Re: [Haskell-cafe] Eq macro which matches anything

4 Dec 2015


      On 5 December 2015 at 09:02, frantisek kocun  wrote:
...
Hi guys,
I'm doing Write yourself Scheme tutorial. And for testing it would be cool
to have some kind of macro.
-- My data type with Eq derived
data LispError = NumArgs Integer [LispVal]
               | TypeMismatch String LispVal
               | Parser ParseError
               | BadSpecialForm String LispVal
               | NotFunction String String
               | UnboundVar String String
               | Default String
               deriving (Eq)
-- I can call ==
NumArgs 1 [] == NumArgs 1 []
-- but sometimes I want to do (I know I can implement my own Eq, but I want
to use both forms)
NumArgs 1 [] == NumArgs 1 _
where I omit second parameter. I think derived Eq where it matches all the
args is fine I just need to do macro which will get whateverType by compiler
and always return True in Equality check. Do you think it is possible to do?
I use Mockito library in java but java is OO, so completely different beast.
Thank you
You could always define a new function:

eqError :: LispError -> LispError -> Bool
eqError (NumArgs n1 _) (NumArgs n2 _) = n1 == n2
eqError TypeMisMatch{} TypeMismatch{} = True
-- etc.
...
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Ivan Lazar Miljenovic
Ivan.Miljenovic@gmail.com
http://IvanMiljenovic.wordpress.com