Difference between revisions of "Learning Haskell with Chess"

From HaskellWiki
Jump to: navigation, search
Line 5: Line 5:
 
===Learning targets===
 
===Learning targets===
 
*recapitulate Haskell types (keywords type and data, product and sum types)
 
*recapitulate Haskell types (keywords type and data, product and sum types)
**Helium: define equality functions (pattern matching)
+
**Helium: equality and show functions (pattern matching)
**Haskell: define instances of type classes Show, Eq
+
**Haskell: type classes (<hask>Show</hask>, <hask>Eq</hask>, <hask>deriving</hask>
 
*pretty printing
 
*pretty printing
   
 
===Tasks===
 
===Tasks===
*Define data types that represent boards (<hask>Board</hask>), squares (<hask>Square</hask>), positions (<hask>Pos</hask>), pieces (<hask>Piece</hask>) and game states (<hask>State</hask>).
+
*Define data types that represent boards (<hask>Board</hask>), squares (<hask>Square</hask>), positions (<hask>Pos</hask>), pieces (<hask>Piece</hask>, supported by <hask>PieceColor</hask> and <hask>PieceType</hask>) and game states (<hask>State</hask>).
*Helium: Implement suited eq-functions.
+
**Helium: Implement suited eq and show functions.
  +
**Haskell: Define/derive instances of <hask>Show</hask> and <hask>Eq</hask>
 
*Implement a function <hask>prettyBoard::Board->String</hask>, that transforms a board into a clearly arranged string representation (human readable :-)). Support this function with auxiliary functions that pretty print pieces, squares, ...
 
*Implement a function <hask>prettyBoard::Board->String</hask>, that transforms a board into a clearly arranged string representation (human readable :-)). Support this function with auxiliary functions that pretty print pieces, squares, ...
 
*Define the initial board (<hask>initialBoard::Board</hask>), test prettyBoard with initialBoard.
 
*Define the initial board (<hask>initialBoard::Board</hask>), test prettyBoard with initialBoard.

Revision as of 08:33, 19 March 2007

This page is about learning Haskell using the board game Chess as a running example. The complete code can be found at http://www.steffen-mazanek.de/dateien/projekte/hsChess.zip.

Exercise 1 - data types

Learning targets

  • recapitulate Haskell types (keywords type and data, product and sum types)
    • Helium: equality and show functions (pattern matching)
    • Haskell: type classes (Show, Eq, deriving
  • pretty printing

Tasks

  • Define data types that represent boards (Board), squares (Square), positions (Pos), pieces (Piece, supported by PieceColor and PieceType) and game states (State).
    • Helium: Implement suited eq and show functions.
    • Haskell: Define/derive instances of Show and Eq
  • Implement a function prettyBoard::Board->String, that transforms a board into a clearly arranged string representation (human readable :-)). Support this function with auxiliary functions that pretty print pieces, squares, ...
  • Define the initial board (initialBoard::Board), test prettyBoard with initialBoard.
  • Implement a simple evaluation function evalBoard::Board->Int as the difference of material on board (values: Pawn->1, Knight and Bishop->3, Queen->9, Rook->6, King->"infinity"=1000).

Exercise 2 - move generator

Learning targets

  • list comprehension
  • stepwise refinement

Tasks

Exercise 3 - gametree generation and minimax algorithm

Learning targets

  • break code in modules
  • complexity
  • recursive data structures -> recursive algorithms

Tasks

  • Define a data type that represents a game tree (GameTree).
  • Roughly estimate the number of nodes of the gametree with depth 4.
  • Define a function play::Gametree->Int, that computes the value of a given game tree using the minimax Algorithm.
  • Implement the function doMove::State->State, that choses the (best) next state.