Wednesday, June 29, 2005

tyeps, type constraint systems, strings, etc

I'll be checking in my notes shortly, but I figured that this wasn't going to fit into a margin...

In section 10.2, you discuss the correspondence between type constraint systems and non-deterministic finite automata.

It seemed from my reading that a type can be read as a (potentially infinite) tree, which in turn can be read as the set of strings that describe all paths from the root to the leaves of the tree. Thus, a type corresponds to a set of strings, or a single language.

In section 10.2, you say that there is a correspondence between type constraint systems and NFAs. But to me, a type constraint system describes not just one type, but rather a (potentially empty) set of types. Therefore, a type constraint system (TCS) corresponds to a set of languages, while an NFA corresponds to a single language.

Can you resolve this confusion for me (preferably by amending the paper with some sort of clarifying note)?

1 Comments:

Blogger pnkfelix said...

You misspelled tpyes.

A constraint system plus a choice of variable defines a type - such as "the upper bound for TAU in graph C". A transition relation plus a choice of start states defines an automaton - such as "go from q_0 in delta". (Both descriptions elide choice of domains: choice of type constructors and variables vs alphabet and states.) So a constraint set corresponds to a transition relation and a constrained variable (basically a type) corresponds to a full automaton.

I'll try to see how best to fit this into the paper.

4:56 PM  

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