[Grace-core] On numbers and objects

[James Noble]

> I think all objects that have literals (Boolean, Number, String)  
> cannot have constructors. These objects pre-exist, and literals are  
> provided as constant references to those objects.

That seems OK for those three. The catch is that we hope to have
literals for things like Arrays or Lists - but will want to have  
"constructors"
for them too (I think!).  We'll also have something like "object  
literals"
(aka object construction expressions) but they (currently) don't have
constructors

> Objects that have constructors cannot have literals.


the catch there is we may want constructor *calls* that don't end up
creating a new object.  Hmm: perhaps I'm making more of a fuss about
this than I need to - our current plans mean that things like "class  
methods"
don't necessarily end up constructing and object anyway. Perhaps we can
incorporate that somehow into the design for immutable objects.

James