh Label. |
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| writeProduction :: (Label, [Term]) -> CNFGSt () |
| Add extra productions to GSt. |
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| newAlias :: Variable -> CNFRSt Variable |
| Generte a fresh alias for a Variable, and store the alias in the
aliases map. |
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| Clause Normalization |
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| aliasesIntersections :: CNFRSt [Clause] |
| Generate a list of intersection Clauses for each distinct pair of
aliases for a Variable. |
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| flattenClause :: Clause -> CNFRSt [Clause] |
| Transform a Clause having an arbitrary Term as pattern into
a list of Clauses where pattern have maximum depth 1. |
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| normalizeClause :: Clause -> CNFRSt [Clause] |
| Transform a Clause having an arbitrary Term as pattern into
a Clause list having only patterns with maximum depth 1, and each
Variable occurring at most once in each Clause. |
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| aliasSubst :: CNFRSt Subst |
| The Subst associating a Variable with its first alias. |
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| Main Routines |
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| normalizeSimpleRule :: Rule -> Rule |
| Transform a SimpleRule into a FullRule. |
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| normalizeSimpleRules :: [Rule] -> [Rule] |
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| flattenProduction :: (Label, [Term]) -> CNFGSt () |
| Flatten a production. |
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| normalizeProductions :: [(Label, [Term])] -> [(Label, [Term])] |
| Normalize productions. |
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| Produced by Haddock version 0.6 |
