像String这样的方法的问题。替换是指用户会误以为发生了突变因为他可以忽略返回值。所以使用out参数作为“return”值。用户不能忽略这一点:

public class ImmutableList<T> {
  public ImmutableList(params T[] items) { 
    // ...
  }
  /// <summary>
  /// Creates a new list with the items in this list plus the supplied items.
  /// </summary>
  /// <param name="newList">
  /// The new list created for the operation.
  /// This is also the return value of this method.
  /// </param>
  /// <param name="items">Items to add to the new list.</param>
  /// <returns>The new list.</returns>
  public ImmutableList<T> Add(out ImmutableList<T> newList, params T[] items) {
    // ...
  }
}

用法:

var list = new ImmutableList<string>("Hello", "Immutable");
ImmutableList<string> newList;
list.Add(out newList, "World");

作为一名c++程序员和STL的爱好者，我提出了add_copy。(这也会建议remove_copy, replace_copy等等)

对于这种功能，我通常使用动词的第二种形式，在这种情况下是Added。

这个约定被Qt使用，例如QVector2D::normalized返回一个归一化的向量，而QVector2D::normalize则归一化一个向量。

以同样的方式，Added将返回带有新添加项的对象。

就我个人而言，我会把这个方法叫做Clone，把参数叫做AdditionalValue，因为这基本上就是它看起来在做的事情，而且很容易理解。

var empty = new ImmutableList<string>(); 
var list1 = empty.Clone("Hello"); 
var list2 = list1.Clone("immutable"); 
var list3 = list2.Clone("word");

我知道这似乎是在徒劳无益，但我认为您可能会以一种奇怪的方式来处理这个问题(因此命名困难)。当我有一个不可变的对象时，我通常不期望该对象具有暗示可变性的函数(如Add或AddAll)。我知道字符串和DateTime这样做，但即使我已经成为受害者，忘记使用DateTime / String函数的结果，所以我会尽可能避免这些陷阱。

如果我是您，我会遵循类似于Guava使用的Builder模式。参见Guava中的不可变集合。基本上，这个概念是用它所包含的所有内容来构造不可变对象。如果你想要创建一个新的不可变对象，你需要使用一个新的构建器。

var suite = new TestSuite.Builder<string, int>().add(newTest).build();

在用户调用构建之前，您可以扩展构建器以允许对测试套件进行各种修改(如果您愿意，可以使用标准列表命名约定，如添加/删除)。

This seems to come down to finding a word that expresses that the object is not modified. Also, that it is cloned and the element passed as a parameter is added to the end of the cloned list. Standard names like add and clone are never going to cover it. Perhaps clone_and_append which is also rather ambiguous, since the append part might imply that the parameter is appended to the original list. So it should probably be something like clone_and_append_to_clone or better yet append_to_clone, although this one does not really imply that the clone is going to be returned by this method, but rather that the clone already exists as part of the origina list.

因此，更多地考虑寻找一个不意味着对原始列表进行修改的名称，并建议创建一个新列表，考虑以下内容:

Offshoot -- var list1 = list.Offshoot("tail") - in the strictest sense, offshoot refers here to the new element and not the entire new list. Another apparent disadvantage is that it is not an action, the more correct name being list.CreateOffshoot. However, I find it gives a clear indication of the fact that the new list will contain the original list and that the new element will come at the end of the list. Spawn -- var list1 = list.Spawn("tail") - similar to the previous. The advantage is that it is an action, but there is a weaker implication that the new list will contain the original list. BranchOff -- var list1 = list.BranchOff("tail") - an action that suggests the original list will be cloned. One potential ambiguity is that it is not very clear how the parameter element will be used.