[Haskell-beginners] question about shared data types
Ian Knopke
ian.knopke at gmail.com
Mon Apr 29 12:28:03 CEST 2013
Hi everyone,
I have two modules that share a common data type in their respective data
structures:
package Aaa where
newtype Foo = Foo String
data Bar = Bar {
barFoo :: [Foo]
} deriving (Show, Eq)
...
package Bbb where
newtype Foo = Foo String
data Quux = Quux {
quuxFoo :: [Foo]
} deriving (Show, Eq)
...
Both modules require the Foo newtype defined. However, in all other
respects they are separate modules that can be used independently.
Defining the newtype Foo twice, as above, throws a compilation error
(ambigious reference). Importing one module inside another breaks
independence. I've been including newtype Foo in a Common.hs module that is
included in both, as I would in C or C++. This sort of thing can easily get
more complicated as the program grows however.
I was wondering if the Haskell community has a better solution to this that
I've overlooked.
Ian Knopke
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