[Haskell-cafe] unique id for data types

Barney Hilken b.hilken at ntlworld.com
Tue Sep 18 07:11:43 EDT 2007

In order to make my records system practically useable, I need a type  

 >	type family NameCmp n m

which totally orders datatypes. More precisely, it should return one  
of the
following types:

 >	data NameLT = NameLT
 >	data NameEQ = NameEQ
 >	data NameGT = NameGT

for each pair of datatypes n & m, according to whether n < m, n = m,  
or n > m
in some global ordering. This ordering needs to be independent of the  
so it can't be affected by whatever imports there are in the current  

What I want to know is: does GHC give datatypes any global id I could  
use to
generate such an ordering? Would fully qualified names work?

Secondly (assuming it's possible) how easy would it be for me to  
write a patch
to add NameCmp to GHC? Where in the source should I start looking?



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