What are invariants, how can they be used, and have you ever used it in your program?

Posted by gablin on Programmers See other posts from Programmers or by gablin
Published on 2010-12-30T21:19:20Z Indexed on 2010/12/30 22:00 UTC
Read the original article Hit count: 194

Filed under:

programming

|

invariants

I'm reading Coders at Work, and in it there's a lot of talk about invariants. As far as I've understood it, an invariant is a condition which holds both before and after an expression. They're, among other things, useful in proving that loop is correct, if I remember my Logic course correctly.

Is my description correct, or have I missed something? Have you ever used them in your program? And if so, how did they benefit?

© Programmers or respective owner

Related posts about programming

Imperative Programming v/s Declarative Programming v/s Functional Programming

as seen on Geeks with Blogs - Search for 'Geeks with Blogs'
Imperative Programming :: Imperative programming is a programming paradigm that describes computation in terms of statements that change a program state. In much the same way as the imperative mood in natural languages expresses commands to take action, imperative programs define sequences of commands… >>> More
Programming in python Vs programming in Java

as seen on Stack Overflow - Search for 'Stack Overflow'
I've been writing Java for the last couple of years , and now I've started to write in python (in addition). The problem is that when I look at my Python code it looks like someone tried to hammer Java code into a python format , and it comes out crappy because - well , python ain't Java. Any… >>> More
Have you ever bought a commercial implementation of a programming language for personal programming

as seen on Stack Overflow - Search for 'Stack Overflow'
Commercial products are often a source of ideas and inspiration for open source projects. There are free and open source implementations of almost every programming language ever devised, and a lot of them are very good. For non-work related personal programming projects, have you ever bought an… >>> More
Is Game Programming very different from normal programming?

as seen on Stack Overflow - Search for 'Stack Overflow'
By normal programming, I'm referring to application programming (which is all I'm familiar with at the moment). My goal is to make games, and I wanted to know if the path was different than other programming paths at the beginner level. Or perhaps it's too early for me to worry about that at this… >>> More
Programming activities for high school kids who have no idea what CS or programming is

as seen on Stack Overflow - Search for 'Stack Overflow'
I work at a small high school that's in a very high poverty area. There are only a handful of seniors that are thinking about applying to be an engineer of some sort in college and only 1 kid that applied for Computer Science (he has a couple acceptances so far!). He's been talking to me a lot as… >>> More

Related posts about invariants

Common mistakes which lead to corrupted invariants

as seen on Programmers - Search for 'Programmers'
My main source of income is web development and through this I have come to enjoy the wonders of programming as my knowledge of different languages has increased over the years through work and personal play. At some point I reached a decision that my college education was not enough and that I wanted… >>> More
Why are invariants important in Computer Science

as seen on Programmers - Search for 'Programmers'
I understand 'invariant' in its literal sense. I also recognize them when I type code. But I don't think I understand the importance of this term in the context of computer science. Whenever I read conversations\white papers about language design from famous programmers\computer scientists, the… >>> More
Beginner question - Loop invariants (Specifically Ch.3 of "Accelerated C++")

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi - as I said, a complete beginner question here. I'm currently working my way through "Accelerated C++" and just came across this in chapter 3: // invariant: // we have read count grades so far, and // sum is the sum of the first count grades while (cin >> x) { ++count; sum +=… >>> More
Code Contracts Preview: Invariants

as seen on Dot net Slackers - Search for 'Dot net Slackers'
In this article, I'll go through the concept and implementation of class invariants as supported by the .NET Framework 4 Code Contracts API. >>> More
DDD: Client-side script to enforce invariants

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello, One thing that I'm confused about in regards to DDD is that our domain is supposed to handle all business logic and enforce invariants. I have noticed some people (me included) handle certain invariants in the presentation layer (i.e. WebForms, Views, etc) with javascript. This is mainly… >>> More