[Haskell-cafe] Type Directed Name Resolution

John Lask jvlask at hotmail.com
Thu Nov 11 20:16:26 EST 2010

On 12/11/2010 9:22 AM, Richard O'Keefe wrote:
> On 12/11/2010, at 2:17 AM, Michael Snoyman wrote:
>>> So why would you ever need to reuse the same field name in the same
>>> module?
>> data PetOwner
>> data FurnitureOwner
>> data Cat = Cat { owner :: PetOwner }
>> data Chair = Chair { owner :: FurnitureOwner }
>> Just the first thing that came to mind, this kind of thing comes up
>> often enough to be an irritant. I'm not sure whether or not TDNR is a
>> good solution to the problem, just pointing out a use case.
> I'm afraid it's not a *convincing* use case.
> It's not convincing because here "owner" *means different things*.

consider "length" ...

I have records with the attribute length, length can be given as an Int, 
Double, Float or maybe as a constructed type "Length", length's use as a 
record selector would also clash with List.length. All these have the 
same denotation.

should I then seporate into int_length, float_length, or use 
rec1_length, rec2_length etc etc...

for proper name space management why should I have to define each record
that defines a length field with different representation in distinct 
modules, or with different names for the field label when they denote 
the same thing?

This is easily handled in C, Pascal, PL/1, Cobol why not in Haskell ?

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