Re: [xml-dev] XPath expression which checks that all commas are escaped

[Michael Kay <mike@saxonica.com>]

> On 3 Nov 2017, at 19:22, Dimitre Novatchev <dnovatchev@gmail.com> wrote:
> 
>> not(contains(replace(., '\\,', ''), ','))
> 
> And, of course:
> 
> not(matches(., '[^\\],'))
> 


I don't think that detects an unescaped comma at the start of the string.

Also, Roger didn't state the rule, but I suspect that there must only be one backslash before the comma: if there are two ("\\,") then the comma is not escaped because the "\\" represents a real backslash. In fact the rule is then that the number of backslashes preceding the comma must be an odd number.

There may be a more elegant way, but I'd be inclined to do it by first getting rid of all "\\" sequences:

not(matches(replace(., '\\\\', ''), '^,|[^\\],'))

Michael Kay
Saxonica