Module Rewriting.Rules

Library for representation of rules and term rewriting systems.

Author: Jan-Hendrik Matthes

Version: November 2016

Summary of exported operations:

showRule :: (a -> String) -> (Term a,Term a) -> String  Deterministic 
Transforms a rule into a string representation.
showTRS :: (a -> String) -> [(Term a,Term a)] -> String  Deterministic 
Transforms a term rewriting system into a string representation.
rRoot :: (Term a,Term a) -> Either Int a  Deterministic 
Returns the root symbol (variable or constructor) of a rule.
rCons :: Eq a => (Term a,Term a) -> [a]  Deterministic 
Returns a list without duplicates of all constructors in a rule.
rVars :: (Term a,Term a) -> [Int]  Deterministic 
Returns a list without duplicates of all variables in a rule.
maxVarInRule :: (Term a,Term a) -> Maybe Int  Deterministic 
Returns the maximum variable in a rule or Nothing if no variable exists.
minVarInRule :: (Term a,Term a) -> Maybe Int  Deterministic 
Returns the minimum variable in a rule or Nothing if no variable exists.
maxVarInTRS :: [(Term a,Term a)] -> Maybe Int  Deterministic 
Returns the maximum variable in a term rewriting system or Nothing if no variable exists.
minVarInTRS :: [(Term a,Term a)] -> Maybe Int  Deterministic 
Returns the minimum variable in a term rewriting system or Nothing if no variable exists.
renameRuleVars :: Int -> (Term a,Term a) -> (Term a,Term a)  Deterministic 
Renames the variables in a rule by the given number.
renameTRSVars :: Int -> [(Term a,Term a)] -> [(Term a,Term a)]  Deterministic 
Renames the variables in every rule of a term rewriting system by the given number.
normalizeRule :: (Term a,Term a) -> (Term a,Term a)  Deterministic 
Normalizes a rule by renaming all variables with an increasing order, starting from the minimum possible variable.
normalizeTRS :: [(Term a,Term a)] -> [(Term a,Term a)]  Deterministic 
Normalizes all rules in a term rewriting system by renaming all variables with an increasing order, starting from the minimum possible variable.
isVariantOf :: Eq a => (Term a,Term a) -> (Term a,Term a) -> Bool  Deterministic 
Checks whether the first rule is a variant of the second rule.
isLeftLinear :: [(Term a,Term a)] -> Bool  Deterministic 
Checks whether a term rewriting system is left-linear.
isLeftNormal :: [(Term a,Term a)] -> Bool  Deterministic 
Checks whether a term rewriting system is left-normal.
isRedex :: Eq a => [(Term a,Term a)] -> Term a -> Bool  Deterministic 
Checks whether a term is reducible with some rule of the given term rewriting system.
isPattern :: Eq a => [(Term a,Term a)] -> Term a -> Bool  Deterministic 
Checks whether a term is a pattern, i.e., an root-reducible term where the argaccording to the given term rewriting system.
isConsBased :: Eq a => [(Term a,Term a)] -> Bool  Deterministic 
Checks whether a term rewriting system is constructor-based.
isDemandedAt :: Int -> (Term a,Term a) -> Bool  Deterministic 
Checks whether the given argument position of a rule is demanded.

Exported datatypes:


Rule

A rule represented as a pair of terms and parameterized over the kind of function symbols, e.g., strings.

Type synonym: Rule a = (Term a,Term a)


TRS

A term rewriting system represented as a list of rules and parameterized over the kind of function symbols, e.g., strings.

Type synonym: TRS a = [Rule a]


Exported operations:

showRule :: (a -> String) -> (Term a,Term a) -> String  Deterministic 

Transforms a rule into a string representation.

showTRS :: (a -> String) -> [(Term a,Term a)] -> String  Deterministic 

Transforms a term rewriting system into a string representation.

rRoot :: (Term a,Term a) -> Either Int a  Deterministic 

Returns the root symbol (variable or constructor) of a rule.

Further infos:
  • solution complete, i.e., able to compute all solutions

rCons :: Eq a => (Term a,Term a) -> [a]  Deterministic 

Returns a list without duplicates of all constructors in a rule.

rVars :: (Term a,Term a) -> [Int]  Deterministic 

Returns a list without duplicates of all variables in a rule.

maxVarInRule :: (Term a,Term a) -> Maybe Int  Deterministic 

Returns the maximum variable in a rule or Nothing if no variable exists.

minVarInRule :: (Term a,Term a) -> Maybe Int  Deterministic 

Returns the minimum variable in a rule or Nothing if no variable exists.

maxVarInTRS :: [(Term a,Term a)] -> Maybe Int  Deterministic 

Returns the maximum variable in a term rewriting system or Nothing if no variable exists.

minVarInTRS :: [(Term a,Term a)] -> Maybe Int  Deterministic 

Returns the minimum variable in a term rewriting system or Nothing if no variable exists.

renameRuleVars :: Int -> (Term a,Term a) -> (Term a,Term a)  Deterministic 

Renames the variables in a rule by the given number.

renameTRSVars :: Int -> [(Term a,Term a)] -> [(Term a,Term a)]  Deterministic 

Renames the variables in every rule of a term rewriting system by the given number.

normalizeRule :: (Term a,Term a) -> (Term a,Term a)  Deterministic 

Normalizes a rule by renaming all variables with an increasing order, starting from the minimum possible variable.

normalizeTRS :: [(Term a,Term a)] -> [(Term a,Term a)]  Deterministic 

Normalizes all rules in a term rewriting system by renaming all variables with an increasing order, starting from the minimum possible variable.

isVariantOf :: Eq a => (Term a,Term a) -> (Term a,Term a) -> Bool  Deterministic 

Checks whether the first rule is a variant of the second rule.

isLeftLinear :: [(Term a,Term a)] -> Bool  Deterministic 

Checks whether a term rewriting system is left-linear.

isLeftNormal :: [(Term a,Term a)] -> Bool  Deterministic 

Checks whether a term rewriting system is left-normal.

isRedex :: Eq a => [(Term a,Term a)] -> Term a -> Bool  Deterministic 

Checks whether a term is reducible with some rule of the given term rewriting system.

isPattern :: Eq a => [(Term a,Term a)] -> Term a -> Bool  Deterministic 

Checks whether a term is a pattern, i.e., an root-reducible term where the argaccording to the given term rewriting system.

isConsBased :: Eq a => [(Term a,Term a)] -> Bool  Deterministic 

Checks whether a term rewriting system is constructor-based.

isDemandedAt :: Int -> (Term a,Term a) -> Bool  Deterministic 

Checks whether the given argument position of a rule is demanded. Returns True if the corresponding argument term is a constructor term.