[Haskell-cafe] Re: Patter matching beginner question

Tom Pledger tom at pledger.gen.nz
Mon Dec 17 05:12:43 EST 2007

Adam Smyczek <adam.smyczek <at> gmail.com> writes:
> But when I extract a and b to constants:
> c_a = "a" :: String
> c_b = "b" :: String
> case name of
> 	c_a -> ...
> 	c_b -> ...
> I get Patterns match(es) are overlapped.

Do you require 'name' and the constants to be of type String?

If not, you could get around the issue Brandon described by declaring a data
type for them:

    data Name = A | B

        case name of
            A -> ...
            B -> ...

The type system would then prevent A and B from being used in places where a
String is expected.  This may be an advantage, depending on the style of the
rest of the program.


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