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java.lang.Objectorg.basex.data.ExprInfo
org.basex.query.expr.Expr
org.basex.query.value.Value
org.basex.query.value.seq.Empty
public final class Empty
Empty sequence.
Nested Class Summary |
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Nested classes/interfaces inherited from class org.basex.query.expr.Expr |
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Expr.Flag |
Field Summary | |
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static ValueIter |
ITER
Empty iterator. |
static Empty |
SEQ
Single instance. |
Fields inherited from class org.basex.query.value.Value |
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type |
Method Summary | |
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java.lang.String |
description()
Returns a string description of the expression. |
Item |
ebv(QueryContext ctx,
InputInfo ii)
Checks if the iterator can be dissolved into an effective boolean value. |
int |
hash(InputInfo ii)
Returns a hash code for this value. |
boolean |
homogeneous()
Checks if all items of this value share the same type. |
boolean |
isEmpty()
Tests if this is an empty sequence. |
boolean |
isVacuous()
Tests if this is a vacuous expression (empty sequence or error function). |
Item |
item(QueryContext ctx,
InputInfo ii)
Evaluates the expression and returns the resulting item or a null reference, if the expression yields an empty sequence. |
Item |
itemAt(long pos)
Gets the item at the given position in the value. |
ValueIter |
iter()
Returns an iterator. |
boolean |
iterable()
Returns true if the expression is iterable, i.e., if it will not contain any duplicate nodes and if all nodes will be are sorted. |
void |
plan(FElem plan)
Creates an expression tree. |
long |
size()
Returns the sequence size or 1. |
Item |
test(QueryContext ctx,
InputInfo ii)
Performs a predicate test and returns the item if test was successful. |
java.lang.Object |
toJava()
Returns a Java representation of the value. |
java.lang.String |
toString()
|
SeqType |
type()
Returns the static type of the evaluated value. |
int |
writeTo(Item[] arr,
int start)
Writes this value's items out to the given array. |
Methods inherited from class org.basex.query.value.Value |
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accept, cache, checkUp, compile, copy, count, data, exprSize, has, inline, isValue, iter, iterator, removable, serialize, value |
Methods inherited from class org.basex.query.expr.Expr |
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addText, compEbv, copy, hasFreeVars, indexAccessible, indexEquivalent, inlineAll, isFunction, isItem, markTailCalls, optimize, sameAs, uses, visitAll |
Methods inherited from class org.basex.data.ExprInfo |
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addPlan, addPlan, info, planAttr, planElem |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Field Detail |
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public static final Empty SEQ
public static final ValueIter ITER
Method Detail |
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public boolean isEmpty()
Expr
Empty
class, which represents the empty sequence.
isEmpty
in class Expr
public boolean isVacuous()
Expr
isVacuous
in class Expr
public long size()
Expr
size
in class Value
public java.lang.Object toJava()
Value
toJava
in class Value
public ValueIter iter()
Value
iter
in class Value
public Item item(QueryContext ctx, InputInfo ii)
Expr
null
reference, if the expression yields an empty sequence.
If this method is not overwritten, Expr.iter(org.basex.query.QueryContext)
must be implemented
by an expression, as it may be called by this method.
item
in class Expr
ctx
- query contextii
- input info
public Item ebv(QueryContext ctx, InputInfo ii)
Expr
ebv
in class Expr
ctx
- query contextii
- input info
public Item test(QueryContext ctx, InputInfo ii)
Expr
test
in class Expr
ctx
- query contextii
- input info
public SeqType type()
Expr
type
in class Expr
public boolean iterable()
Expr
AxisPath
.
iterable
in class Expr
public void plan(FElem plan)
ExprInfo
plan
in class ExprInfo
plan
- root elementpublic int hash(InputInfo ii)
Value
hash
in class Value
ii
- input info
public java.lang.String description()
ExprInfo
ExprInfo.toString()
method,
arguments are not included in the output.
description
in class Value
public java.lang.String toString()
toString
in class ExprInfo
public int writeTo(Item[] arr, int start)
Value
writeTo
in class Value
arr
- array to write tostart
- start position
public Item itemAt(long pos)
Value
itemAt
in class Value
pos
- position
public boolean homogeneous()
Value
homogeneous
in class Value
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