Learning Haskell with Chess

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Revision as of 08:28, 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.

1 Exercise 1 - data types

1.1 Learning targets

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

1.2 Tasks

• Define data types that represent boards (
  Board
  ), squares (
  Square
  ), positions (
  Pos
  ), pieces (
  Piece
  ) and game states (
  State
  ).
• Helium: Implement suited eq-functions.
• 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).

2 Exercise 2 - move generator

2.1 Learning targets

• list comprehension
• stepwise refinement

2.2 Tasks

3 Exercise 3 - gametree generation and minimax algorithm

3.1 Learning targets

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

3.2 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.