[Haskell-beginners] Dipping Toes Into Haskell

[Timothy Washington]

Thank-you :) And thanks for the Data.List docs. That's a good place to
start.


Tim Washington
Interruptsoftware.com <http://interruptsoftware.com>


On Thu, Mar 12, 2015 at 7:53 PM, Kim-Ee Yeoh <ky3 at atamo.com> wrote:

> Hi Tim,
>
> Congrats on your choice of tic-tac-toe. I also believe it's a good toy to
> get your feet wet with haskell.
>
> 1. Your concerns about writing a "custom datatype" are best addressed by
> reading up on it. If you search for "haskell data type declarations",
> you'll find good material explaining the difference between "data",
> "newtype", and "type" declarations. You'll also understand the meaning of
> the error message and what "data constructor" refers to.
>
> 2. Functions defined on lists are here:
>
> https://hackage.haskell.org/package/base/docs/Data-List.html
>
> The update function you're looking for is (!!).
>
>
>
>
> -- Kim-Ee
>
> On Fri, Mar 13, 2015 at 6:02 AM, Timothy Washington <twashing at gmail.com>
> wrote:
>
>> To get started, I'm trying to implement a simple *tictactoe* game. And I
>> would like to be able to represent a Piece on the board, as either the
>> string "X" or "O". This is what I have so far.
>>
>> module Main where
>>
>> data Piece = X | O
>> type Row = [Piece]
>> type Board = [Row]
>>
>> -- put an X or O in a position
>> move :: Board -> Piece -> Board
>> move board piece = board
>>
>> -- check win vertically
>> -- check win horizontally
>> -- check win diagonally
>>
>> main :: IO ()
>> main = putStrLn "Hello World"
>>
>>
>>
>> *A)* Now, I'd like to be able to *load code interactively*, preferably
>> within emacs. However I don't have access to my types with *ghci* or *ghc-mod
>> (Interactive-Haskell)*. In either case, this call fails with the below
>> error.
>>
>>
>> let p = Piece X
>> <interactive>:20:9-13: Not in scope: data constructor `Piece'
>>
>>
>> *B)* And how do I make a *custom datatype* that's one of two strings
>> (enumeration of either "X" or "O"). Cabal builds and runs the abouve code,
>> so I know it can compile. But I'm confused as to where X or O is defined,
>> and how I would supply it as an input.
>>
>> *C)* Finally, how do we update nested lists in Haskell. I want the move
>> function to take a Board, Piece, and Position, and return a Board. I see
>> some results from Hoogle <https://www.haskell.org/hoogle/?hoogle=update>.
>> Is this where Lenses <https://www.haskell.org/hoogle/?hoogle=lens> or
>> Zippers <https://www.haskell.org/hoogle/?hoogle=zipper> come into play?
>>
>>
>> Thanks
>>
>> Tim Washington
>> Interruptsoftware.com <http://interruptsoftware.com>
>>
>>
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>>
>>
>
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