Advanced XPath: Using XPath Functions

XPath Functions

Conversion: boolean, string, number
Contexts: deep-equal, last, position
DateTimes: current-dateTime, day-from-dateTime, months-from-duration, timezone-from-dateTime
Math: avg, ceiling, count, floor, max, min, round, sum
Logic: true, false, not
Nodes: lang, local-name, name, namespace-uri, text
Sequences: distinct-values, empty, index-of, subsequence
Strings: concat, contains, lower-case, matches, normalize-space, replace, starts-with, string-length, substring, substring-after, substring-before, tokenize, translate, upper-case

XPath contains numerous functions. Some of the ones I use most include:

Yes! There are more than this!

Conversion Functions

boolean(arg): returns true or false after evaluating the argument
//div[boolean(@n='2')]

string(arg): returns the string value of the argument
//div[string(@n)='2']
number(arg): returns the numerical value of the argument
//div[number(@n)=2]

Conversion functions items and turn them into something else.

Context Functions

deep-equal(param1,param2): returns true if param1 and param2 are fully equal at depth
deep-equal(person, //person[@xml:id='abc'])

last(): returns the number of items in a nodeset thus providing the last one
//div/sp[last()]
position(): returns index position of current node
//div[position()=3]

Context functions tell you something about your context in the document

DateTime Functions

dateTime(date,time): Converts the arguments to a datetime
year-from-dateTime(datetime) Returns an integer that represents the year
- month-from-dateTime(datetime)
- day-from-dateTime(datetime)
- hours-from-dateTime(datetime)
- minutes-from-dateTime(datetime)
- seconds-from-dateTime(datetime)

DateTime functions enable you to manipulate dates

//date[month-from-dateTime(@when)='02']

Duration Functions

years-from-duration(datetimedur) Returns an integer that represents the years component
- months-from-duration(datetimedur)
- days-from-duration(datetimedur)
- hours-from-duration(datetimedur)
- minutes-from-duration(datetimedur)
- seconds-from-duration(datetimedur)

Duration functions enable you to work with time as a duration

//date[days-from-duration(@dur)=3

Date and Time Functions

year-from-date(date) Returns an integer that represents the year
- month-from-date(date)
- day-from-date(date)
hours-from-time(time) Returns an integer that represents the hours
- minutes-from-time(time)
- seconds-from-time(time)

Date and Time functions enable you to work with dates that are not datetimes

//person[year-from-date(birth/@when)=1985]

Timezone Functions

timezone-from-dateTime(datetime)
- timezone-from-date(date)
- timezone-from-time(time)
adjust-dateTime-to-timezone(datetime,timezone)
- adjust-date-to-timezone(date,timezone)
- adjust-time-to-timezone(time,timezone)

Timezone functions enable you to get timezones from dates, or change dates to timezones

//date[timezone-from-date(@when)='-PT5H']

Numerical Functions

abs(num)
Returns the absolute value of the argument
ceiling(num)
Returns the smallest integer that is greater than the number argument
floor(num)
Returns the largest integer that is not greater than the number argument
round(num)
Rounds the number argument to the nearest integer
round-half-to-even(num)
Rounds the number argument to the nearest even integer

Aggregate Functions

count(item,item,...) Returns the count of nodes
avg(arg,arg,...) Returns the average of the argument values
max(arg,arg,...) Returns the argument that is greater than the others
min(arg,arg,...) Returns the argument that is less than the others
sum(arg,arg,...) Returns the sum of the numeric value of each node in the specified node-set

Logic Functions

not(arg) The argument is first reduced to a boolean value by applying the boolean() function. Returns true if the boolean value is false, and false if the boolean value is true
true() Returns the boolean value true
false() Returns the boolean value false

//div[not(@type='act')]

Node Functions

name() Returns the name of the current or specified node
local-name() Returns the name of the current or specified node without the namespace prefix
namespace-uri() Returns the namespace URI of the current or specified node
lang(lang) Returns true if the language of the current node matches the language of the specified language
root() Returns the root of the tree to which the current node or the specified belongs. This will usually be a document node

//*[local-name()='date']

Sequence Functions

index-of((item,item,...),searchitem) Returns the positions within the sequence of items that are equal to the searchitem argument
remove((item,item,...),position) Returns a new sequence constructed from the value of the item arguments - with the item specified by the position argument removed
empty(item,item,...) Returns true if the value of the arguments IS an empty sequence, otherwise it returns false
exists(item,item,...) Returns true if the value of the arguments IS NOT an empty sequence, otherwise it returns false

index-of ((15, 40, 25, 10), 40) = 2

More Sequence Functions

distinct-values((item,item,...),collation) Returns only distinct (different) values
insert-before((item,item,...),pos,inserts) Returns a new sequence with the value of the inserts argument inserted in the position specified by the pos argument
reverse((item,item,...)) Returns the reversed order of the items specified
subsequence((item,item,...),start,len) Returns a sequence of items from the position specified continuing for length specified. The first item is located at position 1
unordered((item,item,...)) Returns the items in an implementation dependent order

distinct-values(//*/@rend)

String Functions

string(arg) Returns the string value of the argument
codepoints-to-string((int,int,...)) Creates a string from a sequence of the Unicode code points
string-to-codepoints(string) Returns the sequence of the Unicode code points from a string
codepoint-equal(comp1,comp2) Returns true if the value of comp1 is Unicode equal to the value of comp2
compare(comp1,comp2) Returns -1 if comp1 is less than comp2, 0 if comp1 is equal to comp2, or 1 if comp1 is greater than comp2

string(@when)

Substring Functions

substring(string,start,len) Returns the substring from the start position to the specified length. Index of the first character is 1. If length is omitted it returns the substring from the start position to the end
string-length(string) Returns the length of the specified string. If there is no string argument it returns the length of the string value of the current node
substring-before(string1,string2) Returns the start of string1 before string2 occurs in it
substring-after(string1,string2) Returns the remainder of string1 after string2 occurs in it

substring-before(substring-after(@when), '-'), '-')

Translation Functions

normalize-space(string) Removes leading and trailing spaces from the specified string, and replaces all internal sequences of white space with one and returns the result. If there is no string argument it does the same on the current node
upper-case(string) Converts the string argument to upper-case
lower-case(string) Converts the string argument to lower-case
translate(string1,string2,string3) Converts string1 by replacing the characters in string2 with the characters in string3

//div[lower-case(@type='chapter')]

String Testing Functions

contains(string1,string2) Returns true if string1 contains string2, otherwise it returns false
starts-with(string1,string2) Returns true if string1 starts with string2, otherwise it returns false
ends-with(string1,string2) Returns true if string1 ends with string2, otherwise it returns false

//ref[not(starts-with(@target, 'http')]

String Testing Functions

concat(string,string,...) Returns the concatenation of the strings
string-join((string,string,...),sep) Returns a string created by concatenating the string arguments and using the sep argument as the separator
matches(string,pattern) Returns true if the string argument matches the pattern, otherwise, it returns false
replace(string,pattern,replace) Returns a string that is created by replacing the given pattern with the replace argument
tokenize(string,pattern) Returns sequence from a string broken up by the pattern

tokenize(string(@when), '-')

Now let's try some of those out

Advanced XPath: Using XPath Functions

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