[TxMt] match and look ahead?

[Gerd Knops]

On Mon, Sep 5, at 3:16 PM, Allan Odgaard wrote:

> On 05/09/2005, at 21.26, Gerd Knops wrote:
>
>
>> To make it easier to visually parse blocks, I am trying to write a  
>> pattern that matches on 'even tabs' and give them a light gray  
>> background.
>>
>> I tried something like
>>     match= "^(?=\\t)\\t";
>> but that doesn't seem to work. Is look ahead not possible in  
>> pattern matches?
>>
>
> It is, but that pattern would match the first tab on a line.
>
> To markup leading odd/even tabs, you could use a rule like this:
>
>     {   name = "meta.leading-tabs";
>         begin = "^(?=\\t)"; end = "(?=[^\\t])";
>         patterns = (
>             {   match = "(\\t)(\\t)?";
>                 captures = {
>                     1 = { name = "meta.odd-tab"; };
>                     2 = { name = "meta.even-tab"; };
>                 };
>             }
>         );
>     },
>
Fantastic! Works great and makes complex code much more readable. I  
use a 95% white background for the even tabs. It is subtle but  
extremely helpful. May I recommend that being added to all languages  
where it makes sense?

Gerd