A first dozen XPath functions

A first dozen XPath functions Already covered count() Kay 733 not() Functions that operate on strings normalize-space() Kay 845 string-length() replace() Kay 862 translate() Kay 897 concat() functions that operate on sets of numbers avg() Kay 718 max() Kay 830 min() Kay 830 sum() Kay 889 distinct-values() Kay 749 position() and last() Kay 854 current-date() Kay 738

normalize-space() and string-length() Trims leading and trailing whitespace; reduces runs of any remaining space to single blank Example: string-length( //l[@xml:id eq 'sha-ham301055']/text() ) → 70 string-length( normalize-space( //l[@xml:id eq 'sha-ham301055']/text() ) ) → 42 Uses Clean user input

replace() Syntax:

replace(input-string, regex-pattern, replacement-string,
	    flags)

Example: replace('Syd','y','i') Task: Retrieve all roles in Hamlet and replace “a” with “Hi, Mom!” Complication: What’s wrong with

replace(//role,'a','Hi,
	    Mom!')?

Clever trick: Use an path expression with a dot to refer to the context node, e.g., //role/upper-case(.) means “find all the role elements and then upper-case the context node (the role element you just found)” Uses Regex patterns (coming later), such as “transform all dates like MM/DD/YYYY to YYYY-MM-DD” One-to-many or many-to-one transformations (e.g., change LC Cyrillic romanization of “ч” as “ch” into linguistic “č” [or vice versa])

translate() Syntax:

translate(input-string, characters-to-match,
	    replacement-characters)

Limitation: performs only one-for-one replacements (use replace() for more complex replacements) Example: translate('Syd','ABCDEFGHIJKLMNOPQRSTUVWXYZ','abcdefghijklmnopqrstuvwxyz') Cf. upper-case() and lower-case() Task: Replace all vowels (aeiou) in the names of Hamlet characters with exclamation marks Uses One-to-one transformations Change unix paths to Windows paths Change European numerical punctuation to US Convert text from legacy character sets to Unicode

concat() Syntax: concat( str1, str2, str3 ) → str1str2str3 Simple example:

concat('David has ', $npt, '
	    penguin ties')

Complex example:

concat('Syd has ', if ($npt >
	    0) then $npt else 'no', ' penguin tie', if ($npt > 1) then
	    's' else '')

avg(), max(), min(), sum() Syntax: avg( sequence-of-numbers ) Example: avg( (1,2,3,4,5,6) ) What’s wrong with: avg( 1,2,3,4,5,6 )? Similarly: max(), min(), and sum() Uses Basic arithmetic operations on sets of numerical data items Task: Find the average length of a speech in Hamlet, and then the longest and shortest lengths Hints The function string-length(string) returns the length of the string The dot (.) refers to the current item //sp/string-length(.) will return a sequence consisting of the length of each string (try it)

distinct-values(): Roles in (ham.xml) distinct-values(//speaker) Returns 38 items What does //speaker return? //role Returns 37 items What does distinct-values(//role) return? Food for thought: What does the discrepancy between speakers and roles mean?

position() and last() Returns the position of an item in a sequence Syntax: item/position() Example: //role/position() returns the number of each role in the list of roles Task: find the stage direction in the last line Hamlet speaks Note: the last() function returns the sequence number of the last node in the set

current-date() Syntax: current-date() Returns the current date; useful for date-stamping Cf. current-dateTime(), current-time() May be used with format-date() (-dateTime, -time) to massage output Kay 781 format-date() works only in XSLT, not in the XPath browser of <oXygen/> Example: current-date() Example: open and run djb_calendar.xsl in the <oXygen/> XSLT debugger (use any XML file as the source)