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The Scala API docs for 2.10.3 say that I can, "Use refiy to produce the abstract syntax tree representing a given Scala expression." Accordingly, I can do:

scala> val uni = scala.reflect.runtime.universe 
uni: scala.reflect.api.JavaUniverse = scala.reflect.runtime.JavaUniverse@4e42766

scala> uni reify { 1 to 3 } 
res2: uni.Expr[scala.collection.immutable.Range.Inclusive] = Expr[scala.collection.immutable.Range.Inclusive](Predef.intWrapper(1).to(3))

In the example above, I get what I am looking for: Predef.intWrapper(1).to(3)) (a handy expanded representation of the operations to be performed).

When I attempt to reify 1 + 3, however, I do not the representation of the operations to perform that I desire.

scala> uni reify { 1 + 3 }
res5: uni.Expr[Int(4)] = Expr[Int(4)](4)

Is this expected behavior? Is + a primitive operation and, hence, not reified?

The Scala docs show an example of reification that implies that an even more useful representation is available:

reify{ 2 + 4 } // Apply( Select( Literal(Constant(2)), newTermName("$plus")), List( Literal(Constant(4)) ) )

How can I examine the proper expanded representation for 1 + 3 (if one exists) and how can I retrieve a detailed representation of any expression (immediately above)?

Edit: I see now that the representation show in the Scala docs is generated by showRaw. However, I still cannot reproduce the raw representation show in the example above for 2 + 4.

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1 回答 1

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请参阅Eugene Burmako 的回答：

宏被连接到类型检查（在宏参数在宏扩展之前进行类型检查的意义上），并且类型检查折叠常量

reify是使用宏实现的。

您应该只防止像这样的不断折叠：

{
  val i = 1
  showRaw{ reify{i + 2}.tree }
}
// Apply(Select(Ident(newTermName("i")), newTermName("$plus")), List(Literal(Constant(2))))
于 2014-01-24T19:24:30.870 回答