org.jpl7

Class Variable

java.lang.Object

org.jpl7.Term

org.jpl7.Variable

public class Variable
extends Term

This class supports Java representations of Prolog variables.

A jpl.Variable instance is equivalent to a variable in a fragment of Prolog source text: it is *not* a "live" variable within a Prolog stack or heap. A corresponding Prolog variable is created only upon opening a Query whose goal refers to a Variable (and then only temporarily).

Copyright (C) 2004 Paul Singleton

Copyright (C) 1998 Fred Dushin

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	index
java.lang.String	name the name of this Variable (may be changed as of April 2020)
protected term_t	term_ defined between Query.open() and Query.get2()

Constructor Summary

Constructors

Constructor and Description
Variable() Create a new don't tell Variable with new sequential name of the form "_261".
Variable(java.lang.String name) Create a new Variable with 'name' (which must not be null or ""), and may one day be constrained to comply with traditional Prolog syntax.

Method Summary

Modifier and Type	Method and Description
Term[]	args() The arguments of this Term.
int	arity() returns, as an int, the arity of a Term
boolean	equals(java.lang.Object o) A Variable is equal to another if their names are the same Totally lexical textual interpretation of vars, not related to bindings Anonymous var _ is always different (including to itsef)
protected void	getSubst(java.util.Map<java.lang.String,Term> varnames_to_Terms, java.util.Map<term_t,Variable> vars_to_Vars) This can be used to get the **current** solution binding of the Variable instance.
boolean	hasFunctor(java.math.BigInteger value, int arity) Tests whether this Term's functor has 'name' and 'arity'
boolean	hasFunctor(double value, int arity) Tests whether this Term's functor has 'name' and 'arity'
boolean	hasFunctor(long value, int arity) Tests whether this Term's functor has 'name' and 'arity'
boolean	hasFunctor(java.lang.String name, int arity) Whether this Term's functor has 'name' and 'arity' (c.f.
int	hashCode()
java.lang.String	name() the lexical name of this Variable
protected void	put(java.util.Map<java.lang.String,term_t> varnames_to_vars, term_t term) To put a Variable, we must check whether a (non-anonymous) variable with the same name has already been put in the Term.
void	setName(java.lang.String name)
java.lang.String	toString() Returns a Prolog source text representation of this Variable
int	type() returns the type of this subclass of Term, i.e.
java.lang.String	typeName() returns the typeName of this subclass of Term, i.e.

Methods inherited from class org.jpl7.Term

arg, atomListToStringArray, atomType, bigValue, doubleValue, floatValue, getSubsts, getTerm, getTerm, intArrayArrayToList, intArrayToList, intValue, isAtom, isAtomOfNameType, isBig, isBigInteger, isCompound, isFloat, isInteger, isJFalse, isJNull, isJRef, isJTrue, isJVoid, isList, isList, isListNil, isListPair, isVariable, jrefToObject, listLength, listLength, listToTermArray, listToTermArray, longValue, object, objectToJRef, put, putParams, putParams, putParams1, putParams2, putTerm, putTerms, ref, stringArrayToList, termArrayToList, textParamsToTerm, textToTerm, toString, toTermArray

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

index

protected transient int index

name

public java.lang.String name

the name of this Variable (may be changed as of April 2020)

term_

protected transient term_t term_

defined between Query.open() and Query.get2()

Constructor Detail

Variable

public Variable()

Create a new don't tell Variable with new sequential name of the form "_261".

Variable

public Variable(java.lang.String name)

Create a new Variable with 'name' (which must not be null or ""), and may one day be constrained to comply with traditional Prolog syntax.

Parameters:

name - the source name of this Variable

Method Detail

args

public final Term[] args()

Description copied from class: Term

The arguments of this Term.

Note that a SWI Prolog 7.x compound term can have zero arguments.

This method returns an empty Term[] from an Atom, Float, Integer or JRef, approximating the behaviour of SWI Prolog's =../2

Overrides:

args in class Term

Returns:

the arguments of a Compound

arity

public int arity()

returns, as an int, the arity of a Term

Overrides:

arity in class Term

Returns:

the arity of a Term

equals

public boolean equals(java.lang.Object o)

A Variable is equal to another if their names are the same Totally lexical textual interpretation of vars, not related to bindings Anonymous var _ is always different (including to itsef)

Overrides:

equals in class java.lang.Object

Parameters:

o - The Object to compare.

Returns:

true if the Object is a Variable and the above condition apply.

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

getSubst

protected final void getSubst(java.util.Map<java.lang.String,Term> varnames_to_Terms,
                              java.util.Map<term_t,Variable> vars_to_Vars)

This can be used to get the **current** solution binding of the Variable instance. So we are calling when the goal is in a solution This method returns nothing but modifies the argument mappings, by filling them with the current solution binding of the Variable instance. If Variable instance is anonymous or a dont-tell-me variable, then do nothing Otherwise, if the Variable instance is not already in the varnames_to_Terms Map, put the result of converting the term_t to which this variable has been unified (in the current solution) to a Term in the Map, keyed on this Variable's name. In binding the Variable instance to the Term (in the current solution), such Term may also refer to free variables, whose maps are stores in vars_to_Vars

Overrides:

getSubst in class Term

Parameters:

varnames_to_Terms - A Map of bindings from variable names to JPL Terms.

vars_to_Vars - A Map from Prolog variables to JPL Variables.

hasFunctor

public boolean hasFunctor(java.math.BigInteger value,
                          int arity)

Description copied from class: Term

Tests whether this Term's functor has 'name' and 'arity'

For Float and Integer, mimics behaviour of SWI Prolog's functor/3

Overrides:

hasFunctor in class Term

Parameters:

value - a possible name for the functor of a term

arity - an arity 0+

Returns:

whether this Term's functor has 'name' and 'arity'

hasFunctor

public boolean hasFunctor(java.lang.String name,
                          int arity)

Description copied from class: Term

Whether this Term's functor has 'name' and 'arity' (c.f. behaviour of SWI Prolog's functor/3)

Overrides:

hasFunctor in class Term

Parameters:

name - a possible name for the functor of a term

arity - an arity 0+

Returns:

whether this Term's functor has 'name' and 'arity'

hasFunctor

public boolean hasFunctor(long value,
                          int arity)

Description copied from class: Term

Tests whether this Term's functor has 'name' and 'arity'

For Float and Integer, mimics behaviour of SWI Prolog's functor/3

Overrides:

hasFunctor in class Term

Parameters:

value - a possible name for the functor of a term

arity - an arity 0+

Returns:

whether this Term's functor has 'name' and 'arity'

hasFunctor

public boolean hasFunctor(double value,
                          int arity)

Description copied from class: Term

Tests whether this Term's functor has 'name' and 'arity'

For Float and Integer, mimics behaviour of SWI Prolog's functor/3

Overrides:

hasFunctor in class Term

Parameters:

value - a possible name for the functor of a term

arity - an arity 0+

Returns:

whether this Term's functor has 'name' and 'arity'

name

public final java.lang.String name()

the lexical name of this Variable

Overrides:

name in class Term

Returns:

the lexical name of this Variable

setName

public void setName(java.lang.String name)

Overrides:

setName in class Term

put

protected final void put(java.util.Map<java.lang.String,term_t> varnames_to_vars,
                         term_t term)

To put a Variable, we must check whether a (non-anonymous) variable with the same name has already been put in the Term. If one has, then the corresponding Prolog variable has been stashed in the varnames_to_vars Map, keyed by the Variable name, so we can look it up and reuse it (this way, the sharing of variables in the Prolog term reflects the sharing of Variable names in the Term. Otherwise, if this Variable name has not already been seen in the Term, then we put a new Prolog variable and add it into the Map (keyed by this Variable name).

Specified by:

put in class Term

Parameters:

varnames_to_vars - A Map from variable names to Prolog variables.

term - A (previously created) term_t which is to be set to a (new or reused) Prolog variable.

toString

public java.lang.String toString()

Returns a Prolog source text representation of this Variable

Overrides:

toString in class java.lang.Object

Returns:

a Prolog source text representation of this Variable

type

public final int type()

returns the type of this subclass of Term, i.e. Prolog.VARIABLE

Specified by:

type in class Term

Returns:

the type of this subclass of Term, i.e. Prolog.VARIABLE

typeName

public java.lang.String typeName()

returns the typeName of this subclass of Term, i.e. "Variable"

Specified by:

typeName in class Term

Returns:

the typeName of this subclass of Term, i.e. "Variable"