Re: [Haskell-cafe] Printing list of enum type

14 Apr 2009


      You don't need to add anything, you just need to use list notation
correctly. Try typing [Red, Black, White] in at the prompt instead. The
commas are part of the list syntax.

On Tue, Apr 14, 2009 at 9:15 AM, michael rice  wrote:
...
What do I need to add to this Color enum type to print a list of them?
Michael
===============
data Color
    = Red
    | Blue
    | Green
    | Yellow
    | Orange
    | Brown
    | White
    | Black
instance Show Color where
    show Red   = "Red"
    show Blue  = "Blue"
    show Green = "Green"
    show Yellow = "Yellow"
    show Orange = "Orange"
    show Brown = "Brown"
    show White = "White"
    show Black = "Black"
======================
Ok, modules loaded: Main.
*Main> Red
Red
*Main> Black
Black
*Main> [Red Black White]
<interactive>:1:1:
    Couldn't match expected type `Color -> Color -> t'
           against inferred type `Color'
    In the expression: Red Black White
    In the expression: [Red Black White]
    In the definition of `it': it = [Red Black White]
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Re: [Haskell-cafe] Printing list of enum type

Andrew Wagner