# ## Module xpathInternals from libxml2

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internal interfaces for XML Path Language implementation used to build new modules on top of XPath like XPointer and XSLT ## Table of Contents
    #define CAST_TO_BOOLEAN
    #define CAST_TO_NUMBER
    #define CAST_TO_STRING
    #define CHECK_ARITY
    #define CHECK_ERROR
    #define CHECK_ERROR0
    #define CHECK_TYPE
    #define CHECK_TYPE0
    #define XP_ERROR
    #define XP_ERROR0
    #define xmlXPathCheckError
    #define xmlXPathEmptyNodeSet
    #define xmlXPathGetContextNode
    #define xmlXPathGetDocument
    #define xmlXPathGetError
    #define xmlXPathReturnBoolean
    #define xmlXPathReturnEmptyNodeSet
    #define xmlXPathReturnEmptyString
    #define xmlXPathReturnExternal
    #define xmlXPathReturnFalse
    #define xmlXPathReturnNodeSet
    #define xmlXPathReturnNumber
    #define xmlXPathReturnString
    #define xmlXPathReturnTrue
    #define xmlXPathSetArityError
    #define xmlXPathSetError
    #define xmlXPathSetTypeError
    #define xmlXPathStackIsExternal
    #define xmlXPathStackIsNodeSet
    xmlXPathObjectPtr	valuePop	(xmlXPathParserContextPtr ctxt)
    int	valuePush			(xmlXPathParserContextPtr ctxt,
    					 xmlXPathObjectPtr value)
    void	xmlXPathAddValues		(xmlXPathParserContextPtr ctxt)
    void	xmlXPathBooleanFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathCeilingFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    int	xmlXPathCompareValues		(xmlXPathParserContextPtr ctxt,
    					 int inf,
    					 int strict)
    void	xmlXPathConcatFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathContainsFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathCountFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathDebugDumpCompExpr	(FILE * output,
    					 xmlXPathCompExprPtr comp,
    					 int depth)
    void	xmlXPathDebugDumpObject		(FILE * output,
    					 xmlXPathObjectPtr cur,
    					 int depth)
    xmlNodeSetPtr	xmlXPathDifference	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
    xmlNodeSetPtr	xmlXPathDistinct	(xmlNodeSetPtr nodes)
    xmlNodeSetPtr	xmlXPathDistinctSorted	(xmlNodeSetPtr nodes)
    void	xmlXPathDivValues		(xmlXPathParserContextPtr ctxt)
    int	xmlXPathEqualValues		(xmlXPathParserContextPtr ctxt)
    void	xmlXPathErr			(xmlXPathParserContextPtr ctxt,
    					 int error)
    void	xmlXPathEvalExpr		(xmlXPathParserContextPtr ctxt)
    int	xmlXPathEvaluatePredicateResult	(xmlXPathParserContextPtr ctxt,
    					 xmlXPathObjectPtr res)
    void	xmlXPathFalseFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathFloorFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathFreeParserContext	(xmlXPathParserContextPtr ctxt)
    xmlXPathFunction	xmlXPathFunctionLookup	(xmlXPathContextPtr ctxt,
    						 const xmlChar * name)
    xmlXPathFunction	xmlXPathFunctionLookupNS	(xmlXPathContextPtr ctxt,
    							 const xmlChar * name,
    							 const xmlChar * ns_uri)
    int	xmlXPathHasSameNodes		(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
    void	xmlXPathIdFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    xmlNodeSetPtr	xmlXPathIntersection	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
    int	xmlXPathIsNodeType		(const xmlChar * name)
    void	xmlXPathLangFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathLastFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    xmlNodeSetPtr	xmlXPathLeading		(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
    xmlNodeSetPtr	xmlXPathLeadingSorted	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
    void	xmlXPathLocalNameFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathModValues		(xmlXPathParserContextPtr ctxt)
    void	xmlXPathMultValues		(xmlXPathParserContextPtr ctxt)
    void	xmlXPathNamespaceURIFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    xmlXPathObjectPtr	xmlXPathNewBoolean	(int val)
    xmlXPathObjectPtr	xmlXPathNewCString	(const char * val)
    xmlXPathObjectPtr	xmlXPathNewFloat	(double val)
    xmlXPathObjectPtr	xmlXPathNewNodeSet	(xmlNodePtr val)
    xmlXPathObjectPtr	xmlXPathNewNodeSetList	(xmlNodeSetPtr val)
    xmlXPathParserContextPtr	xmlXPathNewParserContext	(const xmlChar * str,
    							 xmlXPathContextPtr ctxt)
    xmlXPathObjectPtr	xmlXPathNewString	(const xmlChar * val)
    xmlXPathObjectPtr	xmlXPathNewValueTree	(xmlNodePtr val)
    xmlNodePtr	xmlXPathNextAncestor	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextAncestorOrSelf	(xmlXPathParserContextPtr ctxt,
    						 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextAttribute	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextChild	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextDescendant	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextDescendantOrSelf	(xmlXPathParserContextPtr ctxt,
    						 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextFollowing	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextFollowingSibling	(xmlXPathParserContextPtr ctxt,
    						 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextNamespace	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextParent	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextPreceding	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextPrecedingSibling	(xmlXPathParserContextPtr ctxt,
    						 xmlNodePtr cur)
    xmlNodePtr	xmlXPathNextSelf	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
    xmlNodeSetPtr	xmlXPathNodeLeading	(xmlNodeSetPtr nodes,
    					 xmlNodePtr node)
    xmlNodeSetPtr	xmlXPathNodeLeadingSorted	(xmlNodeSetPtr nodes,
    						 xmlNodePtr node)
    int	xmlXPathNodeSetAdd		(xmlNodeSetPtr cur,
    					 xmlNodePtr val)
    int	xmlXPathNodeSetAddNs		(xmlNodeSetPtr cur,
    					 xmlNodePtr node,
    					 xmlNsPtr ns)
    int	xmlXPathNodeSetAddUnique	(xmlNodeSetPtr cur,
    					 xmlNodePtr val)
    int	xmlXPathNodeSetContains		(xmlNodeSetPtr cur,
    					 xmlNodePtr val)
    void	xmlXPathNodeSetDel		(xmlNodeSetPtr cur,
    					 xmlNodePtr val)
    void	xmlXPathNodeSetFreeNs		(xmlNsPtr ns)
    xmlNodeSetPtr	xmlXPathNodeSetMerge	(xmlNodeSetPtr val1,
    					 xmlNodeSetPtr val2)
    void	xmlXPathNodeSetRemove		(xmlNodeSetPtr cur,
    					 int val)
    void	xmlXPathNodeSetSort		(xmlNodeSetPtr set)
    xmlNodeSetPtr	xmlXPathNodeTrailing	(xmlNodeSetPtr nodes,
    					 xmlNodePtr node)
    xmlNodeSetPtr	xmlXPathNodeTrailingSorted	(xmlNodeSetPtr nodes,
    						 xmlNodePtr node)
    void	xmlXPathNormalizeFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    int	xmlXPathNotEqualValues		(xmlXPathParserContextPtr ctxt)
    void	xmlXPathNotFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    const xmlChar *	xmlXPathNsLookup	(xmlXPathContextPtr ctxt,
    					 const xmlChar * prefix)
    void	xmlXPathNumberFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    xmlChar *	xmlXPathParseNCName	(xmlXPathParserContextPtr ctxt)
    xmlChar *	xmlXPathParseName	(xmlXPathParserContextPtr ctxt)
    int	xmlXPathPopBoolean		(xmlXPathParserContextPtr ctxt)
    void *	xmlXPathPopExternal		(xmlXPathParserContextPtr ctxt)
    xmlNodeSetPtr	xmlXPathPopNodeSet	(xmlXPathParserContextPtr ctxt)
    double	xmlXPathPopNumber		(xmlXPathParserContextPtr ctxt)
    xmlChar *	xmlXPathPopString	(xmlXPathParserContextPtr ctxt)
    void	xmlXPathPositionFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathRegisterAllFunctions	(xmlXPathContextPtr ctxt)
    int	xmlXPathRegisterFunc		(xmlXPathContextPtr ctxt,
    					 const xmlChar * name,
    					 xmlXPathFunction f)
    void	xmlXPathRegisterFuncLookup	(xmlXPathContextPtr ctxt,
    					 xmlXPathFuncLookupFunc f,
    					 void * funcCtxt)
    int	xmlXPathRegisterFuncNS		(xmlXPathContextPtr ctxt,
    					 const xmlChar * name,
    					 const xmlChar * ns_uri,
    					 xmlXPathFunction f)
    int	xmlXPathRegisterNs		(xmlXPathContextPtr ctxt,
    					 const xmlChar * prefix,
    					 const xmlChar * ns_uri)
    int	xmlXPathRegisterVariable	(xmlXPathContextPtr ctxt,
    					 const xmlChar * name,
    					 xmlXPathObjectPtr value)
    void	xmlXPathRegisterVariableLookup	(xmlXPathContextPtr ctxt,
    					 xmlXPathVariableLookupFunc f,
    					 void * data)
    int	xmlXPathRegisterVariableNS	(xmlXPathContextPtr ctxt,
    					 const xmlChar * name,
    					 const xmlChar * ns_uri,
    					 xmlXPathObjectPtr value)
    void	xmlXPathRegisteredFuncsCleanup	(xmlXPathContextPtr ctxt)
    void	xmlXPathRegisteredNsCleanup	(xmlXPathContextPtr ctxt)
    void	xmlXPathRegisteredVariablesCleanup	(xmlXPathContextPtr ctxt)
    void	xmlXPathRoot			(xmlXPathParserContextPtr ctxt)
    void	xmlXPathRoundFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathStartsWithFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    double	xmlXPathStringEvalNumber	(const xmlChar * str)
    void	xmlXPathStringFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathStringLengthFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathSubValues		(xmlXPathParserContextPtr ctxt)
    void	xmlXPathSubstringAfterFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathSubstringBeforeFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathSubstringFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathSumFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    xmlNodeSetPtr	xmlXPathTrailing	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
    xmlNodeSetPtr	xmlXPathTrailingSorted	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
    void	xmlXPathTranslateFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathTrueFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
    void	xmlXPathValueFlipSign		(xmlXPathParserContextPtr ctxt)
    xmlXPathObjectPtr	xmlXPathVariableLookup	(xmlXPathContextPtr ctxt,
    						 const xmlChar * name)
    xmlXPathObjectPtr	xmlXPathVariableLookupNS	(xmlXPathContextPtr ctxt,
    							 const xmlChar * name,
    							 const xmlChar * ns_uri)
    xmlXPathObjectPtr	xmlXPathWrapCString	(char * val)
    xmlXPathObjectPtr	xmlXPathWrapExternal	(void * val)
    xmlXPathObjectPtr	xmlXPathWrapNodeSet	(xmlNodeSetPtr val)
    xmlXPathObjectPtr	xmlXPathWrapString	(xmlChar * val)
    void	xmlXPatherror			(xmlXPathParserContextPtr ctxt,
    					 const char * file,
    					 int line,
    					 int no)
## Description ### Macro: CAST_TO_BOOLEAN
    #define CAST_TO_BOOLEAN
Macro to try to cast the value on the top of the XPath stack to a boolean. ### Macro: CAST_TO_NUMBER
    #define CAST_TO_NUMBER
Macro to try to cast the value on the top of the XPath stack to a number. ### Macro: CAST_TO_STRING
    #define CAST_TO_STRING
Macro to try to cast the value on the top of the XPath stack to a string. ### Macro: CHECK_ARITY
    #define CHECK_ARITY
Macro to check that the number of args passed to an XPath function matches. ### Macro: CHECK_ERROR
    #define CHECK_ERROR
Macro to return from the function if an XPath error was detected. ### Macro: CHECK_ERROR0
    #define CHECK_ERROR0
Macro to return 0 from the function if an XPath error was detected. ### Macro: CHECK_TYPE
    #define CHECK_TYPE
Macro to check that the value on top of the XPath stack is of a given type. ### Macro: CHECK_TYPE0
    #define CHECK_TYPE0
Macro to check that the value on top of the XPath stack is of a given type. Return(0) in case of failure ### Macro: XP_ERROR
    #define XP_ERROR
Macro to raise an XPath error and return. ### Macro: XP_ERROR0
    #define XP_ERROR0
Macro to raise an XPath error and return 0. ### Macro: xmlXPathCheckError
    #define xmlXPathCheckError
Check if an XPath error was raised. Returns true if an error has been raised, false otherwise. ### Macro: xmlXPathEmptyNodeSet
    #define xmlXPathEmptyNodeSet
Empties a node-set. ### Macro: xmlXPathGetContextNode
    #define xmlXPathGetContextNode
Get the context node of an XPath context. Returns the context node. ### Macro: xmlXPathGetDocument
    #define xmlXPathGetDocument
Get the document of an XPath context. Returns the context document. ### Macro: xmlXPathGetError
    #define xmlXPathGetError
Get the error code of an XPath context. Returns the context error. ### Macro: xmlXPathReturnBoolean
    #define xmlXPathReturnBoolean
Pushes the boolean @val on the context stack. ### Macro: xmlXPathReturnEmptyNodeSet
    #define xmlXPathReturnEmptyNodeSet
Pushes an empty node-set on the context stack. ### Macro: xmlXPathReturnEmptyString
    #define xmlXPathReturnEmptyString
Pushes an empty string on the stack. ### Macro: xmlXPathReturnExternal
    #define xmlXPathReturnExternal
Pushes user data on the context stack. ### Macro: xmlXPathReturnFalse
    #define xmlXPathReturnFalse
Pushes false on the context stack. ### Macro: xmlXPathReturnNodeSet
    #define xmlXPathReturnNodeSet
Pushes the node-set @ns on the context stack. ### Macro: xmlXPathReturnNumber
    #define xmlXPathReturnNumber
Pushes the double @val on the context stack. ### Macro: xmlXPathReturnString
    #define xmlXPathReturnString
Pushes the string @str on the context stack. ### Macro: xmlXPathReturnTrue
    #define xmlXPathReturnTrue
Pushes true on the context stack. ### Macro: xmlXPathSetArityError
    #define xmlXPathSetArityError
Raises an XPATH_INVALID_ARITY error. ### Macro: xmlXPathSetError
    #define xmlXPathSetError
Raises an error. ### Macro: xmlXPathSetTypeError
    #define xmlXPathSetTypeError
Raises an XPATH_INVALID_TYPE error. ### Macro: xmlXPathStackIsExternal
    #define xmlXPathStackIsExternal
Checks if the current value on the XPath stack is an external object. Returns true if the current object on the stack is an external object. ### Macro: xmlXPathStackIsNodeSet
    #define xmlXPathStackIsNodeSet
Check if the current value on the XPath stack is a node set or an XSLT value tree. Returns true if the current object on the stack is a node-set. ### Function: valuePop
    xmlXPathObjectPtr	valuePop	(xmlXPathParserContextPtr ctxt)
Pops the top XPath object from the value stack
`ctxt`: | an XPath evaluation context
`Returns`: | the XPath object just removed
### Function: valuePush
    int	valuePush			(xmlXPathParserContextPtr ctxt,
    					 xmlXPathObjectPtr value)
Pushes a new XPath object on top of the value stack
`ctxt`: | an XPath evaluation context
`value`: | the XPath object
`Returns`: | the number of items on the value stack
### Function: xmlXPathAddValues
    void	xmlXPathAddValues		(xmlXPathParserContextPtr ctxt)
Implement the add operation on XPath objects: The numeric operators convert their operands to numbers as if by calling the number function.
`ctxt`: | the XPath Parser context
### Function: xmlXPathBooleanFunction
    void	xmlXPathBooleanFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the boolean() XPath function boolean boolean(object) The boolean function converts its argument to a boolean as follows: - a number is true if and only if it is neither positive or negative zero nor NaN - a node-set is true if and only if it is non-empty - a string is true if and only if its length is non-zero
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathCeilingFunction
    void	xmlXPathCeilingFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the ceiling() XPath function number ceiling(number) The ceiling function returns the smallest (closest to negative infinity) number that is not less than the argument and that is an integer.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathCompareValues
    int	xmlXPathCompareValues		(xmlXPathParserContextPtr ctxt,
    					 int inf,
    					 int strict)
Implement the compare operation on XPath objects: @arg1 < @arg2 (1, 1, ... @arg1 <= @arg2 (1, 0, ... @arg1 > @arg2 (0, 1, ... @arg1 >= @arg2 (0, 0, ... When neither object to be compared is a node-set and the operator is <=, <, >=, >, then the objects are compared by converted both objects to numbers and comparing the numbers according to IEEE 754. The < comparison will be true if and only if the first number is less than the second number. The <= comparison will be true if and only if the first number is less than or equal to the second number. The > comparison will be true if and only if the first number is greater than the second number. The >= comparison will be true if and only if the first number is greater than or equal to the second number.
`ctxt`: | the XPath Parser context
`inf`: | less than (1) or greater than (0)
`strict`: | is the comparison strict
`Returns`: | 1 if the comparison succeeded, 0 if it failed
### Function: xmlXPathConcatFunction
    void	xmlXPathConcatFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the concat() XPath function string concat(string, string, string*) The concat function returns the concatenation of its arguments.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathContainsFunction
    void	xmlXPathContainsFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the contains() XPath function boolean contains(string, string) The contains function returns true if the first argument string contains the second argument string, and otherwise returns false.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathCountFunction
    void	xmlXPathCountFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the count() XPath function number count(node-set)
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathDebugDumpCompExpr
    void	xmlXPathDebugDumpCompExpr	(FILE * output,
    					 xmlXPathCompExprPtr comp,
    					 int depth)
Dumps the tree of the compiled XPath expression.
`output`: | the FILE * for the output
`comp`: | the precompiled XPath expression
`depth`: | the indentation level.
### Function: xmlXPathDebugDumpObject
    void	xmlXPathDebugDumpObject		(FILE * output,
    					 xmlXPathObjectPtr cur,
    					 int depth)
Dump the content of the object for debugging purposes
`output`: | the FILE * to dump the output
`cur`: | the object to inspect
`depth`: | indentation level
### Function: xmlXPathDifference
    xmlNodeSetPtr	xmlXPathDifference	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
Implements the EXSLT - Sets difference() function: node-set set:difference (node-set, node-set)
`nodes1`: | a node-set
`nodes2`: | a node-set
`Returns`: | the difference between the two node sets, or nodes1 if nodes2 is empty
### Function: xmlXPathDistinct
    xmlNodeSetPtr	xmlXPathDistinct	(xmlNodeSetPtr nodes)
Implements the EXSLT - Sets distinct() function: node-set set:distinct (node-set) @nodes is sorted by document order, then #exslSetsDistinctSorted is called with the sorted node-set
`nodes`: | a node-set
`Returns`: | a subset of the nodes contained in @nodes, or @nodes if it is empty
### Function: xmlXPathDistinctSorted
    xmlNodeSetPtr	xmlXPathDistinctSorted	(xmlNodeSetPtr nodes)
Implements the EXSLT - Sets distinct() function: node-set set:distinct (node-set)
`nodes`: | a node-set, sorted by document order
`Returns`: | a subset of the nodes contained in @nodes, or @nodes if it is empty
### Function: xmlXPathDivValues
    void	xmlXPathDivValues		(xmlXPathParserContextPtr ctxt)
Implement the div operation on XPath objects @arg1 / @arg2: The numeric operators convert their operands to numbers as if by calling the number function.
`ctxt`: | the XPath Parser context
### Function: xmlXPathEqualValues
    int	xmlXPathEqualValues		(xmlXPathParserContextPtr ctxt)
Implement the equal operation on XPath objects content: @arg1 == @arg2
`ctxt`: | the XPath Parser context
`Returns`: | 0 or 1 depending on the results of the test.
### Function: xmlXPathErr
    void	xmlXPathErr			(xmlXPathParserContextPtr ctxt,
    					 int error)
Handle an XPath error
`ctxt`: | a XPath parser context
`error`: | the error code
### Function: xmlXPathEvalExpr
    void	xmlXPathEvalExpr		(xmlXPathParserContextPtr ctxt)
Parse and evaluate an XPath expression in the given context, then push the result on the context stack
`ctxt`: | the XPath Parser context
### Function: xmlXPathEvaluatePredicateResult
    int	xmlXPathEvaluatePredicateResult	(xmlXPathParserContextPtr ctxt,
    					 xmlXPathObjectPtr res)
Evaluate a predicate result for the current node. A PredicateExpr is evaluated by evaluating the Expr and converting the result to a boolean. If the result is a number, the result will be converted to true if the number is equal to the position of the context node in the context node list (as returned by the position function) and will be converted to false otherwise; if the result is not a number, then the result will be converted as if by a call to the boolean function.
`ctxt`: | the XPath Parser context
`res`: | the Predicate Expression evaluation result
`Returns`: | 1 if predicate is true, 0 otherwise
### Function: xmlXPathFalseFunction
    void	xmlXPathFalseFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the false() XPath function boolean false()
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathFloorFunction
    void	xmlXPathFloorFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the floor() XPath function number floor(number) The floor function returns the largest (closest to positive infinity) number that is not greater than the argument and that is an integer.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathFreeParserContext
    void	xmlXPathFreeParserContext	(xmlXPathParserContextPtr ctxt)
Free up an xmlXPathParserContext
`ctxt`: | the context to free
### Function: xmlXPathFunctionLookup
    xmlXPathFunction	xmlXPathFunctionLookup	(xmlXPathContextPtr ctxt,
    						 const xmlChar * name)
Search in the Function array of the context for the given function.
`ctxt`: | the XPath context
`name`: | the function name
`Returns`: | the xmlXPathFunction or NULL if not found
### Function: xmlXPathFunctionLookupNS
    xmlXPathFunction	xmlXPathFunctionLookupNS	(xmlXPathContextPtr ctxt,
    							 const xmlChar * name,
    							 const xmlChar * ns_uri)
Search in the Function array of the context for the given function.
`ctxt`: | the XPath context
`name`: | the function name
`ns_uri`: | the function namespace URI
`Returns`: | the xmlXPathFunction or NULL if not found
### Function: xmlXPathHasSameNodes
    int	xmlXPathHasSameNodes		(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
Implements the EXSLT - Sets has-same-nodes function: boolean set:has-same-node(node-set, node-set)
`nodes1`: | a node-set
`nodes2`: | a node-set
`Returns`: | true (1) if @nodes1 shares any node with @nodes2, false (0) otherwise
### Function: xmlXPathIdFunction
    void	xmlXPathIdFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the id() XPath function node-set id(object) The id function selects elements by their unique ID (see [5.2.1 Unique IDs]). When the argument to id is of type node-set, then the result is the union of the result of applying id to the string value of each of the nodes in the argument node-set. When the argument to id is of any other type, the argument is converted to a string as if by a call to the string function; the string is split into a whitespace-separated list of tokens (whitespace is any sequence of characters matching the production S); the result is a node-set containing the elements in the same document as the context node that have a unique ID equal to any of the tokens in the list.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathIntersection
    xmlNodeSetPtr	xmlXPathIntersection	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
Implements the EXSLT - Sets intersection() function: node-set set:intersection (node-set, node-set)
`nodes1`: | a node-set
`nodes2`: | a node-set
`Returns`: | a node set comprising the nodes that are within both the node sets passed as arguments
### Function: xmlXPathIsNodeType
    int	xmlXPathIsNodeType		(const xmlChar * name)
Is the name given a NodeType one. [38] NodeType ::= 'comment' | 'text' | 'processing-instruction' | 'node'
`name`: | a name string
`Returns`: | 1 if true 0 otherwise
### Function: xmlXPathLangFunction
    void	xmlXPathLangFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the lang() XPath function boolean lang(string) The lang function returns true or false depending on whether the language of the context node as specified by xml:lang attributes is the same as or is a sublanguage of the language specified by the argument string. The language of the context node is determined by the value of the xml:lang attribute on the context node, or, if the context node has no xml:lang attribute, by the value of the xml:lang attribute on the nearest ancestor of the context node that has an xml:lang attribute. If there is no such attribute, then lang
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathLastFunction
    void	xmlXPathLastFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the last() XPath function number last() The last function returns the number of nodes in the context node list.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathLeading
    xmlNodeSetPtr	xmlXPathLeading		(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
Implements the EXSLT - Sets leading() function: node-set set:leading (node-set, node-set) @nodes1 and @nodes2 are sorted by document order, then #exslSetsLeadingSorted is called.
`nodes1`: | a node-set
`nodes2`: | a node-set
`Returns`: | the nodes in @nodes1 that precede the first node in @nodes2 in document order, @nodes1 if @nodes2 is NULL or empty or an empty node-set if @nodes1 doesn't contain @nodes2
### Function: xmlXPathLeadingSorted
    xmlNodeSetPtr	xmlXPathLeadingSorted	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
Implements the EXSLT - Sets leading() function: node-set set:leading (node-set, node-set)
`nodes1`: | a node-set, sorted by document order
`nodes2`: | a node-set, sorted by document order
`Returns`: | the nodes in @nodes1 that precede the first node in @nodes2 in document order, @nodes1 if @nodes2 is NULL or empty or an empty node-set if @nodes1 doesn't contain @nodes2
### Function: xmlXPathLocalNameFunction
    void	xmlXPathLocalNameFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the local-name() XPath function string local-name(node-set?) The local-name function returns a string containing the local part of the name of the node in the argument node-set that is first in document order. If the node-set is empty or the first node has no name, an empty string is returned. If the argument is omitted it defaults to the context node.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathModValues
    void	xmlXPathModValues		(xmlXPathParserContextPtr ctxt)
Implement the mod operation on XPath objects: @arg1 / @arg2 The numeric operators convert their operands to numbers as if by calling the number function.
`ctxt`: | the XPath Parser context
### Function: xmlXPathMultValues
    void	xmlXPathMultValues		(xmlXPathParserContextPtr ctxt)
Implement the multiply operation on XPath objects: The numeric operators convert their operands to numbers as if by calling the number function.
`ctxt`: | the XPath Parser context
### Function: xmlXPathNamespaceURIFunction
    void	xmlXPathNamespaceURIFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the namespace-uri() XPath function string namespace-uri(node-set?) The namespace-uri function returns a string containing the namespace URI of the expanded name of the node in the argument node-set that is first in document order. If the node-set is empty, the first node has no name, or the expanded name has no namespace URI, an empty string is returned. If the argument is omitted it defaults to the context node.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathNewBoolean
    xmlXPathObjectPtr	xmlXPathNewBoolean	(int val)
Create a new xmlXPathObjectPtr of type boolean and of value @val
`val`: | the boolean value
`Returns`: | the newly created object.
### Function: xmlXPathNewCString
    xmlXPathObjectPtr	xmlXPathNewCString	(const char * val)
Create a new xmlXPathObjectPtr of type string and of value @val
`val`: | the char * value
`Returns`: | the newly created object.
### Function: xmlXPathNewFloat
    xmlXPathObjectPtr	xmlXPathNewFloat	(double val)
Create a new xmlXPathObjectPtr of type double and of value @val
`val`: | the double value
`Returns`: | the newly created object.
### Function: xmlXPathNewNodeSet
    xmlXPathObjectPtr	xmlXPathNewNodeSet	(xmlNodePtr val)
Create a new xmlXPathObjectPtr of type NodeSet and initialize it with the single Node @val
`val`: | the NodePtr value
`Returns`: | the newly created object.
### Function: xmlXPathNewNodeSetList
    xmlXPathObjectPtr	xmlXPathNewNodeSetList	(xmlNodeSetPtr val)
Create a new xmlXPathObjectPtr of type NodeSet and initialize it with the Nodeset @val
`val`: | an existing NodeSet
`Returns`: | the newly created object.
### Function: xmlXPathNewParserContext
    xmlXPathParserContextPtr	xmlXPathNewParserContext	(const xmlChar * str,
    							 xmlXPathContextPtr ctxt)
Create a new xmlXPathParserContext
`str`: | the XPath expression
`ctxt`: | the XPath context
`Returns`: | the xmlXPathParserContext just allocated.
### Function: xmlXPathNewString
    xmlXPathObjectPtr	xmlXPathNewString	(const xmlChar * val)
Create a new xmlXPathObjectPtr of type string and of value @val
`val`: | the xmlChar * value
`Returns`: | the newly created object.
### Function: xmlXPathNewValueTree
    xmlXPathObjectPtr	xmlXPathNewValueTree	(xmlNodePtr val)
Create a new xmlXPathObjectPtr of type Value Tree (XSLT) and initialize it with the tree root @val
`val`: | the NodePtr value
`Returns`: | the newly created object.
### Function: xmlXPathNextAncestor
    xmlNodePtr	xmlXPathNextAncestor	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "ancestor" direction the ancestor axis contains the ancestors of the context node; the ancestors of the context node consist of the parent of context node and the parent's parent and so on; the nodes are ordered in reverse document order; thus the parent is the first node on the axis, and the parent's parent is the second node on the axis
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextAncestorOrSelf
    xmlNodePtr	xmlXPathNextAncestorOrSelf	(xmlXPathParserContextPtr ctxt,
    						 xmlNodePtr cur)
Traversal function for the "ancestor-or-self" direction he ancestor-or-self axis contains the context node and ancestors of the context node in reverse document order; thus the context node is the first node on the axis, and the context node's parent the second; parent here is defined the same as with the parent axis.
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextAttribute
    xmlNodePtr	xmlXPathNextAttribute	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "attribute" direction TODO: support DTD inherited default attributes
`ctxt`: | the XPath Parser context
`cur`: | the current attribute in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextChild
    xmlNodePtr	xmlXPathNextChild	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "child" direction The child axis contains the children of the context node in document order.
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextDescendant
    xmlNodePtr	xmlXPathNextDescendant	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "descendant" direction the descendant axis contains the descendants of the context node in document order; a descendant is a child or a child of a child and so on.
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextDescendantOrSelf
    xmlNodePtr	xmlXPathNextDescendantOrSelf	(xmlXPathParserContextPtr ctxt,
    						 xmlNodePtr cur)
Traversal function for the "descendant-or-self" direction the descendant-or-self axis contains the context node and the descendants of the context node in document order; thus the context node is the first node on the axis, and the first child of the context node is the second node on the axis
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextFollowing
    xmlNodePtr	xmlXPathNextFollowing	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "following" direction The following axis contains all nodes in the same document as the context node that are after the context node in document order, excluding any descendants and excluding attribute nodes and namespace nodes; the nodes are ordered in document order
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextFollowingSibling
    xmlNodePtr	xmlXPathNextFollowingSibling	(xmlXPathParserContextPtr ctxt,
    						 xmlNodePtr cur)
Traversal function for the "following-sibling" direction The following-sibling axis contains the following siblings of the context node in document order.
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextNamespace
    xmlNodePtr	xmlXPathNextNamespace	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "namespace" direction the namespace axis contains the namespace nodes of the context node; the order of nodes on this axis is implementation-defined; the axis will be empty unless the context node is an element We keep the XML namespace node at the end of the list.
`ctxt`: | the XPath Parser context
`cur`: | the current attribute in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextParent
    xmlNodePtr	xmlXPathNextParent	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "parent" direction The parent axis contains the parent of the context node, if there is one.
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextPreceding
    xmlNodePtr	xmlXPathNextPreceding	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "preceding" direction the preceding axis contains all nodes in the same document as the context node that are before the context node in document order, excluding any ancestors and excluding attribute nodes and namespace nodes; the nodes are ordered in reverse document order
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextPrecedingSibling
    xmlNodePtr	xmlXPathNextPrecedingSibling	(xmlXPathParserContextPtr ctxt,
    						 xmlNodePtr cur)
Traversal function for the "preceding-sibling" direction The preceding-sibling axis contains the preceding siblings of the context node in reverse document order; the first preceding sibling is first on the axis; the sibling preceding that node is the second on the axis and so on.
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNextSelf
    xmlNodePtr	xmlXPathNextSelf	(xmlXPathParserContextPtr ctxt,
    					 xmlNodePtr cur)
Traversal function for the "self" direction The self axis contains just the context node itself
`ctxt`: | the XPath Parser context
`cur`: | the current node in the traversal
`Returns`: | the next element following that axis
### Function: xmlXPathNodeLeading
    xmlNodeSetPtr	xmlXPathNodeLeading	(xmlNodeSetPtr nodes,
    					 xmlNodePtr node)
Implements the EXSLT - Sets leading() function: node-set set:leading (node-set, node-set) @nodes is sorted by document order, then #exslSetsNodeLeadingSorted is called.
`nodes`: | a node-set
`node`: | a node
`Returns`: | the nodes in @nodes that precede @node in document order, @nodes if @node is NULL or an empty node-set if @nodes doesn't contain @node
### Function: xmlXPathNodeLeadingSorted
    xmlNodeSetPtr	xmlXPathNodeLeadingSorted	(xmlNodeSetPtr nodes,
    						 xmlNodePtr node)
Implements the EXSLT - Sets leading() function: node-set set:leading (node-set, node-set)
`nodes`: | a node-set, sorted by document order
`node`: | a node
`Returns`: | the nodes in @nodes that precede @node in document order, @nodes if @node is NULL or an empty node-set if @nodes doesn't contain @node
### Function: xmlXPathNodeSetAdd
    int	xmlXPathNodeSetAdd		(xmlNodeSetPtr cur,
    					 xmlNodePtr val)
add a new xmlNodePtr to an existing NodeSet
`cur`: | the initial node set
`val`: | a new xmlNodePtr
`Returns`: | 0 in case of success, and -1 in case of error
### Function: xmlXPathNodeSetAddNs
    int	xmlXPathNodeSetAddNs		(xmlNodeSetPtr cur,
    					 xmlNodePtr node,
    					 xmlNsPtr ns)
add a new namespace node to an existing NodeSet
`cur`: | the initial node set
`node`: | the hosting node
`ns`: | a the namespace node
`Returns`: | 0 in case of success and -1 in case of error
### Function: xmlXPathNodeSetAddUnique
    int	xmlXPathNodeSetAddUnique	(xmlNodeSetPtr cur,
    					 xmlNodePtr val)
add a new xmlNodePtr to an existing NodeSet, optimized version when we are sure the node is not already in the set.
`cur`: | the initial node set
`val`: | a new xmlNodePtr
`Returns`: | 0 in case of success and -1 in case of failure
### Function: xmlXPathNodeSetContains
    int	xmlXPathNodeSetContains		(xmlNodeSetPtr cur,
    					 xmlNodePtr val)
checks whether @cur contains @val
`cur`: | the node-set
`val`: | the node
`Returns`: | true (1) if @cur contains @val, false (0) otherwise
### Function: xmlXPathNodeSetDel
    void	xmlXPathNodeSetDel		(xmlNodeSetPtr cur,
    					 xmlNodePtr val)
Removes an xmlNodePtr from an existing NodeSet
`cur`: | the initial node set
`val`: | an xmlNodePtr
### Function: xmlXPathNodeSetFreeNs
    void	xmlXPathNodeSetFreeNs		(xmlNsPtr ns)
Namespace nodes in libxml don't match the XPath semantic. In a node set the namespace nodes are duplicated and the next pointer is set to the parent node in the XPath semantic. Check if such a node needs to be freed
`ns`: | the XPath namespace node found in a nodeset.
### Function: xmlXPathNodeSetMerge
    xmlNodeSetPtr	xmlXPathNodeSetMerge	(xmlNodeSetPtr val1,
    					 xmlNodeSetPtr val2)
Merges two nodesets, all nodes from @val2 are added to @val1 if @val1 is NULL, a new set is created and copied from @val2
`val1`: | the first NodeSet or NULL
`val2`: | the second NodeSet
`Returns`: | @val1 once extended or NULL in case of error.
### Function: xmlXPathNodeSetRemove
    void	xmlXPathNodeSetRemove		(xmlNodeSetPtr cur,
    					 int val)
Removes an entry from an existing NodeSet list.
`cur`: | the initial node set
`val`: | the index to remove
### Function: xmlXPathNodeSetSort
    void	xmlXPathNodeSetSort		(xmlNodeSetPtr set)
Sort the node set in document order
`set`: | the node set
### Function: xmlXPathNodeTrailing
    xmlNodeSetPtr	xmlXPathNodeTrailing	(xmlNodeSetPtr nodes,
    					 xmlNodePtr node)
Implements the EXSLT - Sets trailing() function: node-set set:trailing (node-set, node-set) @nodes is sorted by document order, then #xmlXPathNodeTrailingSorted is called.
`nodes`: | a node-set
`node`: | a node
`Returns`: | the nodes in @nodes that follow @node in document order, @nodes if @node is NULL or an empty node-set if @nodes doesn't contain @node
### Function: xmlXPathNodeTrailingSorted
    xmlNodeSetPtr	xmlXPathNodeTrailingSorted	(xmlNodeSetPtr nodes,
    						 xmlNodePtr node)
Implements the EXSLT - Sets trailing() function: node-set set:trailing (node-set, node-set)
`nodes`: | a node-set, sorted by document order
`node`: | a node
`Returns`: | the nodes in @nodes that follow @node in document order, @nodes if @node is NULL or an empty node-set if @nodes doesn't contain @node
### Function: xmlXPathNormalizeFunction
    void	xmlXPathNormalizeFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the normalize-space() XPath function string normalize-space(string?) The normalize-space function returns the argument string with white space normalized by stripping leading and trailing whitespace and replacing sequences of whitespace characters by a single space. Whitespace characters are the same allowed by the S production in XML. If the argument is omitted, it defaults to the context node converted to a string, in other words the value of the context node.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathNotEqualValues
    int	xmlXPathNotEqualValues		(xmlXPathParserContextPtr ctxt)
Implement the equal operation on XPath objects content: @arg1 == @arg2
`ctxt`: | the XPath Parser context
`Returns`: | 0 or 1 depending on the results of the test.
### Function: xmlXPathNotFunction
    void	xmlXPathNotFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the not() XPath function boolean not(boolean) The not function returns true if its argument is false, and false otherwise.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathNsLookup
    const xmlChar *	xmlXPathNsLookup	(xmlXPathContextPtr ctxt,
    					 const xmlChar * prefix)
Search in the namespace declaration array of the context for the given namespace name associated to the given prefix
`ctxt`: | the XPath context
`prefix`: | the namespace prefix value
`Returns`: | the value or NULL if not found
### Function: xmlXPathNumberFunction
    void	xmlXPathNumberFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the number() XPath function number number(object?)
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathParseNCName
    xmlChar *	xmlXPathParseNCName	(xmlXPathParserContextPtr ctxt)
parse an XML namespace non qualified name. [NS 3] NCName ::= (Letter | '_') (NCNameChar)* [NS 4] NCNameChar ::= Letter | Digit | '.' | '-' | '_' | CombiningChar | Extender
`ctxt`: | the XPath Parser context
`Returns`: | the namespace name or NULL
### Function: xmlXPathParseName
    xmlChar *	xmlXPathParseName	(xmlXPathParserContextPtr ctxt)
parse an XML name [4] NameChar ::= Letter | Digit | '.' | '-' | '_' | ':' | CombiningChar | Extender [5] Name ::= (Letter | '_' | ':') (NameChar)*
`ctxt`: | the XPath Parser context
`Returns`: | the namespace name or NULL
### Function: xmlXPathPopBoolean
    int	xmlXPathPopBoolean		(xmlXPathParserContextPtr ctxt)
Pops a boolean from the stack, handling conversion if needed. Check error with #xmlXPathCheckError.
`ctxt`: | an XPath parser context
`Returns`: | the boolean
### Function: xmlXPathPopExternal
    void *	xmlXPathPopExternal		(xmlXPathParserContextPtr ctxt)
Pops an external object from the stack, handling conversion if needed. Check error with #xmlXPathCheckError.
`ctxt`: | an XPath parser context
`Returns`: | the object
### Function: xmlXPathPopNodeSet
    xmlNodeSetPtr	xmlXPathPopNodeSet	(xmlXPathParserContextPtr ctxt)
Pops a node-set from the stack, handling conversion if needed. Check error with #xmlXPathCheckError.
`ctxt`: | an XPath parser context
`Returns`: | the node-set
### Function: xmlXPathPopNumber
    double	xmlXPathPopNumber		(xmlXPathParserContextPtr ctxt)
Pops a number from the stack, handling conversion if needed. Check error with #xmlXPathCheckError.
`ctxt`: | an XPath parser context
`Returns`: | the number
### Function: xmlXPathPopString
    xmlChar *	xmlXPathPopString	(xmlXPathParserContextPtr ctxt)
Pops a string from the stack, handling conversion if needed. Check error with #xmlXPathCheckError.
`ctxt`: | an XPath parser context
`Returns`: | the string
### Function: xmlXPathPositionFunction
    void	xmlXPathPositionFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the position() XPath function number position() The position function returns the position of the context node in the context node list. The first position is 1, and so the last position will be equal to last().
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathRegisterAllFunctions
    void	xmlXPathRegisterAllFunctions	(xmlXPathContextPtr ctxt)
Registers all default XPath functions in this context
`ctxt`: | the XPath context
### Function: xmlXPathRegisterFunc
    int	xmlXPathRegisterFunc		(xmlXPathContextPtr ctxt,
    					 const xmlChar * name,
    					 xmlXPathFunction f)
Register a new function. If @f is NULL it unregisters the function
`ctxt`: | the XPath context
`name`: | the function name
`f`: | the function implementation or NULL
`Returns`: | 0 in case of success, -1 in case of error
### Function: xmlXPathRegisterFuncLookup
    void	xmlXPathRegisterFuncLookup	(xmlXPathContextPtr ctxt,
    					 xmlXPathFuncLookupFunc f,
    					 void * funcCtxt)
Registers an external mechanism to do function lookup.
`ctxt`: | the XPath context
`f`: | the lookup function
`funcCtxt`: | the lookup data
### Function: xmlXPathRegisterFuncNS
    int	xmlXPathRegisterFuncNS		(xmlXPathContextPtr ctxt,
    					 const xmlChar * name,
    					 const xmlChar * ns_uri,
    					 xmlXPathFunction f)
Register a new function. If @f is NULL it unregisters the function
`ctxt`: | the XPath context
`name`: | the function name
`ns_uri`: | the function namespace URI
`f`: | the function implementation or NULL
`Returns`: | 0 in case of success, -1 in case of error
### Function: xmlXPathRegisterNs
    int	xmlXPathRegisterNs		(xmlXPathContextPtr ctxt,
    					 const xmlChar * prefix,
    					 const xmlChar * ns_uri)
Register a new namespace. If @ns_uri is NULL it unregisters the namespace
`ctxt`: | the XPath context
`prefix`: | the namespace prefix cannot be NULL or empty string
`ns_uri`: | the namespace name
`Returns`: | 0 in case of success, -1 in case of error
### Function: xmlXPathRegisterVariable
    int	xmlXPathRegisterVariable	(xmlXPathContextPtr ctxt,
    					 const xmlChar * name,
    					 xmlXPathObjectPtr value)
Register a new variable value. If @value is NULL it unregisters the variable
`ctxt`: | the XPath context
`name`: | the variable name
`value`: | the variable value or NULL
`Returns`: | 0 in case of success, -1 in case of error
### Function: xmlXPathRegisterVariableLookup
    void	xmlXPathRegisterVariableLookup	(xmlXPathContextPtr ctxt,
    					 xmlXPathVariableLookupFunc f,
    					 void * data)
register an external mechanism to do variable lookup
`ctxt`: | the XPath context
`f`: | the lookup function
`data`: | the lookup data
### Function: xmlXPathRegisterVariableNS
    int	xmlXPathRegisterVariableNS	(xmlXPathContextPtr ctxt,
    					 const xmlChar * name,
    					 const xmlChar * ns_uri,
    					 xmlXPathObjectPtr value)
Register a new variable value. If @value is NULL it unregisters the variable
`ctxt`: | the XPath context
`name`: | the variable name
`ns_uri`: | the variable namespace URI
`value`: | the variable value or NULL
`Returns`: | 0 in case of success, -1 in case of error
### Function: xmlXPathRegisteredFuncsCleanup
    void	xmlXPathRegisteredFuncsCleanup	(xmlXPathContextPtr ctxt)
Cleanup the XPath context data associated to registered functions
`ctxt`: | the XPath context
### Function: xmlXPathRegisteredNsCleanup
    void	xmlXPathRegisteredNsCleanup	(xmlXPathContextPtr ctxt)
Cleanup the XPath context data associated to registered variables
`ctxt`: | the XPath context
### Function: xmlXPathRegisteredVariablesCleanup
    void	xmlXPathRegisteredVariablesCleanup	(xmlXPathContextPtr ctxt)
Cleanup the XPath context data associated to registered variables
`ctxt`: | the XPath context
### Function: xmlXPathRoot
    void	xmlXPathRoot			(xmlXPathParserContextPtr ctxt)
Initialize the context to the root of the document
`ctxt`: | the XPath Parser context
### Function: xmlXPathRoundFunction
    void	xmlXPathRoundFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the round() XPath function number round(number) The round function returns the number that is closest to the argument and that is an integer. If there are two such numbers, then the one that is even is returned.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathStartsWithFunction
    void	xmlXPathStartsWithFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the starts-with() XPath function boolean starts-with(string, string) The starts-with function returns true if the first argument string starts with the second argument string, and otherwise returns false.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathStringEvalNumber
    double	xmlXPathStringEvalNumber	(const xmlChar * str)
[30a] Float ::= Number ('e' Digits?)? [30] Number ::= Digits ('.' Digits?)? | '.' Digits [31] Digits ::= [0-9]+ Compile a Number in the string In complement of the Number expression, this function also handles negative values : '-' Number.
`str`: | A string to scan
`Returns`: | the double value.
### Function: xmlXPathStringFunction
    void	xmlXPathStringFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the string() XPath function string string(object?) The string function converts an object to a string as follows: - A node-set is converted to a string by returning the value of the node in the node-set that is first in document order. If the node-set is empty, an empty string is returned. - A number is converted to a string as follows + NaN is converted to the string NaN + positive zero is converted to the string 0 + negative zero is converted to the string 0 + positive infinity is converted to the string Infinity + negative infinity is converted to the string -Infinity + if the number is an integer, the number is represented in decimal form as a Number with no decimal point and no leading zeros, preceded by a minus sign (-) if the number is negative + otherwise, the number is represented in decimal form as a Number including a decimal point with at least one digit before the decimal point and at least one digit after the decimal point, preceded by a minus sign (-) if the number is negative; there must be no leading zeros before the decimal point apart possibly from the one required digit immediately before the decimal point; beyond the one required digit after the decimal point there must be as many, but only as many, more digits as are needed to uniquely distinguish the number from all other IEEE 754 numeric values. - The boolean false value is converted to the string false. The boolean true value is converted to the string true. If the argument is omitted, it defaults to a node-set with the context node as its only member.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathStringLengthFunction
    void	xmlXPathStringLengthFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the string-length() XPath function number string-length(string?) The string-length returns the number of characters in the string (see [3.6 Strings]). If the argument is omitted, it defaults to the context node converted to a string, in other words the value of the context node.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathSubValues
    void	xmlXPathSubValues		(xmlXPathParserContextPtr ctxt)
Implement the subtraction operation on XPath objects: The numeric operators convert their operands to numbers as if by calling the number function.
`ctxt`: | the XPath Parser context
### Function: xmlXPathSubstringAfterFunction
    void	xmlXPathSubstringAfterFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the substring-after() XPath function string substring-after(string, string) The substring-after function returns the substring of the first argument string that follows the first occurrence of the second argument string in the first argument string, or the empty stringi if the first argument string does not contain the second argument string. For example, substring-after("1999/04/01","/") returns 04/01, and substring-after("1999/04/01","19") returns 99/04/01.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathSubstringBeforeFunction
    void	xmlXPathSubstringBeforeFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the substring-before() XPath function string substring-before(string, string) The substring-before function returns the substring of the first argument string that precedes the first occurrence of the second argument string in the first argument string, or the empty string if the first argument string does not contain the second argument string. For example, substring-before("1999/04/01","/") returns 1999.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathSubstringFunction
    void	xmlXPathSubstringFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the substring() XPath function string substring(string, number, number?) The substring function returns the substring of the first argument starting at the position specified in the second argument with length specified in the third argument. For example, substring("12345",2,3) returns "234". If the third argument is not specified, it returns the substring starting at the position specified in the second argument and continuing to the end of the string. For example, substring("12345",2) returns "2345". More precisely, each character in the string (see [3.6 Strings]) is considered to have a numeric position: the position of the first character is 1, the position of the second character is 2 and so on. The returned substring contains those characters for which the position of the character is greater than or equal to the second argument and, if the third argument is specified, less than the sum of the second and third arguments; the comparisons and addition used for the above follow the standard IEEE 754 rules. Thus: - substring("12345", 1.5, 2.6) returns "234" - substring("12345", 0, 3) returns "12" - substring("12345", 0 div 0, 3) returns "" - substring("12345", 1, 0 div 0) returns "" - substring("12345", -42, 1 div 0) returns "12345" - substring("12345", -1 div 0, 1 div 0) returns ""
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathSumFunction
    void	xmlXPathSumFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the sum() XPath function number sum(node-set) The sum function returns the sum of the values of the nodes in the argument node-set.
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathTrailing
    xmlNodeSetPtr	xmlXPathTrailing	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
Implements the EXSLT - Sets trailing() function: node-set set:trailing (node-set, node-set) @nodes1 and @nodes2 are sorted by document order, then #xmlXPathTrailingSorted is called.
`nodes1`: | a node-set
`nodes2`: | a node-set
`Returns`: | the nodes in @nodes1 that follow the first node in @nodes2 in document order, @nodes1 if @nodes2 is NULL or empty or an empty node-set if @nodes1 doesn't contain @nodes2
### Function: xmlXPathTrailingSorted
    xmlNodeSetPtr	xmlXPathTrailingSorted	(xmlNodeSetPtr nodes1,
    					 xmlNodeSetPtr nodes2)
Implements the EXSLT - Sets trailing() function: node-set set:trailing (node-set, node-set)
`nodes1`: | a node-set, sorted by document order
`nodes2`: | a node-set, sorted by document order
`Returns`: | the nodes in @nodes1 that follow the first node in @nodes2 in document order, @nodes1 if @nodes2 is NULL or empty or an empty node-set if @nodes1 doesn't contain @nodes2
### Function: xmlXPathTranslateFunction
    void	xmlXPathTranslateFunction	(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the translate() XPath function string translate(string, string, string) The translate function returns the first argument string with occurrences of characters in the second argument string replaced by the character at the corresponding position in the third argument string. For example, translate("bar","abc","ABC") returns the string BAr. If there is a character in the second argument string with no character at a corresponding position in the third argument string (because the second argument string is longer than the third argument string), then occurrences of that character in the first argument string are removed. For example, translate("--aaa--","abc-","ABC")
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathTrueFunction
    void	xmlXPathTrueFunction		(xmlXPathParserContextPtr ctxt,
    					 int nargs)
Implement the true() XPath function boolean true()
`ctxt`: | the XPath Parser context
`nargs`: | the number of arguments
### Function: xmlXPathValueFlipSign
    void	xmlXPathValueFlipSign		(xmlXPathParserContextPtr ctxt)
Implement the unary - operation on an XPath object The numeric operators convert their operands to numbers as if by calling the number function.
`ctxt`: | the XPath Parser context
### Function: xmlXPathVariableLookup
    xmlXPathObjectPtr	xmlXPathVariableLookup	(xmlXPathContextPtr ctxt,
    						 const xmlChar * name)
Search in the Variable array of the context for the given variable value.
`ctxt`: | the XPath context
`name`: | the variable name
`Returns`: | a copy of the value or NULL if not found
### Function: xmlXPathVariableLookupNS
    xmlXPathObjectPtr	xmlXPathVariableLookupNS	(xmlXPathContextPtr ctxt,
    							 const xmlChar * name,
    							 const xmlChar * ns_uri)
Search in the Variable array of the context for the given variable value.
`ctxt`: | the XPath context
`name`: | the variable name
`ns_uri`: | the variable namespace URI
`Returns`: | the a copy of the value or NULL if not found
### Function: xmlXPathWrapCString
    xmlXPathObjectPtr	xmlXPathWrapCString	(char * val)
Wraps a string into an XPath object.
`val`: | the char * value
`Returns`: | the newly created object.
### Function: xmlXPathWrapExternal
    xmlXPathObjectPtr	xmlXPathWrapExternal	(void * val)
Wraps the @val data into an XPath object.
`val`: | the user data
`Returns`: | the newly created object.
### Function: xmlXPathWrapNodeSet
    xmlXPathObjectPtr	xmlXPathWrapNodeSet	(xmlNodeSetPtr val)
Wrap the Nodeset @val in a new xmlXPathObjectPtr
`val`: | the NodePtr value
`Returns`: | the newly created object.
### Function: xmlXPathWrapString
    xmlXPathObjectPtr	xmlXPathWrapString	(xmlChar * val)
Wraps the @val string into an XPath object.
`val`: | the xmlChar * value
`Returns`: | the newly created object.
### Function: xmlXPatherror
    void	xmlXPatherror			(xmlXPathParserContextPtr ctxt,
    					 const char * file,
    					 int line,
    					 int no)
Formats an error message.
`ctxt`: | the XPath Parser context
`file`: | the file name
`line`: | the line number
`no`: | the error number
Daniel Veillard