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

14 Apr 2009


      1. data Color = Red | Green | Blue deriving (Show)
2. [Red,Black,White]

2009/4/14 michael rice :
...
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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Eugene Kirpichov
Web IR developer, market.yandex.ru