Package org.basex.query.func.fn

Class FnEmpty

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.Arr

org.basex.query.func.StandardFunc

org.basex.query.func.fn.FnEmpty

Direct Known Subclasses:

FnExists

public class FnEmpty
extends StandardFunc

Function implementation.

Author:

BaseX Team 2005-24, BSD License, Christian Gruen

Field Summary

Fields inherited from class org.basex.query.func.StandardFunc

definition

Fields inherited from class org.basex.query.expr.Arr

exprs

Fields inherited from class org.basex.query.expr.ParseExpr

exprType, info

Constructor Summary

Constructors

Constructor	Description
FnEmpty()

Method Summary

Modifier and Type	Method	Description
Bln	item(QueryContext qc, InputInfo ii)	Evaluates the expression and returns the resulting item, or Empty.VALUE if the expression yields an empty sequence.
Expr	mergeEbv(Expr expr, boolean or, CompileContext cc)	Tries to merge two expressions that are part of an EBV test.
protected Expr	opt(CompileContext cc)	Performs function-specific optimizations.
protected void	simplifyArgs(CompileContext cc)	Simplifies the types of all arguments.

Methods inherited from class org.basex.query.func.StandardFunc

arity, checkPerm, coerce, coerce, compileData, copy, dataLock, defined, description, embed, equals, has, hasCTX, hasUPD, hofIndex, optFirst, optFirst, optimize, refineFunc, serialize, toBaseUri, toBindings, toBoolean, toCollation, toCollation, toContent, toContent, toData, toDate, toDBNode, toEncodingOrNull, toEncodingOrNull, toFunction, toFunction, toFunctionOrNull, toIO, toIO, toMs, toName, toNodeOrAtomItem, toOptions, toOptions, toPath, toPath, toStr, toString, toXml, toZeroStr, vacuous, variadic

Methods inherited from class org.basex.query.expr.Arr

accept, allAreValues, arg, args, checkUp, compile, copyAll, count, exprSize, flatten, inline, inlineable, mayBePositional, removeEmpty, simplifyAll

Methods inherited from class org.basex.query.expr.ParseExpr

adoptType, atomValue, checkAllUp, checkNoneUp, checkNoUp, checkType, checkType, checkUp, copyType, ctxValue, data, info, iter, refineType, sc, seqType, size, test, toArray, toArray, toAtomItem, toBin, toBin, toBinOrNull, toBoolean, toBoolean, toBooleanOrFalse, toBytes, toBytes, toDouble, toDouble, toElem, toElem, toEnum, toFloat, toFunction, toLong, toLong, toLong, toMap, toMap, toNode, toNode, toNodeOrNull, toNumber, toNumber, toNumberOrNull, toQNm, toQNmOrNull, toRecord, toString, toString, toStringOrNull, toToken, toToken, toTokenOrNull, toZeroToken, value

Methods inherited from class org.basex.query.expr.Expr

arg, atomItem, atomIter, ddo, funcType, hasFreeVars, indexAccessible, info, isSimple, markTailCalls, optimizePos, simplify, simplifyFor, typeCheck, uses, visitAll

Methods inherited from class org.basex.query.expr.ExprInfo

toErrorString, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

FnEmpty

public FnEmpty()

Method Detail

item

public Bln item(QueryContext qc,
                InputInfo ii)
         throws QueryException

Description copied from class: Expr

Evaluates the expression and returns the resulting item, or Empty.VALUE if the expression yields an empty sequence. If this method is not implemented, Expr.value(QueryContext) must be implemented instead.

Overrides:

item in class ParseExpr

Parameters:

qc - query context

ii - input info (can be null); required for those Value instances that have no input info)

Returns:

item or Empty.VALUE

Throws:

QueryException - query exception

simplifyArgs

protected final void simplifyArgs(CompileContext cc)
                           throws QueryException

Description copied from class: StandardFunc

Simplifies the types of all arguments. This function is overwritten by functions that rely on the original argument type.

Overrides:

simplifyArgs in class StandardFunc

Parameters:

cc - compilation context

Throws:

QueryException - query exception

opt

protected final Expr opt(CompileContext cc)
                  throws QueryException

Description copied from class: StandardFunc

Performs function-specific optimizations.

Overrides:

opt in class StandardFunc

Parameters:

cc - compilation context

Returns:

optimized or original expression

Throws:

QueryException - query exception

mergeEbv

public final Expr mergeEbv(Expr expr,
                           boolean or,
                           CompileContext cc)
                    throws QueryException

Description copied from class: Expr

Tries to merge two expressions that are part of an EBV test. Called by And, Or), Step and Filter. Overwritten by CmpG, CmpIR, CmpR, CmpSR, IntPos, SimplePos and others.

Overrides:

mergeEbv in class Expr

Parameters:

expr - second expression

or - union or intersection

cc - compilation context

Returns:

optimized expression or null

Throws:

QueryException - query exception