scala-macros

问题 Let's imagine passing these two equivalent expressions to a Scala macro: with compiler-inferred implicit conversion: 1+"foo" with explicitly invoked implicit conversion: any2stringadd(1)+"foo" Is there a way to distinguish between these two inside the macro? 回答1: First of all, the 1 + "foo" case is going to be tricky because there isn't actually any implicit conversion happening there: Int itself really, truly does have this + method (unfortunately). So you're out of luck if that's your use

问题 For a DSL I would like to be able to do something like: object Creator { def create[T](s :String) :Foo[T] = macro createImpl[T] def createImpl[T](c :Context)(s :c.Expr[String]) : c.Expr[Foo[T]] = { reify(new Foo[Any]()) } } My problem is to replace the Any in reify with something that will return the correctly parametrized version. (above I use a string argument, but in the final version I plan to use the companion object of class T as a marker to know the argument-type of a Function1[T,Unit]

问题 Thanks to the answers to my previous question, I was able to create a function macro such that it returns a Map that maps each field name to its value of a class, e.g. ... trait Model case class User (name: String, age: Int, posts: List[String]) extends Model { val numPosts: Int = posts.length ... def foo = "bar" ... } So this command val myUser = User("Foo", 25, List("Lorem", "Ipsum")) myUser.asMap returns Map("name" -> "Foo", "age" -> 25, "posts" -> List("Lorem", "Ipsum"), "numPosts" -> 2)

问题 Update: I suspect that what I want might not be possible, and I've written up a blog post with my reasoning (and some alternatives) here. I'd be very happy to be told that I'm wrong. Suppose I want to create a instance of a trait using a factory method with a macro implementation. This method will take as an argument a path to a resource that the macro will read and parse (at compile time) into a map from strings to strings. That part is all fairly straightforward. Now suppose I want to

问题 I'm trying to answer this question. Instead of writing: case class Person(name: String, age: Int) { def this() = this("",1) } I thought I'd use macro annotations to expand it from: @Annotation case class Person(name: String, age: Int) So I tried adding the new constructor as a plain-old DefDef using quasiquotes in a macro annotation's impl, like: val newCtor = q"""def this() = this("", 1)""" val newBody = body :+ newCtor q"$mods class $name[..$tparams](..$first)(...$rest) extends ..$parents {

问题 I get the following error on sbt startup, when two specific sbt plugins are added together to a project in its build definition. One of these sbt plugins is scalikejdbc and the other is my own, and clearly their mutual inclusion in a project's build definition results in this error upon sbt startup: scala.reflect.internal.Types$TypeError: package macros contains object and package with same name: blackbox Clearly, it looks as if each plugin brings along a different version of scala.reflect

问题 Is there a scala library that can help colorize text written to the standard output? This library should take advantage of the scala string interpolation mechanic. 回答1: If you're using scala 2.11+ you can use this library : https://github.com/backuity/ansi-interpolator It uses a macro to transform your strings at compile time, and supports nesting: ansi"Text containing ansi tags such as %bold{bold text} or %underline{can be %yellow{nested}}" // you can also use string interpolation: val

问题 I'm on Scala 2.10.3 using Macro Paradise. I have a macro annotation where I'm trying to add a trait to on object, e.g: @MyAnnotation object Foo extends Bar {} After expansion I want something like: object Foo extends Bar with Baz {} Where Baz is a trait accessible in the compilation scope. Using macro paradise I can cleanly destructure my target tree: q"object $obj extends ..$bases { ..$body }" = tree where bases holds the existing extensions in the form List of Ident(newTypeName("Bar")) I

问题 I am trying to call a specialized collections library like FastUtil or Trove from generic Scala code. I would like to implement something like def openHashMap[@specialized K, @specialized V]: ${K}2${V}OpenHashMap = new ${K}2${V}OpenHashMap() Where the ${X} is clearly not valid Scala, but just my meta notation for text substitution, so that openHashMap[Long, Double] would return a Long2DoubleOpenHashMap the type would be known at compile time. Is this possible with Scala macros. If so, which

问题 I would like to print Scala source code of IF condition while being in THEN section. Example: IF{ 2 + 2 < 5 } THEN { println("I am in THEN because: " + sourceCodeOfCondition) } Let's skip THEN section right now, the question is: how to get source code of block after IF? I assume that IF should be a macro... Note: this question is redefined version of Macro to access source code of function at runtime where I described that { val i = 5; List(1, 2, 3); true }.logValueImpl works for me