为什么此通配符函数告诉我它的参数数量错误?

本文介绍了为什么此通配符函数告诉我它的参数数量错误?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

违规代码为:

<console>:47: error: wrong number of parameters; expected = 2 terms.foldLeft(r.unitA)(r.add(_, _.eval(x)))

我通过写来解决了我的问题:

I solved my problem by writing:

terms.foldLeft(r.unitA)((a,b) => r.add(a, b.eval(x)))

但是我仍然想知道是什么阻止了我的最初尝试?

But I'd still like to know what prevented my initial attempt?

推荐答案

这是SLS 6.23的部分:

Here is the section of the SLS 6.23:

iainmcgin.github.io/scala-ref-markdown/#placeholder-syntax-for-anonymous-functions

更新的链接:

www.scala-lang/files/archive/spec/2.11/06-expressions.html#placeholder-syntax-for-anonymous-functions

Daniel Sobral的帖子说:

Daniel Sobral's post says:

当您使用"_"作为占位符的匿名参数的占位符时 函数，该函数的范围是最里面的括号 包含它. 大部分时间.

"When you use "_" as a place holder for an anonymous parameter of a function, the scope of that function is the innermost parenthesis containing it. Most of the time.

更新自旋:我认为规范中的语法解释更容易理解，占位符不会转义封闭的Expr.有很多重复的问题.

Updated spin: I think the syntax explanation from the spec is easier to get, that the placeholder doesn't escape an enclosing Expr. There are various duplicate questions.