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GHC/Error messages

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("Foo' is not a (visible) method of class `Bar'")
("Foo' is not a (visible) method of class `Bar'")
Line 12: Line 12:
 
This error message occurs when one tries to instantiate a class, but did not import the functions one tries to implement.
 
This error message occurs when one tries to instantiate a class, but did not import the functions one tries to implement.
  
Example: TODO
+
Example:
 +
<haskell>
 +
import Prelude hiding ((==))
 +
data Foo = Foo
 +
instance Eq Foo where
 +
    (==) a b = True
 +
</haskell>

Revision as of 17:07, 9 October 2009

GHC error messages and their meaning.

1 "Parse error in pattern"

TODO

Example: TODO


2 "Foo' is not a (visible) method of class `Bar'"

This error message occurs when one tries to instantiate a class, but did not import the functions one tries to implement.

Example:

import Prelude hiding ((==)) 
data Foo = Foo 
instance Eq Foo where 
    (==) a b = True