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I define my own datatype.
data Row = A | B | C deriving (Show,Eq,Ord)
The question is, if there is a more elegant way to define my range than this?
instance Ix Row where
range (A,A) = [A]
range (A,B) = [A,B]
range (A,C) = [A,B,C]
range (B,B) = [B]
range (B,C) = [B,C]
range (C,C) = [C]
range _ = []
222
If you need to figure out what the type of an object is in a Haskell program, I hope this is helpful. Note that if you are in GHCI, you can just put :type before your expression to determine the expression's type, or use :set +t to see the type of every expression in GHCI.
One is of type (String,Int) , whereas the other is (Int,String) . This has implications for building up lists of tuples. We could very well have lists like [("a",1),("b",9),("c",9)] , but Haskell cannot have a list like [("a",1),(2,"b"),(9,"c")] .
One introduces, or declares, a type in Haskell via the data statement. In general a data declaration looks like: data [context =>] type tv1 ... tvi = con1 c1t1 c1t2...
In Haskell, every statement is considered as a mathematical expression and the category of this expression is called as a Type. You can say that "Type" is the data type of the expression used at compile time. To learn more about the Type, we will use the ":t" command.
There is: Derive Enum and define
range (x, y) = [x .. y]
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