15 Jan
2007
15 Jan
'07
4:16 a.m.
Hi Stefan,
myFunction x@(Constructor1 _*) = ... myFunction x@(Constructor2 _*) = ...
myFunction x@(Constructor1 {}) = myFunction x@(Constructor2 {}) =
myFunction2 (Constructor1 _* a _*) = ...
could be possible as long as the pattern is non-ambiguous (in this case, only one variable with the type of a is present in this constructor).
In this context a is not a type, but a value, and the non-ambiguous constraint can get pretty confusing in a case like this. The answer is to use records: data Data = Constructor1 {field1 :: Bool, field2 :: Int, field3 :: Int} myFunction (Constructor1 {field2=a}) = ... Thanks Neil