Re: A syntax highlighting trivia: matching operators

On 20/02/2018 16:10, Charles E Campbell wrote:
> Lifepillar wrote:
>> Suppose that @, @@, and @@@ are three operators and that @ is not in
>> iskeyword. Besides, the operators may not necessarily be surrounded
>> by spaces or alphanumeric characters: for example, one may encounter
>> @( at the begin of the line (as in this line).
>>
>> How would you define syntax rules to highlight those three operators,
>> but not @@@@, @@@@@, and so on?
>>
>> The above is an instance of a problem I have encountered in my
>> PostgreSQL syntax plugin. Currently, I have rules like these:
>>
>> syn match sqlIsOperator "[!?~#^@<=>%&|*/+-]\+" contains=sqlOperator
>> syn match sqlOperator contained "@@@\|@@\|@"
>> etc...
>>
>> but those do not limit the highlighted sequences to just those defined
>> by the sqlOperator rules. More precisely, @@@@ is entirely highlighted
>> because its @@@ prefix matches and the last @ matches, too.
> Hello:
>
> Please try the attached at.vim file. I've included a "junk" file for
> illustration.

Nice! I think that the first syntax rule should include \ze, though:

syn match OneAt '@\{1,3}\ze\([^@]\|$\)'

And, correct me if I am wrong, the rules can be further simplified to:

syn match OneAt '@\{1,3}'
syn match LotsaAt '@\{4,}'

hi default link OneAt Operator

I hadn't thought of using a rule without a corresponding highlighting
to catch "negative" matches. Clever trick!

Thanks!
Life.

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