Alright thanks for your comprehensive answer! I think I got something to
work with :)
Cheers,
Tom
On Tue, Mar 8, 2011 at 8:09 PM, Stephen Tetley
Hi Tom
Here's how I'd do comment annotation in the Parser:
type Comment = String type Identifier = String
I suspect data carrying tokens need to pair the data and the comment so Happy can treat them as a positional reference e.g. $1
data Token = TK_identifier (Identifier,Comment) | TK_kywd_module Comment | ...
Productions now have to use smart constructors:
module :: { Module } : '%module' mname defs { mkModule $1 $2 $3 }
data Module = Module { mod_comment :: Comment , mod_name :: String , mod_body :: [Def] }
The 'smart' constructor takes the comment before the module delacration, any comment between the module start token and the module name is ignored...
mkModule :: Comment -> (String,Comment) -> [Def] -> Module mkModule outer_comment (mname, _) defs = Module outer_comment mname defs
As for error handling, the strategy is to add error handling productions after "good" productions.
Now module can "handle" a missing module name:
module :: { Module } : '%module' mname defs { mkModule $1 $2 $3 } : ''%module' defs { badModule $1 $2 }
badModule :: Comment [Def] -> Module badModule outer_comment defs = Module outer_comment fake_name defs where fake_name = "ERR - parser error reading module name"
Ideally the smart constructors should be in a monad that supports error logging like Writer.
As you can see this isn't a great way of doing things but I'm not sure you have any other options. Personally I'd see if I could live with "first fail" instead.
Best wishes
Stephen
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