[antlr-interest] Global scopes for lexers

[Terence Parr]

On Jul 31, 2007, at 8:51 AM, Alex Shneyderman wrote:

>> It's unsupported.  May i ask why you want them?
>> Ter
>
> I have a language where new lines can be significant or not depending
> on the type of curlies they are in. So, if say we are in {} new lines
> are significant but if we are in () or [] they are ignored.
>
> Currently, v2 grammar keeps a stack in lexer to keep track of this.
> Every time there is { the levelNumber is pushed onto the stack and
> levelNumber member var of lexer is set to 0. If } is read we pop the
> stack and assign the value popped to the levelNumber instance member
> of the lexer. If we see [ or ( we increment levelNumber; seeing ) or ]
> we decrement the levelNumber.
>
> Now if we see a new line and levelNumber != 0 then we skip the new
> line otherwise we emit a NL (as it is significant) token.

can you get away with just a simple counter for level overall, one  
for each kind of nesting?

> Comparing the code generated for parser's global scope it is
> practically identical to what the hackish stack solution looks like
> with v2 grammar.

Interesting...well, the stack was not meant to work across lexer  
nextToken calls, only nested function calls.  The dyn scoping here is  
for nesting not for stacks across method calls.

Ter