Is there an "if -then - else " statement in XPath?

Question

It seems with all the rich amount of function in xpath that you could do an "if" . However , my engine keeps insisting "there is no such function" , and I hardly find any documentation on the web (I found some dubious sources , but the syntax they had didn't work)

I need to remove ':' from the end of a string (if exist), so I wanted to do this:

if (fn:ends-with(//div [@id='head']/text(),': '))             then (fn:substring-before(//div [@id='head']/text(),': ') )             else (//div [@id='head']/text()) 

Any advice?

Answer 1

Yes, there is a way to do it in XPath 1.0:

 concat(   substring($s1, 1, number($condition)      * string-length($s1)),   substring($s2, 1, number(not($condition)) * string-length($s2)) ) 

This relies on the concatenation of two mutually exclusive strings, the first one being empty if the condition is false (0 * string-length(...)), the second one being empty if the condition is true. This is called "Becker's method", attributed to Oliver Becker (original link is now dead, the web archive has a copy).

In your case:

 concat(   substring(     substring-before(//div[@id='head']/text(), ': '),     1,      number(       ends-with(//div[@id='head']/text(), ': ')     )     * string-length(substring-before(//div [@id='head']/text(), ': '))   ),   substring(     //div[@id='head']/text(),      1,      number(not(       ends-with(//div[@id='head']/text(), ': ')     ))     * string-length(//div[@id='head']/text())   ) ) 

Though I would try to get rid of all the "//" before.

Also, there is the possibility that //div[@id='head'] returns more than one node.
Just be aware of that — using //div[@id='head'][1] is more defensive.