Re: [Haskell-beginners] what is a qualified type?

On Thu, Aug 9, 2012 at 10:42 PM, Christopher Howard wrote:

On 08/09/2012 06:54 PM, Antoine Latter wrote:

...

On Thu, Aug 9, 2012 at 9:56 PM, Christopher Howard wrote:

In what context are you seeing the term used?

Antoine

I'm pulling the term vaguely from memory. The idea had something to do, I think, with a type that has no other purpose than to qualify another type, and somehow makes the programming more safe. I'm not referring to qualified module imports, as someone suggested.

Perhaps you're thinking of phantom types? They can be used like that. http://www.haskell.org/haskellwiki/Phantom_type

In my mind it is associated with "safe constructors" (another concept I am relearning) but I'm not sure if the two concepts are actually related.

I know there is a book called "Qualified Types: Theory and Practice" by Mark Jones http://web.cecs.pdx.edu/~mpj/pubs/thesis.html but I haven't read it.

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