codingame-hs-skeleton

Example project for the codingame-hs package.

Usage

1. Install it.

If you don’t have Git, you can also download the code by hand from GitHub using the same links.

$ git clone https://github.com/Chatanga/codingame-hs.git
$ git clone https://github.com/Chatanga/codingame-hs-skeleton.git

2. Provide your account informations.

Modify the credentials.json file as well as the first lines of code in Codingame.hs with your Codingame account informations. As you will see, the "Code of Kutulu" challenge has been used as an example for this skeleton, but it will work the same way with any other.

3. Build the project

You obviously already have Stack installed on your machine.

$ cd codingame-hs-skeleton
$ stack setup
$ stack build

4. Launch GHCI

$ stack ghci

Let start by playing a private game into the Codingame IDE.

λ> doPlay
Ranks: [1,0,3,2]
Game options: "seed=72353923\n"
Saved game result: 329737891

If you get a "Nothing returned" or an "internal error" result, it is probably because you didn’t have entered the corresponding challenge yet. To remedy this situation, just enter it by visiting the Codingame site competition section.

If all went well, you should have a LastBattles folder created in your working directory with a JSON file in it. That’s a game result named by its Game ID. If you bot follow the "# convention" explained below, you should be able to replay this game locally. Note that it is a replay, a post-mortem in other words. You can change the bot code along the way leading to potentially different output, but it won't change the replay itself. Your bot’s output is always ignored in a replay and it’s only a mean to debug a past game.

λ> doReplay 329737891
Two bots enter; one bot leaves!
WAIT
WAIT
WAIT
...
WAIT
Terminated

(The Game ID will obviously be different for you.)

Since the replay is local and use your bot as is, you can easily put breakpoints to understand its behavior, inspect any variable, produce meaningful diagrams to clarify things up, etc.

Once your bot is ready to enter the Arena, you can submit it.

λ> doSubmit
Agent ID: 9534321

If it is your first submit, just way one minute or two that enough games are played by the server before retrieving the list of your last completed battles.

λ> doList
Completed last battles:
329738649 - 0: DeCe07 (1986268), 1: Programming_Doge (1963033), 2: Galrauch (1957957), 3: Aries (2008136)
329738648 - 0: Akhaten (1957475), 1: vampiro (1957611), 2: avdg (1971085), 3: Aries (2008136)
329738647 - 0: Mitrandir (1962812), 1: pwlrfl (1960146), 2: ereiam (1957444), 3: Aries (2008136)
329738646 - 0: DirtyHarry (1957503), 1: Testeris (1957423), 2: Alpacah (1957534), 3: Aries (2008136)
329738645 - 0: Samsa (1957525), 1: cdurbin (1957499), 1: JohnnyYuge (1957401), 3: Aries (2008136)
329738644 - 0: DorianWilde (1957553), 1: BeberLeNewbie (1957519), 2: FrancoisMeme (1963607), 3: Aries (2008136)
329738643 - 0: Mugu-Mugu (1993182), 1: Snowbart (1957510), 2: Bob (1957529), 3: Aries (2008136)
329738642 - 0: SiR_Jonny (1991026), 1: Ben-oit (1962936), 2: nevgen (1957488), 3: Aries (2008136)
329738641 - 0: Risen (1957522), 1: SF (1957407), 2: kiwijam (1970416), 3: Aries (2008136)
329738640 - 0: miklla (1957437), 1: RiSuS (1957539), 2: MSmits (1957549), 3: Aries (2008136)

You can download any game result you are interested in by using its Game ID.

λ> doRetrieve 329738643
Ranks: [2,0,1,3]
Game options: "seed=33280016\n"
Saved game result: 329738643

The saved game result is now available for a local replay.

λ> :quit

The "# convention"

The skeleton uses the Haskell bootstrap code provided by Codingame for the "Code of Kutulu" contest with some minor modifications:

• The BotRunner module has been imported.
• A runMain = runBot True bot function (renamed as main by the packager) has been added.
• The original main function has been changed into a bot :: Bot function.
• The now unnecessary hSetBuffering stdout NoBuffering has been removed.
• Every direct access to stdin has been modified to use the provided readLine function.
• Every direct access to stdout has been modified to use the provided writeLine function.

With these changes, the bot will automatically echo on stderr its input with a # prefix. That’s all that matter here and it can obviously be done by other means. The benefit of the changes listed above are that they allow your bot to be used without additional modifications by the replay function in the Codingame module.

The reason why we need to echo the input back into stderr is simply that the game result omits stdin (and only provided stderr for your agents).