I am trying to dinamically interpret code given as a String. Eg:
val myString = "def f(x:Int):Int=x+1".
Im looking for a method that will return the real function out of it: Eg:
val myIncrementFunction = myDarkMagicFunctionThatWillBuildMyFunction(myString)
println(myIncrementFunction(3))
will print 4
Use case: I want to use some simple functions from that interpreted code later in my code. For example they can provide something like def fun(x: Int): Int = x + 1 as a string, then I use the interpreter to compile/execute that code and then I'd like to be able to use this fun(x) in a map for example.
The problem is that that function type is unknown for me, and this is one of the big problems because I need to cast back from IMain. I've read about reflection, type system and such, and after some googling I reached this point. Also I checked twitter's util-eval but I cant see too much from the docs and the examples in their tests, it's pretty the same thing.
If I know the type I can do something like
val settings = new Settings
val imain = new IMain(settings)
val res = imain.interpret("def f(x:Int):Int=x+1; val ret=f _ ")
val myF = imain.valueOfTerm("ret").get.asInstanceOf[Function[Int,Int]]
println(myF(2))
which works correctly and prints 3 but I am blocked by the problem I said above, that I dont know the type of the function, and this example works just because I casted to the type I used when I defined the string function for testing how IMain works.
Do you know any method how I could achieve this functionality ?
I'm a newbie so please excuse me if I wrote any mistakes.
Thanks
Ok, I managed to achieve the functionality I wanted, I am still looking for improving this code, but this snippet does what I want.
I used scala toolbox and quasiquotes
import scala.reflect.runtime.universe.{Quasiquote, runtimeMirror}
import scala.tools.reflect.ToolBox
object App {
def main(args: Array[String]): Unit = {
val mirror = runtimeMirror(getClass.getClassLoader)
val tb = ToolBox(mirror).mkToolBox()
val data = Array(1, 2, 3)
println("Data before function applied on it")
println(data.mkString(","))
println("Please enter the map function you want:")
val function = scala.io.StdIn.readLine()
val functionWrapper = "object FunctionWrapper { " + function + "}"
val functionSymbol = tb.define(tb.parse(functionWrapper).asInstanceOf[tb.u.ImplDef])
// Map each element using user specified function
val dataAfterFunctionApplied = data.map(x => tb.eval(q"$functionSymbol.function($x)"))
println("Data after function applied on it")
println(dataAfterFunctionApplied.mkString(","))
}
}
And here is the result in the terminal:
Data before function applied on it
1,2,3
Please enter the map function you want:
def function(x: Int): Int = x + 2
Data after function applied on it
3,4,5
Process finished with exit code 0