net.sf.saxon.om

Interface Sequence<T extends Item<?>>

Type Parameters:

T - the type of items that can exist in the sequence

All Known Subinterfaces:

ArrayItem, AtomicSequence, ExternalObject<T>, Function, GroundedValue<T>, Item<T>, MapItem, MutableNodeInfo, NodeInfo, SiblingCountingNode, SteppingNode<N>, VirtualNode

All Known Implementing Classes:

Abs, AbsentExtensionElement, AbstractArrayItem, AbstractFunction, AbstractNodeWrapper, AbstractVirtualNode, AccessorFn, AccessorFn.DayFromDate, AccessorFn.DayFromDateTime, AccessorFn.DaysFromDuration, AccessorFn.HoursFromDateTime, AccessorFn.HoursFromDuration, AccessorFn.HoursFromTime, AccessorFn.LocalNameFromQName, AccessorFn.MinutesFromDateTime, AccessorFn.MinutesFromDuration, AccessorFn.MinutesFromTime, AccessorFn.MonthFromDate, AccessorFn.MonthFromDateTime, AccessorFn.MonthsFromDuration, AccessorFn.NamespaceUriFromQName, AccessorFn.PrefixFromQName, AccessorFn.SecondsFromDateTime, AccessorFn.SecondsFromDuration, AccessorFn.SecondsFromTime, AccessorFn.TimezoneFromDate, AccessorFn.TimezoneFromDateTime, AccessorFn.TimezoneFromTime, AccessorFn.YearFromDate, AccessorFn.YearFromDateTime, AccessorFn.YearsFromDuration, AccumulatorFn, AccumulatorFn.AccumulatorAfter, AccumulatorFn.AccumulatorBefore, Adjust_1, Adjust_2, Aggregate, AnalyzeStringFn, AnnotationParent, AnyURIValue, ApplyFn, ArrayFunctionSet.ArrayAppend, ArrayFunctionSet.ArrayFilter, ArrayFunctionSet.ArrayFlatten, ArrayFunctionSet.ArrayFoldLeft, ArrayFunctionSet.ArrayFoldRight, ArrayFunctionSet.ArrayForEach, ArrayFunctionSet.ArrayForEachPair, ArrayFunctionSet.ArrayFromSequence, ArrayFunctionSet.ArrayGet, ArrayFunctionSet.ArrayHead, ArrayFunctionSet.ArrayInsertBefore, ArrayFunctionSet.ArrayJoin, ArrayFunctionSet.ArrayPut, ArrayFunctionSet.ArrayRemove, ArrayFunctionSet.ArrayReverse, ArrayFunctionSet.ArraySize, ArrayFunctionSet.ArraySubarray, ArrayFunctionSet.ArrayTail, ArrayFunctionSet.ArrayToSequence, ArrayMember, ArrayMemberValue, ArraySort, AtomicArray, AtomicConstructorFunction, AtomicValue, AttributeImpl, AvailableEnvironmentVariables, AvailableSystemProperties, Average, AxiomAttributeWrapper, AxiomDocumentNodeWrapper, AxiomElementNodeWrapper, AxiomLeafNodeWrapper, AxiomParentNodeWrapper, Base64BinaryValue, BaseUri_1, BigDecimalValue, BigIntegerValue, Bindery.FailureValue, BooleanFn, BooleanValue, CalendarValue, CallableFunction, Ceiling, Chain, Closure, CodepointEqual, CodepointsToString, CoercedFunction, CollatingFunctionFixed, CollatingFunctionFree, CollationKeyFn, CollectionFn, CommentImpl, CompactStringValue, Compare, CompileQuery, CompileStylesheet, CompileXPath, Concat, ConstantFunction, ConstantFunction.False, ConstantFunction.True, Contains, ContainsToken, ContextAccessorFunction, ContextItemAccessorFunction, ContextItemAccessorFunction.Number_0, ContextItemAccessorFunction.StringAccessor, CopyOfFn, Count, Current, CurrentGroup, CurrentGroupingKey, CurrentMergeGroup, CurrentMergeKey, CurrentOutputUri, CurriedFunction, Data_1, DataElement, DateTimeConstructor, DateTimeValue, DateValue, DayTimeDurationValue, DecimalDivide, DecimalValue, DeepEqual, DeepEqual, DelegatingArrayItem, DelegatingMapItem, DictionaryMap, DistinctValues, Doc, Doc_2, DocAvailable, DocumentFn, DocumentImpl, DocumentInfo, DocumentUri_1, DOM4JNodeWrapper, DominoAttr, DominoNode, DOMNodeWrapper, DoubleValue, DurationValue, DynamicContextAccessor, DynamicContextAccessor.CurrentDate, DynamicContextAccessor.CurrentDateTime, DynamicContextAccessor.CurrentTime, DynamicContextAccessor.DefaultLanguage, DynamicContextAccessor.ImplicitTimezone, ElementAvailable, ElementImpl, Empty, EmptyAtomicSequence, EmptySequence, EncodeForUri, EndsWith, EnvironmentVariable, Error, EscapeHtmlUri, Eval, Evaluate, EvaluateNode, Exists, EXPathFileFunctionSet.BaseDir, ExpressionFn, ExsltCommonFunctionSet.NodeSetFn, ExsltCommonFunctionSet.ObjectTypeFn, ExtensionInstruction, FilterFn, FleetingDocumentNode, FleetingElementNode, FleetingNode, FleetingParentNode, FloatValue, Floor, FoldingFunction, FoldLeftFn, FoldRightFn, ForEachFn, ForEachPairFn, FormatDate, FormatInteger, FormatNumber, FunctionAnnotations, FunctionArity, FunctionAvailable, FunctionLookup, FunctionName, GDateValue, GDayValue, GenerateId_1, GMonthDayValue, GMonthValue, GraftedElement, GroupStarting, GYearMonthValue, GYearValue, HasChildren_1, HashTrieMap, HeadFn, HexBinaryValue, HighestOrLowest, Idref, ImmutableArrayItem, Index, IndexedValue, IndexOf, Innermost, InScopePrefixes, InsertBefore, Int64Value, IntegerRange, IntegerValue, IriToUri, IXSLFunctionSet.Call, IXSLFunctionSet.Eval, IXSLFunctionSet.ScheduleActionFn, IXSLFunctionSet.Source, IXSLFunctionSet.Stub, IXSLRemoveAttribute, IXSLScheduleAction, IXSLSetAttribute, IXSLSetProperty, IXSLSetStyle, JDOM2NodeWrapper, JDOMNodeWrapper, JsonDoc, JsonToXMLFn, KeyFn, KeyMap, Lang, LastModified, LazySequence, Leading, ListCastableFunction, ListConstructorFunction, LiteralResultElement, LoadXqueryModule, LocalName_1, LowerCase, MapCreate, MapFunctionSet.MapContains, MapFunctionSet.MapEntry, MapFunctionSet.MapFind, MapFunctionSet.MapForEach, MapFunctionSet.MapGet, MapFunctionSet.MapKeys, MapFunctionSet.MapMerge, MapFunctionSet.MapPut, MapFunctionSet.MapRemove, MapFunctionSet.MapSize, MapSearch, MapUntypedContains, Matches, MathFunctionSet.AcosFn, MathFunctionSet.AsinFn, MathFunctionSet.Atan2Fn, MathFunctionSet.AtanFn, MathFunctionSet.CosFn, MathFunctionSet.Exp10Fn, MathFunctionSet.ExpFn, MathFunctionSet.Log10Fn, MathFunctionSet.LogFn, MathFunctionSet.PiFn, MathFunctionSet.PowFn, MathFunctionSet.SinFn, MathFunctionSet.SqrtFn, MathFunctionSet.TanFn, MemoClosure, MemoFunction, MemoSequence, MessageCount, Minimax, Minimax.Max, Minimax.Min, Name_1, NamespaceForPrefix, NamespaceNode, NamespaceUri_1, NestedIntegerValue, Nilled_1, NodeImpl, NodeName_1, NormalizeSpace_1, NormalizeUnicode, NotationValue, NotFn, Number_1, NumericValue, ObjectMap, ObjectValue, One, OneOrMore, OriginalFunction, Orphan, Outermost, Parse, ParseHtml, ParseIetfDate, ParseJsonFn, ParseXml, ParseXmlFragment, ParseXPath, Path_1, PedigreeArrayItem, PedigreeFn, PedigreeMapItem, PositionAndLast, PositionAndLast.Last, PositionAndLast.Position, ProcInstImpl, Put, QNameFn, QNameValue, QualifiedNameValue, QueryFn, RandomNumberGenerator, RangeKey, RebasedNode, RegexFunction, RegexFunctionSansFlags, RegexGroup, Remove, Replace, ResolveQName, ResolveURI, Reverse, Root_1, Round, RoundHalfToEven, SaxonArray, SaxonArrayMemberInst, SaxonAssign, SaxonChange, SaxonDeepUpdate, SaxonDelete, SaxonDo, SaxonDoctype, SaxonEntityRef, SaxonImportQuery, SaxonInsert, SaxonParam, SaxonPreprocess, SaxonRename, SaxonReplace, SaxonTabulateMaps, SaxonTypeAlias, SaxonUpdate, SaxonWhile, ScalarSystemFunction, SchemaElement, SchemaFn, SearchableValue, SendMail, SequenceExtent, SequenceSlice, Serialize, Serialize, SimpleArrayItem, SingleEntryMap, SingletonClosure, SnapshotFn, SnapshotNode, Sort_1, Sort_2, Sort_3, SpaceStrippedNode, SQLClose, SQLColumn, SQLConnect, SQLConnectFn, SQLDelete, SQLDeleteFn, SQLExecute, SQLExecuteFn, SQLInsert, SQLInsertFn, SQLPreparedQueryFn, SQLPreparedStatementFn, SQLQuery, SQLQueryFn, SQLUpdate, SQLUpdateFn, StartsWith, StaticBaseUri, StaticContextAccessor, StaticContextAccessor.DefaultCollation, StaticContextAccessor.StaticBaseUri, StreamableUserFunction, StreamAvailable, StreamFn, String_1, StringJoin, StringLength_1, StringToCodepoints, StringValue, StyleElement, Subsequence_2, Subsequence_3, Substring, SubstringAfter, SubstringBefore, Sum, SuperId, SuperId.ElementWithId, SuperId.Id, SystemFunction, SystemFunctionWithBoundContextItem, SystemProperty, TailFn, TextFragmentValue, TextImpl, TextValueTemplateNode, TimestampFn, TimeValue, TinyAttributeImpl, TinyDocumentImpl, TinyElementImpl, TinyNodeImpl, TinyParentNodeImpl, TinyTextImpl, TinyTextualElement, TinyTextualElement.TinyTextualElementText, Tokenize_1, Tokenize_3, Trace, TransformFn, TransformFn, Translate, TreatFn, TreatFn.ExactlyOne, TreatFn.OneOrMore, TreatFn.ZeroOrOne, Tuple, TypeAvailable, TypeStrippedNode, UnionCastableFunction, UnionConstructorFunction, UnknownElement, Unordered, UnparsedEntity, UnparsedEntity.UnparsedEntityPublicId, UnparsedEntity.UnparsedEntityUri, UnparsedText, UnparsedTextAvailable, UnparsedTextFunction, UnparsedTextLines, UnresolvedXQueryFunctionItem, UntypedAtomicValue, UpperCase, UriCollection, UserFunction, UserFunctionReference.BoundUserFunction, ValidateFn, VendorFunctionSetHE.DynamicErrorInfoFn, VendorFunctionSetHE.HasLocalNamespaces, VendorFunctionSetHE.HasUniformNamespaces, VendorFunctionSetHE.IsWholeNumberFn, VirtualCopy, VirtualUntypedCopy, WhitespaceTextImpl, WithPedigree, XMLToJsonFn, XOMDocumentWrapper, XOMNodeWrapper, XSDAlternative, XSDAnnotation, XSDAny, XSDAnyAttribute, XSDAssert, XSDAttribute, XSDAttributeGroup, XSDComplexContent, XSDComplexContentRestriction, XSDComplexType, XSDCompositor, XSDDefaultOpenContent, XSDDocumentation, XSDElement, XSDExtension, XSDFacet, XSDFieldOrSelector, XSDGroup, XSDIdentityConstraint, XSDImport, XSDInclude, XSDList, XSDNotation, XSDOpenContent, XSDOverride, XSDRedefine, XSDSchema, XSDSimpleContent, XSDSimpleContentRestriction, XSDSimpleType, XSDSimpleTypeRestriction, XSDUnion, XSLAccept, XSLAcceptExpose, XSLAccumulator, XSLAccumulatorRule, XSLAnalyzeString, XSLApplyImports, XSLApplyTemplates, XSLAssert, XSLAttribute, XSLAttributeSet, XSLBreak, XSLBreakOrContinue, XSLCallTemplate, XSLCatch, XSLCharacterMap, XSLChoose, XSLComment, XSLContextItem, XSLCopy, XSLCopyOf, XSLDecimalFormat, XSLDocument, XSLElement, XSLEvaluate, XSLExpose, XSLFallback, XSLForEach, XSLForEachGroup, XSLFork, XSLFunction, XSLGeneralIncorporate, XSLGeneralVariable, XSLGlobalContextItem, XSLGlobalParam, XSLGlobalVariable, XSLIf, XSLImport, XSLImportSchema, XSLInclude, XSLIterate, XSLKey, XSLLeafNodeConstructor, XSLLocalParam, XSLLocalVariable, XSLMap, XSLMapEntry, XSLMatchingSubstring, XSLMerge, XSLMergeAction, XSLMergeKey, XSLMergeSource, XSLMessage, XSLMode, XSLModuleRoot, XSLNamespace, XSLNamespaceAlias, XSLNextIteration, XSLNextMatch, XSLNumber, XSLOnCompletion, XSLOnEmpty, XSLOnNonEmpty, XSLOtherwise, XSLOutput, XSLOutputCharacter, XSLOverride, XSLPackage, XSLPerformSort, XSLPreserveSpace, XSLProcessingInstruction, XSLResultDocument, XSLSequence, XSLSort, XSLSortOrMergeKey, XSLSourceDocument, XSLStylesheet, XSLTemplate, XSLText, XSLTry, XSLUsePackage, XSLValueOf, XSLWhen, XSLWherePopulated, XSLWithParam, YearMonthDurationValue, ZeroOrMore, ZeroOrOne

public interface Sequence<T extends Item<?>>

This interface represents an XDM Value, that is, a sequence of items.

Note that different implementations of Sequence might have very different performance characteristics, though all should exhibit the same behaviour. With some sequences, calling iterate() may trigger evaluation of the logic that computes the sequence, and calling iterate() again may cause re-evaluation.

Users should avoid assuming that a sequence of length one will always be represented as an instance of Item. If you are confident that the sequence will be of length one, call the head() function to get the first item.

Since:

9.5. Generified in 9.9.

Method Summary

Modifier and Type	Method and Description
default java.lang.Iterable<T>	asIterable() Get the contents of this value in the form of a Java Iterable, so that it can be used in a for-each expression.
T	head() Get the first item in the sequence.
SequenceIterator<T>	iterate() Get a SequenceIterator over all the items in the sequence
default Sequence<T>	makeRepeatable() Ensure that the sequence is in a form where it can be evaluated more than once.
default GroundedValue<T>	materialize() Create a GroundedValue containing the same items as this Sequence.

Method Detail

head

T head()
throws XPathException

Get the first item in the sequence.

Returns:

the first item in the sequence if there is one, or null if the sequence is empty

Throws:

XPathException - in the situation where the sequence is evaluated lazily, and evaluation of the first item causes a dynamic error.

iterate

SequenceIterator<T> iterate()
                     throws XPathException

Get a SequenceIterator over all the items in the sequence

Returns:

an iterator (specifically, a Saxon SequenceIterator, which is not a Iterator) over all the items

Throws:

XPathException - in the situation where the sequence is evaluated lazily, and constructing an iterator over the items causes a dynamic error.

asIterable

default java.lang.Iterable<T> asIterable()
                                  throws XPathException

Get the contents of this value in the form of a Java Iterable, so that it can be used in a for-each expression. In the general case, obtaining the iterable may raise dynamic errors; but the Iterator obtained from the iterable will be error-free. Subclasses of Sequence that implement GroundedValue are directly iterable, so this method is a no-op in those cases.

Returns:

an Iterable containing the same sequence of items

Throws:

XPathException

materialize

default GroundedValue<T> materialize()
                              throws XPathException

Create a GroundedValue containing the same items as this Sequence. A GroundedValue typically contains the entire sequence in memory; at any rate, it guarantees that the entire sequence can be read without any possibility of XPath dynamic errors arising.

Returns:

a GroundedValue containing the same items as this Sequence

Throws:

XPathException - if evaluating the contents of the sequence fails with a dynamic error.

makeRepeatable

default Sequence<T> makeRepeatable()
                            throws XPathException

Ensure that the sequence is in a form where it can be evaluated more than once. Some sequences (for example LazySequence and Closure can only be evaluated once, and this operation causes these to be grounded. However, making it repeatable is not the same as making it grounded; it does not flush out all errors. Indeed, lazy evaluation relies on this property, because an expression that has been lifted out of a loop must not be evaluated unless the loop is executed at least once, to prevent spurious errors.

Returns:

An equivalent sequence that can be repeatedly evaluated

Throws:

XPathException - if evaluation fails