Name clashes in record fields
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Question
error| Multiple declarations of ‘xxx’
I like to define:
data Human = Human {name :: String}
data Dog = Dog {name :: String}
Why is this forbidden?
I like to define:
data Human = Human {name :: String}
name :: Cat -> String
name = ...
Why is this forbidden, too?
Answer
The record field accessors name are just functions
that retrieve the field's value from a particular record.
They are in the global scope together with top-level functions
and thus cannot have the same name.
For resolving this you may:
- rename the accessor or the top-level function
- put the data declaration or the top-level function in another module and import qualified
- write a typeclass with a
namefunction and fit the non-accessor functionnamesomehow into that.
Using language extension
The GHC Users Guide has a DuplicateRecordFields section.. The extension (GHC 8.0.1+) allow definition of record types with identically-named fields.