Dynamic code creation

[Oliver Ruebenacker]

     Hello,

  I have a list List("a", "b", "c", ...) and I want to use TreeHugger to create code such as:

  object MyObject {

    val a = f("a")

    val b = f("b")

    val c = f("c")
    ...

  }

  The list is not known at compile time, so I can not hard-code the members of MyObject. How can I do this programmatically? The only examples I can find are completely static DSL. The ScalaDoc has no explanations and to understand how the DSL works behind the scenes is extremely hard.

  Thanks!

    

     Best,

     Oliver

--

Oliver Ruebenacker
Director of Computational Biology at PanGenX (http://www.pangenx.com)

Be always grateful, but never satisfied.

[eugene yokota]

I'm a bit confused. The entire library of treehugger is about generating Scala source code dynamically.

The examples in the doc (http://eed3si9n.com/treehugger/) tends to be static, since they are examples.

Many of the constructs documented with "..." accept vararg, including BLOCK.

See http://eed3si9n.com/treehugger/dsl.html

To make MyObject, you first need OBJECTDEF described here: http://eed3si9n.com/treehugger/object.html

import treehugger.forest._

import definitions._

import treehuggerDSL._

Welcome to Scala version 2.10.2 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_51).

Type in expressions to have them evaluated.

Type :help for more information.

scala> OBJECTDEF("MyObject") := BLOCK(

     |   LIT(0)

     | )

res0: treehugger.forest.ModuleDef = ModuleDef(Modifiers(, , Map()),MyObject,Template(List(),ValDef(Modifiers(private, , Map()),Ident(_),EmptyTree),List(Literal(Constant(0)))))

scala> treeToString(res0)

res1: String = 

object MyObject {

  0

}

Then you want vals: http://eed3si9n.com/treehugger/val.html

We can define a function that turns your List[String] dynamically:

scala> def foo(valStrings: List[String]): Tree =

     |   OBJECTDEF("MyObject") := BLOCK(valStrings map { x =>

     |     VAL(x) := LIT(0)

     |   }: _*)

foo: (valStrings: List[String])treehugger.forest.Tree

scala> treeToString(foo(List("a", "b", "c")))

res2: String = 

object MyObject {

  val a = 0

  val b = 0

  val c = 0

}

Finally you have a function application: http://eed3si9n.com/treehugger/apply.html

scala> def foo(valStrings: List[String]): Tree =

     |   OBJECTDEF("MyObject") := BLOCK(valStrings map { x =>

     |     VAL(x) := REF("f") APPLY (LIT(x))

     |   }: _*)

foo: (valStrings: List[String])treehugger.forest.Tree

scala> treeToString(foo(List("a", "b", "c")))

res3: String = 

object MyObject {

  val a = f("a")

  val b = f("b")

  val c = f("c")

}

Hope this helps.

-eugene

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