New Google Summer of Code student

[Valentin Tolmer]

Hello everyone,

My name is Valentin Tolmer, and I'm a student at the EPITA (a computer 
science school in Paris). I did an internship in January with Akim 
Demaille, to work on the precedence and associativity in Bison. This led 
to a small improvement : warnings for unused precedence and 
associativity in grammars.
I also started (but haven't finished yet) working on a graph tool to 
show in a clear way exactly what precedence relationships between tokens 
are used. All of that in order to simplify the precedence declarations 
and to detect unwanted conflict resolutions.
I am now working in a Google Summer of Code with the same objective, but 
this time with a bigger goal : introducing a new syntax for the 
precedence/associativity declaration part allowing for partial orders. 
The final idea is to be able to specify only the relationships used, to 
make the grammar clearer and to encourage reflexion about each 
relationship and the conflicts it solves.

So far, my work with Akim Demaille has led me to these considerations :
- We need to be able to prioritize one rule over another, not only one 
token over another
- We need to be able to give associativity specifically to a rule, not 
only to tokens
- We need to be able to declare partial order priorities
- And, of course, backwards compatibility

Please find attached an example of the new syntax (subject to further 
modification, of course).

I'm happy to start working on Bison again, and hope to have a great time 
with you!

Valentin Tolmer

new_syntax_2.y
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