Hi there.
I’m currently in the initial phases of developing a game, where I want to use an AI module I wrote as a project some years back.
The problem is: the module is written in Scala. It has a lot of immutable-set operations, recursively-defined structures (e.g. propositional logical formulae) and includes a parser. In other words it is the sort of computations that functional programming is great for. I’ve given a few code examples at the bottom to illustrate.
What would be the best way to include functional programming in a cocos2d-x project? I’ve thought of the following approaches:
- Re-write the module in F#, and compile as a .dll referenced from the game solution (I’m working on Visual Studio 2013). This should work fine for the win32 compilation of the project, but I am unsure what will happen when deployed to an android or ios device?
- Re-write in some other language which may have native cross-platform usage. Haskell? Lisp? Some other alternative? I’m not above learning a new syntax to get this done.
- Rewrite the whole module in C++ to include in my game. I would like to avoid this, since it would be a huge pain to translate to another paradigm and would likely become very bloated/hard to understand compared to the current functional syntax. I might be wrong here and it may be possible to write clean and functional code in C++ without me knowing it.
- Write in something else and translate to C++. I am unsure how this would work behind-the-scenes and how hard it would be to optimize the code later on, but it may be the way forward. HaskC++ seems to be something along these lines.
My primary problem is that I am simply not proficient enough in what happends deeper inside Cocos2d-x in it’s cross-platform magic to know how much I can stretch it. Can you help? 
Code Examples:
Recursive type-definitions:
class Formula() {
def and(q:Formula) = Conjunction(this, q) // ∧
def or(q:Formula) = Disjunction(this,q) // ∨
def impl(q:Formula) = Implication(this,q) // →
def not = Not(this) // ¬
def B(i:String) = Believes(i, this)
def E(a:Set[String]) = EveryoneBelieves(a, this)
def C(a:Set[String]) = CommonKnowledge(a, this)
}
Parser:
class mapParser extends RegexParsers {
val disjOp = "|"
val conjOp = "&"
val negOp = "~"
val kOp = "B"
val eOp = "E"
val cOp = "C"
val separator = "_"
val listseparator = ","
def lit:Parser[String] = "[a-z][a-z_0-9]*".r // fluents are never capitalized. but may have underscore.
def litargs: Parser[String] = repsep(arg,listseparator) ^^ {case list => list.toString.stripPrefix("List").replace(", ",",")}
def arg = agent | variable
def args:Parser[List[String]] = leftparen~>repsep(arg,listseparator)<~rightparen
def argSet:Parser[Set[String]] = leftbracket~>repsep(arg,listseparator)<~rightbracket ^^ { case a => a.toSet }
...