[Haskell-beginners] constant set

[Ovidiu Deac]

Thanks for the answers. I guess my example with the colors was misleading.
In that case it makes sense to use an abstract type.

In my case an abstract type is not ok. What I want is a set of int
constants i.e. some names for some ints that I will use in my code, to
avoid magic numbers in the code.

Of course I could define them like this:
red = 1
blue = 2

...but that would pollute the namespace

Also I don't want to define them in a separate file. I would like to define
them in the same file where I use them.

I already tried this approach:

module Main where

import ....

module Colors where
  red = 1
  blue = 2
.....

but the compiler complains at the line "module Colors where". It says:
parse error on input `module'


In Haskell this would usually be an abstract type:
>
>    data Color = Red | Blue | ...
>
> You could then use functions to convert between integers and colors.
>
>    fromColor :: Color -> Int
>    toColor   :: Int -> Maybe Color
>
> You could also derive an Enum instance and get the conversion functions
> 'fromEnum' and 'toEnum' for free, although in that case the 'toEnum'
> function is less safe (no Maybe):
>
>    data Color = Red | Blue | ...
>                 deriving Enum
>
>    fromEnum :: Color -> Int
>    toEnum   :: Int -> Color
>
>
> Greets,
> Ertugrul
>
> --
> nightmare = unsafePerformIO (getWrongWife >>= sex)
> http://ertes.de/
>
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>
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