Re: Syntax checks

[Marius Vollmer]

Dirk Herrmann <address@hidden> writes:

> Hello everybody,
> 
> in the evaluator, there are a lot of syntax checks performed that could
> probably better be performed in a previous syntax checking phase, keeping
> the evaluator itself free of such checks.

This is a very interesting issue!

> * Removing unnecessary expressions from code would change the source in a
> way that can't be restored by unmemoizing.  Do we care?

I'd say, we needn't care.  Requiring that unmemoizing always works
perfectly will inhibit almost all interesting work towards a 'real'
compiler.

> In the long run we will probably want to allow more transformations
> on the source anyway for the sake of optimization.  Then,
> memoization/unmemoization won't work and we will have to provide a
> different mechanism to record the relationship between transformed
> code and the source.

Exactly.

> * Should warnings be issued when dead code is eliminated from the source?

Hmm, when the memoization is a distinct phase from execution, I'd say
we might emit warnings (when the user wants them), but when
memoization is intertwined with execution like it is now, the warnings
will come at unexpected times, I'm afraid, and might be more annoying
than helpful.  So, they should be off by default.

(more general musings in my reply to Neil...)