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# ychess
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ychess is a chess implementation and engine written in nim.
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## Quick Setup
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To play chess in the commandline simply download the code (or clone the
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repository) and run `nim c -r game.nim`.
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You can either play the 1v1 hotseat mode or a single player mode vs the engine.
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Additionally ychess uses the lichess api to make playing more convenient.
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An instance of the engine occasionally plays on
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[lichess](https://lichess.org/@/tiyn-ychess).
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To get into the whitelist just write a ingame message to the account.
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## Project Structure
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- `art` - contains pictures and arts not used in the code.
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- `bin` - is not pushed to the git repository but contains all binaries and will
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be created if you compile a program.
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- `htmldocs` - is not pushed to the git repository but contains all
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automatically generated documentation.
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- `src` - is the root folder for all programs except tests.
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- `tests` - contains all tests.
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### Documentation
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Documentation is written into the code via DocGen.
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For this reason it is not saved in this repository.
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To extract it into html (assuming you want the documentation for `game.nim`)
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run `nim doc --project --index:on --outdir:htmldocs game.nim`.
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## General Design Choices
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### Moves
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Moves are read from the commandline as [pure coordinate notation](https://www.chessprogramming.org/Algebraic_Chess_Notation#Pure_coordinate_notation).
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The inner program will convert this notation to a move-tuple.
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### Board Representation
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Due to easier off the board checking a
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[10x12](https://www.chessprogramming.org/10x12_Board) board is used.
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### Engine
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The engine uses a simple implementation of the
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[NegaMax](https://www.chessprogramming.org/NegaMax)-algorithm with
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[Alpha-Beta-Pruning](https://www.chessprogramming.org/Alpha-Beta#Negamax_Framework).
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For the evaluation function each piece has a corresponding value.
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Additionally [piece-square tables](https://www.chessprogramming.org/Piece-Square_Tables)
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are used.
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## Contributing
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### Setup
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To setup the project for development you need to create the file
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`src/secret.nim`.
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It should contain values for the following variables:
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```nim
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let projectdir* = "<absolute path to root dir of ychess>"
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let api_token* = "<lichess api token for bot>"
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```
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### Code Style Guide
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Basic arithmetic operations should be surrounded by spaces for example: `1 + 3`.
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This however is not true for negation of a single value (`-1`) or if the
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arithmetic operation is done inside array brackets or in iterators (`a+1..3`,
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`a[c+3]`).
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Determining the length of a string, array, etc should not be done via a function
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(`len(array)`) but by appending it like `array.len`.
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If statements should not contain outer brackets.
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In some cases (especially concatenations of `and` and `or`) inner brackets are
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useful to increase readability in complexer logic formulas.
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When assigning booleans with logical formulas outer brackets are expected.
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