[antlr-interest] passing an argument to a lexer

[siemsen at ucar.edu]

Thanks, Gavin and Johannes.  The cast helped.  My lexer error messages  
now contain the current file name.  Very nice!

-- Pete


On Apr 26, 2008, at 4:33 AM, Gavin Lambert wrote:

> At 19:23 26/04/2008, siemsen at ucar.edu wrote:
>> I hoped that calling input.getSourceName() from the relevant lexer  
>> rule action might give the full path to the file, but the compiler  
>> gave me
>>
>> /Users/siemsen/TranslateCIM/target/generated-sources/antlr/ 
>> TranslateCIMLexer.java:[1449,82] cannot find symbol
>> symbol  : method getSourceName()
>> location: interface org.antlr.runtime.CharStream
>
> getSourceName isn't defined on CharStream, it's on ANTLRFileStream.   
> You can get to it with a cast, if you're absolutely certain you're  
> only going to be giving file streams to the lexer:
>
> ... ((ANTLRFileStream)input).getSourceName() ...
>
> (Actually, it appears to be *defined* on ANTLRStringStream, but I  
> can't see how this would give it a useful value.)
>
> Another (possibly better) option is to use a @members (or  
> @lexer::members) section to create an additional field/property in  
> your lexer class where you can store the base directory name.  This  
> is potentially more flexible, since you can extend it later to  
> search multiple folders (for example).  It also doesn't limit you to  
> using file streams, which is useful when unit-testing the grammar.
>