4.1. Introduction to Functions4.1.1. What Functions Do4.1.2. Functions Within Functions4.2. XPath Function Types4.2.1. Node-Set Functions4.2.1.1. last( )4.2.1.2. position( )4.2.1.3. count(nodeset)4.2.1.4. id(anytype)4.2.1.5. id( ) and node-set arguments4.2.1.6. local-name(nodeset?)4.2.1.7. namespace-uri(nodeset?)4.2.1.8. name(nodeset?)4.2.2. String Functions4.2.2.1. string(anytype?)4.2.2.2. concat(string1, string2, ...)4.2.2.3. starts-with(string1, string2)4.2.2.4. contains(string1, string2)4.2.2.5. substring(string, number1, number2?)4.2.2.6. substring-before(string1, string2) and substring-after(string1, string2)4.2.2.7. string-length(string?)4.2.2.8. normalize-space(string?)4.2.2.9. translate(string1, string2, string3)4.2.3. Boolean Functions4.2.3.1. boolean(anytype)4.2.3.2. not(boolean)4.2.3.3. true() and false( )4.2.3.4. lang(string)4.2.4. Numeric Functions4.2.4.1. number(anytype?)4.2.4.2. sum(nodeset)4.2.4.3. floor(number) and ceiling(number)4.2.4.4. round(number)4.3. XPath Numeric Operators4.3.1. div4.3.2. mod