在 Scalaz7 中管理导入 [英] Managing imports in Scalaz7

问题描述

我在一个项目中使用 scalaz7，有时我会遇到导入问题.最简单的入门方法是

I am using scalaz7 in a project and sometimes I run into issues with imports. The simplest way get started is

import scalaz._
import Scalaz._

但有时这会导致冲突.直到现在我一直在做的以下有点痛苦的过程:

but sometimes this can lead to conflicts. What I have been doing until now the following slightly painful process:

• 找出一个需要与我的实际代码相同的导入的最小示例
• 将该示例复制到单独的项目中
• 使用选项 -Xprint:typer 编译它以找出隐式解析后代码的外观
• 在原始项目中导入所需的隐式.

• work out a minimal example that needs the same imports as my actual code
• copy that example in a separate project
• compile it with the option -Xprint:typer to find out how the code looks after implicit resolution
• import the needed implicits in the original project.

虽然这有效，但我想简化它.我看到 scalaz7 有更细粒度的导入，但我不完全理解它们是如何组织的.例如，我看到一个可以做

Although this works, I would like to streamline it. I see that scalaz7 has much more fine-grained imports, but I do not fully understand how they are organized. For instance, I see one can do

import scalaz.std.option._
import scalaz.std.AllInstances._
import scalaz.std.AllFunctions._
import scalaz.syntax.monad._
import scalaz.syntax.all._
import scalaz.syntax.std.boolean._
import scalaz.syntax.std.all._

等等.

这些子导入是如何组织的?

How are these sub-imports organized?

举个例子，假设我想使用验证.我需要什么，例如注入验证隐式并进行以下编译?

As an example, say I want to work with validations. What would I need, for instance to inject validation implicits and make the following compile?

3.fail[String]

如何使 ValidationNEL[A, B] 成为 Applicative 的实例?

What about making ValidationNEL[A, B] an instance of Applicative?

推荐答案

这篇博文详细解释了 scalaz7 中的包结构和导入点菜:http://eed3si9n.com/learning-scalaz-day13

This blog post explains the package structure and imports a la carte in scalaz7 in detail: http://eed3si9n.com/learning-scalaz-day13

对于您的具体示例，对于 3.failure[String]，您需要:

For your specific examples, for 3.failure[String] you'd need:

import scalaz.syntax.validation._

验证已经有一个方法ap:

scala> "hello".successNel[Int] ap ((s: String) => "x"+s).successNel[Int]
res1: scalaz.Validation[scalaz.NonEmptyList[Int],java.lang.String] = Success(xhello)

要获得 <*> 运算符，您需要导入:

To get the <*> operator, you need this import:

import scalaz.syntax.applicative._

然后你可以这样做:

"hello".successNel[Int] <*> ((s: String) => "x"+s).successNel[Int]

这篇关于在 Scalaz7 中管理导入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！