Darren New <[EMAIL PROTECTED]> wrote: > I'm not sure what linear or uniqueness typing is. It's typestate, and if > I remember correctly the papers I read 10 years ago, the folks at > TJWatson that invented Hermes also invented the concept of typestate. > They at least claim to have coined the term.
Coining the term is one thing, but I feel pretty confident that the idea was not invented in 1986 with the Hermes language, but rather far earlier. Perhaps they may have invented the concept of considering it any different from other applications of types, though. I still have trouble delineating how to consider "typestate" different from ordinary types in formal terms, unless I make the formal model complex enough to include some kind of programmer-defined identifiers such as variables. The distinction is not at all relevant to common type system models based on the lambda calculus. While acknowledging, on the one hand, that the word "typestate" is used to describe this, I also object that types have *always* been assigned to expressions in differing type environments. Otherwise, it would be impossible to assign types to lambda abstractions in the simply typed lambda calculus, the simplest of all generally studied type systems. What is being named here is the overcoming of a limitation that programming language designers imposed upon themselves, whether from not understanding the theoretical research or not believing it important, I don't know. -- Chris Smith - Lead Software Developer / Technical Trainer MindIQ Corporation -- http://mail.python.org/mailman/listinfo/python-list
