Skip to main content

交换两个int值的最短代码

CSDN上的帖子http://community.csdn.net/Expert/TopicView3.asp?id=4899577

比较好的是它着重考虑了“极端情况”----防止溢出

总结起来有如下几个
a^=b^=a^=b;
b=a+(a=b)*0;
a=b|a&~(b=a);
这三个在C#下应该都行,但是在C++下只有第一个行

原因是C#和C++对表达式求值顺序上不同,
如a=f(i)+g(i++)+h(i);中f,g用的都是i旧值,h则用的新值,C++则是未应义。
又如c=a+(a=1);C#中c应该是a旧值加1,C++则是2
C#中一个表达式中一个变量取值是按照从左至右的,C++则是按运算优先级的。

我觉得还是C#的顺序比较好,不过用C++多了总觉得它怪怪的。
另外C++未定义的那个太不好了,据说是因为编译器先于标准出现

Comments

Popular posts from this blog

Determine Perspective Lines With Off-page Vanishing Point

In perspective drawing, a vanishing point represents a group of parallel lines, in other words, a direction. For any point on the paper, if we want a line towards the same direction (in the 3d space), we simply draw a line through it and the vanishing point. But sometimes the vanishing point is too far away, such that it is outside the paper/canvas. In this example, we have a point P and two perspective lines L1 and L2. The vanishing point VP is naturally the intersection of L1 and L2. The task is to draw a line through P and VP, without having VP on the paper. I am aware of a few traditional solutions: 1. Use extra pieces of paper such that we can extend L1 and L2 until we see VP. 2. Draw everything in a smaller scale, such that we can see both P and VP on the paper. Draw the line and scale everything back. 3. Draw a perspective grid using the Brewer Method. #1 and #2 might be quite practical. #3 may not guarantee a solution, unless we can measure distances/p...

Qubes OS: First Impressions

A few days ago, while browsing security topics online, Qubes OS surfaced—whether via YouTube recommendations or search results, I can't recall precisely. Intrigued by its unique approach to security through compartmentalization, I delved into the documentation and watched some demos. My interest was piqued enough that I felt compelled to install it and give it a try firsthand. My overall first impression of Qubes OS is highly positive. Had I discovered it earlier, I might have reconsidered starting my hardware password manager project. Conceptually, Qubes OS is not much different from running a bunch of virtual machines simultaneously. However, its brilliance lies in the seamless desktop integration and the well-designed template system, making it far more user-friendly than a manual VM setup. I was particularly impressed by the concept of disposable VMs for temporary tasks and the clear separation of critical functions like networking (sys-net) and USB handling (sys-usb) into the...

Exploring Immutable Distros and Declarative Management

My current server setup, based on Debian Stable and Docker, has served me reliably for years. It's stable, familiar, and gets the job done. However, an intriguing article I revisited recently about Fedora CoreOS, rpm-ostree, and OSTree native containers sparked my curiosity and sent me down a rabbit hole exploring alternative approaches to system management. Could there be a better way? Core Goals & Requirements Before diving into new technologies, I wanted to define what "better" means for my use case: The base operating system must update automatically and reliably. Hosted services (applications) should be updatable either automatically or manually, depending on the service. Configuration and data files need to be easy to modify, and crucially, automatically tracked and backed up. Current Setup: Debian Stable + Docker My current infrastructure consists of several servers, all running Debian Stable. System Updates are andled automatically via unattended-upgrades. Se...