org.apache.jena.sparql.expr

Class ExprFunction

java.lang.Object

org.apache.jena.sparql.expr.ExprNode

org.apache.jena.sparql.expr.ExprFunction

All Implemented Interfaces:

Expr

Direct Known Subclasses:

ExprFunction0, ExprFunction1, ExprFunction2, ExprFunction3, ExprFunctionN, ExprFunctionOp

public abstract class ExprFunction
extends ExprNode

A function in the expression hierarchy. Everything that is evaluable (i.e. not NodeValue, NodeVar) is a function). It is useful to distinguish between values, vars and functions. The exists operations (which take a op, not arguments) are functions of zero arguments.

Field Summary

Fields inherited from interface org.apache.jena.sparql.expr.Expr

CMP_EQUAL, CMP_GREATER, CMP_INDETERMINATE, CMP_LESS, CMP_UNEQUAL, NONE

Method Summary

Modifier and Type	Method and Description
boolean	equals(Expr other, boolean bySyntax) General equality operation - consider this to be 'protected'
abstract Expr	getArg(int i)
List<Expr>	getArgs()
ExprFunction	getFunction() Get the function (returns null if not a function)
String	getFunctionIRI() URI for this function, whether custom or specification defined URI (these are keywords in the language)
String	getFunctionName(SerializationContext cxt) Name used in a functional form (i.e.
String	getFunctionPrintName(SerializationContext cxt) Name used for output in SPARQL format needing functional form (no specific keyword).
FunctionLabel	getFunctionSymbol() Used to get a unique name for the function, which is intern'ed.
String	getOpName() Get the symbol name (+, ! etc) for this function -- maybe null for none
int	hashCode() Expr are used in both syntax and algebra.
boolean	isFunction() Answer wether this is a function.
abstract int	numArgs()

Methods inherited from class org.apache.jena.sparql.expr.ExprNode

applyNodeTransform, asVar, copySubstitute, deepCopy, equals, equalsBySyntax, eval, getConstant, getExpr, getExprVar, getGraphPattern, getVarName, getVarNamesMentioned, getVarsMentioned, isConstant, isExpr, isGraphPattern, isSatisfied, isVariable, toString, varNamesMentioned, varsMentioned

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.jena.sparql.expr.Expr

visit

Method Detail

getArg

public abstract Expr getArg(int i)

numArgs

public abstract int numArgs()

getArgs

public List<Expr> getArgs()

isFunction

public boolean isFunction()

Description copied from interface: Expr

Answer wether this is a function.

Specified by:

isFunction in interface Expr

Overrides:

isFunction in class ExprNode

getFunction

public ExprFunction getFunction()

Description copied from interface: Expr

Get the function (returns null if not a function)

Specified by:

getFunction in interface Expr

Overrides:

getFunction in class ExprNode

hashCode

public int hashCode()

Description copied from interface: Expr

Expr are used in both syntax and algebra. There is no syntax to algebra translation step because the parser uses operator precedence to build the right evaluation structure directly.

The exceptions to this are the NOT EXISTS and EXISTS expressions which involve a query pattern. As a result there are different ways in syntax to produce the same algebra form.

Two Expr are considered equal if they are equal as algebra expressions. hashCode and equals must implement that.

There is also equalsBySyntax. Because two different syntax forms can yield the same algebra, but two different algebra forms must be different syntax, equalsBySyntax implies equals (by alegbra).

Hence, different hashCode => not equalsBySyntax.

Specified by:

hashCode in interface Expr

Specified by:

hashCode in class ExprNode

equals

public boolean equals(Expr other,
                      boolean bySyntax)

Description copied from interface: Expr

General equality operation - consider this to be 'protected'

Specified by:

equals in interface Expr

Specified by:

equals in class ExprNode

getFunctionPrintName

public String getFunctionPrintName(SerializationContext cxt)

Name used for output in SPARQL format needing functional form (no specific keyword). e.g. regexp(), custom functions, ...

getFunctionName

public String getFunctionName(SerializationContext cxt)

Name used in a functional form (i.e. SPARQL algebra). getOpName() is used in preference as a short, symbol name.

getFunctionSymbol

public FunctionLabel getFunctionSymbol()

Used to get a unique name for the function, which is intern'ed. Used in hashCode()

getFunctionIRI

public String getFunctionIRI()

URI for this function, whether custom or specification defined URI (these are keywords in the language)

getOpName

public String getOpName()

Get the symbol name (+, ! etc) for this function -- maybe null for none