宏在运行时访问函数的源代码 [英] Macro to access source code of function at runtime

问题描述

使用Scala宏，我想访问功能f的源代码.

Using Scala macros I would like to get access to source code of function f.

这是我的问题的简化示例:

Here is simplified example of my problem:

def logFImplementation(f: => Boolean) {
    val sourceCodeOfF: String = ... // <-- how to get source code of f??

    println("Scala source of f=" + sourceCodeOfF)
}

如此:

logFImplementation { val i = 5; List(1, 2, 3); true }

它应该打印:

Scala source of f=val i: Int = 5; immutable.this.List.apply[Int](1, 2, 3); true

(目前，我测试了 Macro，以便在运行时访问源代码文本，它对于{ val i = 5; List(1, 2, 3); true }.logValueImpl非常有用，但对于f.logValueImpl，它仅显示f.)

(Right now I tested Macro to access source code text at runtime and it works great for { val i = 5; List(1, 2, 3); true }.logValueImpl but for f.logValueImpl it just prints f.)

谢谢您的建议.

推荐答案

我认真怀疑是否有可能.

首先，宏是编译时.他们所做的只是变换程序组成的抽象语法树.这正是您能够执行{ val i = 5; List(1, 2, 3); true }.logValueImpl的原因:AST就在这里，因此将其打印为字符串没有困难.但是宏无法解析运行时值，因为在运行时没有 宏.

First, macros are compile-time thing. All they do is transform abstract syntax trees your program consists of. That's exactly the reason why you were able to do { val i = 5; List(1, 2, 3); true }.logValueImpl: AST is right here, so there is no difficulty printing it as string. But macros just can't resolve runtime values, because there are no macros at runtime.

第二，绝对没有理由相信f是Scala代码.我可以这样从Java调用您的函数(不确定我的名字正确无误，但想法仍然相同):

Second, there is absolutely no reason to believe that f is Scala code. I could call your function from Java like this (not sure that I got all names right, but the idea is still the same):

someObject.logFImplementation(new scala.Function0<Boolean>() {
    @Override
    public Boolean apply() {
        // do some things in Java
    }
});

(这是可能的，因为内部按名称调用参数被转换为scala.Function0对象).在这种情况下，您希望函数打印什么?

(and this is possible because internally call-by-name parameters are transformed into scala.Function0 objects). What would you expect your function to print in this case?

这篇关于宏在运行时访问函数的源代码的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！