ken 0.1.0

ken is a Haskell-like DSL in Scala:

import com.github.okomok.ken._

// From: http://www.haskell.org/haskellwiki/State_Monad

object StateGame extends Main {
    type GameValue = Int
    type GameState = (Bool, Int)

    // Pull the Monad explicitly.
    val _M = MonadState[State.apply[GameState]]
    import _M._

    val playGame: String => _M.apply[GameValue] = {
        case Nil => {
            for {
                (_, score) <- get
            } yield score
        }
        case x :: xs => {
            for {
                (on, score) <- get
                _ <- x match {
                    case 'a' if on => put(on, score + 1)
                    case 'b' if on => put(on, score - 1)
                    case 'c' => put(Bool.not(on), score)
                    case _ => put(on, score)
                }
            } playGame(xs)
        }
    }

    val startState = (False, 0)

    val main_ = IO.print { State.eval(playGame("abcaaacbbcabbab"))(startState) }
}

In ken, type-class instances are explicitly retrieved.

Rationale

• Foolishly honest port of Haskell standard libraries.
• Variance-aware.
• Pulling type-class instances explicitly so that wildcard imports are removed.
• Type-level functions for partially-applied types.

Maven Repository

• repository: http://okomok.github.com/maven-repo/releases
• group id: com.github.okomok
• artifact id: ken_2.9.1
• version: 0.1.0

In Scala 2.9.x, add -Ydependent-method-types to compiler options.

Links

• ekmett/functorial - GitHub
• Parsec
• runarorama/scarpia - GitHub
• scalaz
• Browse Source
• Browse Test Source
• The Scala Programming Language

Shunsuke Sogame <okomok@gmail.com>