# Difference between revisions of "Learning Haskell with Chess"

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===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: | + | **Helium: equality and show functions (pattern matching) |

− | **Haskell: | + | **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 | + | **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.

## Contents

## 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.