A slightly more readable (IMO) version (which won't fail to terminate
on infinite lists):
getTernaryRelationship (ls@[a,b,c]) = ...
getTernaryRelationship _ = error "getTernaryRelationship: not a ternary rel"
You can of course have type (a,a,a) -> (a,a,a) unless your other
functions require lists
/J
On 28 September 2010 16:07, Martin Tomko
Dear all, I want to have a function that acts only on lists of length 3 (I have a function that filters a list of lists and returns only those of that length). I guess I could change them into tuples (is there a way?), but anyway. Is there a way to specify in the signature that the function should only match such lists, or do I have to do pattern mattching in order to exclude other possibilities?:
getTernaryRelationship :: [a] -> [a] getTernaryRelationship ls = if (length ls /= 3) then error "not a ternary rel" else ...
thanks Martin
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