Hi,

Is there a feature to freeze variable assignment?

e.g.
a="hello"
a.assignfreeze
a="goodbye"  # ===> generates exception

Or, in a related vein, a type freeze, so that only similar objects can be added.

I realize that constants offer assignment freezing to a certain degree. 

The reason I ask, is that I stepped over-top of some framework
variables today, and it was hard to find out what was going on. Where
as ruby protects keywords, it would be nice if frameworks or custom
domain specific languages could do the same.

Thanks,
Nick