if语句应该与ocaml中的else语句关联吗? [英] Should an if statement be associated with else statement in ocaml?

问题描述

在ocaml中，我希望每个条件都有许多嵌套的if语句和一个返回值.这样的代码变得越来越复杂.

In ocaml, I want to have many nested if statements and a return value on each of the conditions. The code is becoming complicated like this.

let func arg1 arg2 = 
   if condition1 then arg1+arg2
   else
   (
       //code1
       if condition2 then arg1*arg2
       else
       (
          //code2
          if condition3 then arg1+arg2
          else
          (
             //code3
          )
       )
   )

我可以有这样的代码来代替这样的嵌套语句吗?

Instead of such nested statements can I have code like this?

let func arg1 arg2 = 
   if condition1 then arg1+arg2
   //code1
   if condition2 then arg1*arg2
   //code2
   if condition3 then arg1+arg2
   //code3

推荐答案

OCaml是一种强类型和静态类型的语言，这意味着在编译时会检查每个表达式的类型.

OCaml is a strongly and statically typed language, which means that the type of every expression is checked at compile-time.

看看下面的代码片段.

if condition then true_value else false_value

在编译过程中，类型检查器将检查以下内容:

During compilation, the type-checker will check for the following:

1. condition必须具有类型bool;
2. true_value必须与false_value具有相同的类型；
3. 整个表达式的类型与true_value和false_value相同.

1. condition must have type bool;
2. true_value must have the same type as false_value;
3. The whole expression has the same type as true_value and false_value.

如果这些语句中的任何一个都不为真，则编译将失败并出现类型错误.

If any one of these statements is not true, then the compilation fails with a type error.

现在，让我们看一个没有else的if语句.

Now, let's take a look at a if statement, without a else.

if condition then true_value

如果条件为假，则表达式的计算结果为()，这是类型为unit的唯一值.使用前面的语句2和3，true_value在此处可以具有的唯一类型是unit.这意味着您不能将int或string或任何其他内容用作true_value.

If the condition is false, then the expression evaluates to (), the only value of type unit. Using statements 2 and 3 from before, the only type that true_value can have here is unit. That means that you can't use int or string or anything as the true_value.

通常，深度嵌套的if-else语句被视为代码异味:它可能表明您的代码需要重构.例如，OCaml提供模式匹配.取决于实际代码的样子，这可能是解决方法.

Usually, deeply nested if-else statements is considered a code smell: it may indicate that your code needs refactoring. For instance, OCaml offers pattern-matching. Depending on what your actual code looks like, it may be the way to go.

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