Learning Haskell with Chess

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: define equality functions (pattern matching)
  • Haskell: define instances of type classes Show, Eq
• pretty printing

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).

Exercise 2 - move generator

Learning targets

• list comprehension
• stepwise refinement

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.