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

• 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

• Define a data type that represents a game tree (`GameTree`).
• 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.