在C＃和C ++我部经营差异++ [英] ++i operator difference in C# and C++

问题描述

我已经写在C ++和C＃下面的代码

I have the following code written in both C++ and C#

 int i=0;
 ++i = 11;

在此C＃编译器带来的误差

After this C# compiler brings an error

The left-hand side of an assignment must be a variable, property or indexer

不过，C ++编译器生成的代码没有错误，我得到的结果 11 为的值i 。这是什么差异的原因是什么？

But C++ compiler generate this code with no error and I got a result 11 for value of i. What's the reason of this difference?

推荐答案

不同的是，预先递增运算符为左值在C ++和是不是在C＃。结果
在C ++ ++我返回递增变量的引用。在C＃ ++我返回的变量i。结果
增加后的值因此，在这种情况下， ++我为左值在C ++和右值在C＃。

The difference is that pre-increment operator is lvalue in C++, and isn't in C#.
In C++ ++i returns a reference to the incremented variable. In C# ++i returns the incremented value of variable i.
So in this case ++i is lvalue in C++ and rvalue in C#.

从C ++规范有关前缀增量运营商

From C++ specification about prefix increment operator

类型的操作数应该是一个算术类型或指向一个
完全定义的对象类型。的值是
操作数的新值;它是一个左值

The type of the operand shall be an arithmetic type or a pointer to a completely-defined object type. The value is the new value of the operand; it is an lvalue.

PS 后缀增量运算符我++是不是。左值在C＃和C ++，所以这个代码行会在两种语言带来误差

P.S. postfix increment operator i++ isn't lvalue in both C# and C++, so this lines of code will bring error in both languages.

 int i=0;
 i++ = 11;

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