eu.bandm.tools.paisley

Class Variable<A>

java.lang.Object

eu.bandm.tools.paisley.Pattern<A>

eu.bandm.tools.paisley.Variable<A>

All Implemented Interfaces:

Extractor<A>, Serializable, Cloneable

public final class Variable<A>
extends Pattern<A>
implements Extractor<A>

Class of pattern variables.

A pattern variable is deterministic, matches any object and binds itself.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
Variable() Creates a new anonymous variable.
Variable(String name) Creates a new named variable.

Method Summary

Modifier and Type	Method and Description
boolean	binds(Variable<?> var) Checks whether a variable is bound by this pattern.
void	clear(boolean recursively) Disposes of all internal state related to results and nondeterminism.
Variable<A>	clone() Makes a matching-state copy if this pattern.
protected void	compileCut(eu.bandm.tools.paisley.CompilationContext context)
protected void	compileCut(eu.bandm.tools.paisley.CompilationContext context, boolean recursively)
protected void	compileMatchAgain(eu.bandm.tools.paisley.CompilationContext context)
String	getName() Returns the name of this variable.
A	getValue() Returns the current value bound to this variable.
<B> Motif<A,B>	lambda(Pattern<B> body)
boolean	match(A target) Attempts to match this pattern against a given object.
Pattern<A>	plus(Pattern<? super A> root) Returns the "plus" variant of the Kleene fixpoint of a pattern as a function of this variable.
boolean	preserves(Variable<?> var) Checks whether a variable is preserved by this pattern, unconditionally.
boolean	preserves(Variable<?> var, boolean success) Checks whether a variable is preserved by this pattern, conditionally on success or failure.
Pattern<A>	star(Pattern<? super A> root) Returns the "star" variant of the Kleene fixpoint of a pattern as a function of this variable.
String	toString()

Methods inherited from class eu.bandm.tools.paisley.Pattern

all, all, all, all, all, and, andThen, andThen, any, any, aside, both, clear, compareTo, compile, compileClear, compileClear, compileIsDeterministic, compileMatch, compileSubPattern, compileThis, compileUpTo, cut, cut, DEBUG, either, enPassant, eq, eqNull, equal, filter, flatten, forInstancesOf, isDeterministic, limit, main, matchAgain, matchOnce, matchVar, narrow, neq, neqNull, newAll, noMatch, none, or, orElse, orElse, repeat, some, some, some, some, someMatch, startCompile, test, transform, uniquely, variable, variable

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface eu.bandm.tools.paisley.Extractor

bind, eagerBindings, lazyBindings

Constructor Detail

Variable

public Variable()

Creates a new anonymous variable.

Variable

public Variable(String name)

Creates a new named variable. Variable names are for user-level annotation purposes only, they have no effect on matching behaviour.

Parameters:

name - the variable name.

Method Detail

getName

public String getName()

Returns the name of this variable.

Returns:

the name of this variable, or null if this variable is anonymous.

getValue

public A getValue()

Returns the current value bound to this variable. The value is initially null. It is set to a meaningful value by a successful match with a pattern that guarantees to bind the variable. It may be set to an unspecified value by a match with a pattern that does not guarantee to preserve the variable.

Specified by:

getValue in interface Extractor<A>

Returns:

the current value bound to this variable.

See Also:

Pattern.binds(eu.bandm.tools.paisley.Variable<?>), Pattern.preserves(eu.bandm.tools.paisley.Variable<?>, boolean)

clear

public void clear(boolean recursively)

Disposes of all internal state related to results and nondeterminism.

The default implementation does nothing. This implementation resets the variable value to null.

Overrides:

clear in class Pattern<A>

Parameters:

recursively - true if all subpatterns should be deactivated, false otherwise.

match

public boolean match(A target)

Attempts to match this pattern against a given object. If the class of this pattern imposes a specific order on matches, the first one is chosen. This implementation sets the variable value to target.

Specified by:

match in class Pattern<A>

Parameters:

target - the object to match against

Returns:

true

See Also:

Pattern.binds(Variable), Pattern.preserves(Variable, boolean)

binds

public boolean binds(Variable<?> var)

Description copied from class: Pattern

Checks whether a variable is bound by this pattern.

The default implementation returns false.

Overrides:

binds in class Pattern<A>

Parameters:

var - a pattern variable

Returns:

true if this variable equals the given variable, false otherwise.

preserves

public boolean preserves(Variable<?> var,
                         boolean success)

Description copied from class: Pattern

Checks whether a variable is preserved by this pattern, conditionally on success or failure.

The default implementation returns false.

Overrides:

preserves in class Pattern<A>

Parameters:

var - a pattern variable

success - specifies preservation on success or failure

Returns:

true if success is false or this variable equals the given variable, false otherwise.

preserves

public boolean preserves(Variable<?> var)

Description copied from class: Pattern

Checks whether a variable is preserved by this pattern, unconditionally.

The default implementation returns false.

Overrides:

preserves in class Pattern<A>

Parameters:

var - a pattern variable

Returns:

true if the variable value is guaranteed to be unaffected by any matching attempt with this pattern.

toString

public String toString()

Overrides:

toString in class Object

clone

public Variable<A> clone()

Description copied from class: Pattern

Makes a matching-state copy if this pattern.

Subclasses must override this method if necessary to honour the following rules for all transitively reachable patterns:

• Subpatterns that are instances of Variable must be shared. This implies that clone() must return this.
• Fields that do not refer to subpatterns, but to matching state (changed by invocations of Pattern.match(A), Pattern.matchAgain(), Pattern.cut() or Pattern.clear()) must be duplicated. If matching state changes are effected by modification of other objects, these must be duplicated. In summary, matching operations on this pattern and its copy must not interfere, with the exception of variable bindings.
• Fields neither referring to subpatterns nor to matching state may be either shared or duplicated. The usage of such fields in a modifiable way (such that the distinction is relevant) is strongly deprecated.
• Patterns whose fields need not be duplicated need not be duplicated themselves, but may return this.

Overrides:

clone in class Pattern<A>

lambda

public <B> Motif<A,B> lambda(Pattern<B> body)

plus

public Pattern<A> plus(Pattern<? super A> root)

Returns the "plus" variant of the Kleene fixpoint of a pattern as a function of this variable.

Conceptually, x.star(p) is equivalent to the pattern arising from p.clone() by substituting x.star(p) for x. Note that this cannot be used naively for implementation, since the ensuing recursive substitution would not terminate. The actual implementation guarantees to produce only as many new subpatterns as dynamically necessary.

See Also:

star(Pattern), Pattern.clone(), Extractor.bind(Pattern, Pattern)

star

public Pattern<A> star(Pattern<? super A> root)

Returns the "star" variant of the Kleene fixpoint of a pattern as a function of this variable.

Conceptually, x.star(p) is equivalent to either(x, x.plus(p)).

See Also:

Pattern.either(Pattern, Pattern), plus(Pattern)

compileMatchAgain

protected void compileMatchAgain(eu.bandm.tools.paisley.CompilationContext context)

Overrides:

compileMatchAgain in class Pattern<A>

compileCut

protected void compileCut(eu.bandm.tools.paisley.CompilationContext context)

Overrides:

compileCut in class Pattern<A>

compileCut

protected void compileCut(eu.bandm.tools.paisley.CompilationContext context,
                          boolean recursively)

Overrides:

compileCut in class Pattern<A>