I’m trying to rap my head around why formal verification is useful? I’ve read that it reduces vulnerabilities in code but I’m puzzled by how it can do that, my understanding is you write a specification in another language that you can use to test your implementation for conformity to the spec but to me that alone wouldn’t make code better? What am I missing? Or is that the whole picture? I’ve read that multilingual people tend to be more logical, is the idea behind formal methods the same? Is it as simple as writing the same problem in two languages force you to think about the problem clearer?
Related
I want to optimize my angularjs frontend application and cleanup the code to provide better code quality.
I thought about bringing in more abstraction, since I implemented a lot of similiar looking, but slightly different controllers.
My question(s) are the following:
Are there common techniques to recognize bad code and optimize it?
How can one determine if code is either good, bad or redundant?
Where should one start, when trying to provide better code quality in
an existing software project?
To answer your questions:
Yes there are: by looking at the code itself experienced programmers can tell if the code has certain characteristics or not. Some metrics exist that could indicate alarm signals in terms of quality like "many dots" in object-oriented languages (same in Javascript) which indicates close coupling. Here is a comprehensive list.
By looking at it or as written before with static code analysis.
As others stated don't optimize or refactor just for the sake to have a good looking code base. When you need to touch existing code again to e.g. add a feature or fix a bug then start to look for code redundancies and many other signals that might indicate to refactor the code. Martin Fowler wrote an excellent book about it with step-by-step examples which IMO is a must-read for every developer. Also a good starting point is Misko's site. He talks about testability but "good" code is well testable.
What's really important before refactoring is to have a strong automated test base to rely on. If not add tests and go really slow to make sure you don't break existing functionality.
The topic is really huge and impossible to work through in a post here but I think it's one of the most important ones that makes an experienced programmer.
If a code is good or bad is your own opinion.
To make the code look better and more efficient I would do something like this:
Don't make the lines to long.
Use variables that make sense.
Use tabs and enter when it is too messy.
There are a whole lot more things to clean up your code, but these are just some examples.
If the code works - don't touch it :)
Then when you work on bug fixes or new features\changes - see if you can also gradually improve pieces of code you are working with. The more you work with the code the better understanding of overall picture you should get and opportunities to improve and optimize should become more obvious. (you should also continue learning from other sources - books, internet, other codebases)
There is now magic "one size fits all" solution :) but yes, you can start with simple style changes as suggested in the other answer.
The process you refer to is commonly known as Refactoring. There are a number of standard techniques for improving code; Martin Fowler's book "Refactoring" has a list, with examples.
Many popular IDEs have refactoring tools built-in.
One of the processes in agile development is known as "red/green/refactor". Red means your code doesn't pass its unit tests; green means it passes (i.e. it does what it's supposed to do), and "refactor" means you make it elegant, maintainable and clean. Because you have a unit test, you know the refactoring doesn't break the code.
Where to start is a tough question - I typically recommend refactoring when you're fixing bugs. You may as well write a unit test to expose the bug, and tidy up the code while fixing the bug. Because that module has a bug, it's likely to be high-risk, so you should improve the code quality.
I now have sufficent exposure to the Objective-C that if i'm stuck with anything, I know how to think of the problem in terms of a likely tool I need and go look for it. Simple really. There's A Method For That. So nothings a real problem anymore.
Now I'm looking deeper at the language in broader terms. We write stuff. The compiler hews out all the code to execute it. From a simple flashlight app thats a if/then decision to turn on, to a highly complex accelerometer driven 3D shoot 'em up with blood 'n guts and body parts following all sorts of physics, the compiler prepares the code ready to be executed like a giant railway layout. No matter how random it appears on the screen, everything possible can be generically described and prepared for.
So here's the question:
Are there cases where something completely unexpected to the software designer can still be handled without an execution halt? Maybe I'd better re-frame the question a few different ways: Can a ( objective-C ) program meta-compile within itself in response to an unplanned-for user request? or to re-put my opening remark, are there tools or methods for unlikely descriptions of unlikely problems?
I think #kfb has the right comment about metaprogramming. Check out the Runtime docs in conjunction with metaprogramming tutorials.
Parts of your last question might be in the realm of this doc.
If your looking for ways to reduce the size of your code base for the lesser used features, one idea might be to make the features internet based (assuming connectivity is not a problem).
i went through different questions on SO and was trying to find out what is the best way to design an application .I found that somewhere it was written that we should make the object of the class if it has a state this.
i found on the same page that utilities should be avoided so my question is how to implement the functionality. we can not create object because functionality can have and can not have state. and we can also not use static methods also. then how.
P.S---- my question can be layman bcoz i am newbie trying to learn/implement design patterns so whould be happy if somebody can provide me reading material,links with examples.
i know a bit of design patterns theoretically.
You're reading guidelines and treating them like mandates, which puts you in the impossible position of coding with rules that are too strict.
Guidelines are guidelines, and no more than that. If it's a good idea not to use utility classes, then don't use them a lot. Use them sparingly, where it makes sense.
If it's a bad idea (and it is) to use some global variables, then don't do it a lot. But if you need a static helper classes with a variable or two available to the app, then do it in that case.
Don't treat guidelines as law. Treat them as guidelines, and go against them when it makes sense. You will only gain this knowledge by programming. So start doing it, make mistakes, learn from it, and improve your code as you go. You won't get it done perfectly right from the start.
I have a game I wrote in Actionscript 3 I'm looking to port to iOS. The game has about 9k LOC spread across 150 classes, most of the classes are for data models, state handling and level generation all of which should be easy to port.
However, the thought of rejiggering the syntax by hand across all these files is none too appealing. Are there tools that can help me speed up this process?
I'm not looking for a magical tool here, nor am I looking for a cross compiler, I just want some help converting my source files.
I don't know of a tool, but this is the way I'd try and attack your problem if there really is a lot of (simple) code to convert. I'm sure my suggestion is not that useful on parts of the code that are very flash-specific (all the DisplayObject stuff?) and also not that useful on lots of your logic. But it would be fun to build! :-)
Partial automatic conversion should be possible, especially if the objects are just 'data containers', watch out for bringing too much as3-idiom over to objective-c though, it might not always be a good fit.
Unless you want to create your own (semi) parser for as3 you'd need some sort of a parser, apparently FlexPMD has one (never used it), and there probably are others.
After getting your hands on a parser you have to find some way of suggesting to the system what parts could be converted automatically. You could try and add rules to the parser/generator script for the general case. For more specific cases I'd use custom metadata on the actual class/property/method, assuming a real as3 parser would correctly parse those.
Now part of your work will shift from hand-converting files to hand-annotating files, but that might be ok for you.
Have the parser parse your classes and define actions based on your metadata that will determine what kind of objective-c class to generate. If you get this working it could at least get you all your classes, their simple properties and method signatures (getting the body of the methods converted might be a bit too much to ask but you could include it as a comment so you'd have a nice reference while hand-translating).
PS: if you make this into a one way process be very sure you don't need to re-generate it later - it would be bad if you find out that you have been modifying the generated code and somehow need to re-generate all those classes -- that would mean you'll have to redo all your hard work!
I've started putting a tool together to take the edge off the menial aspects of this process.
I'm trying to figure out if there's enough interest to make it clean and stable enough to release for others to use. I may just do it anyway.
http://meanwhileatthelab.blogspot.com.au/2012/08/automating-process-of-converting-as3-to.html
It's so far saving me a lot of time while porting one of my fairly large games from AS3 to objc.
Check out the Sparrow Framework. It's purported to be designed with Actionscript developers in mind, recreating classes that sort of emulate display list and things like that. You'll have to dive into some "rejiggering" for sure no matter what you do if you don't want to use the CS5 packager.
http://www.sparrow-framework.org/
even if some solution exists, note that architectural logic is DIFFERENT, and many more other details.
Anyway even if posible, You will have a strange hybrid.
I am coming back from WWDC2012, and the message is (as always..) performance anf great user experience.
So You should rewrite using a different programming model.
I asked this question about Microsoft .NET Libraries and the complexity of its source code. From what I'm reading, writing general purpose libraries and writing applications can be two different things. When writing libraries, you have to think about the client who could literally be everyone (supposing I release the library for use in the general public).
What kind of practices or theories or techniques are useful when learning to write libraries? Where do you learn to write code like the one in the .NET library? This looks like a "black art" which I don't know too much about.
That's a pretty subjective question, but here's on objective answer. The Framework Design Guidelines book (be sure to get the 2nd edition) is a very good book about how to write effective class libraries. The content is very good and the often dissenting annotations are thought-provoking. Every shop should have a copy of this book available.
You definitely need to watch Josh Bloch in his presentation How to Design a Good API & Why it Matters (1h 9m long). He is a Java guru but library design and object orientation are universal.
One piece of advice often ignored by library authors is to internalize costs. If something is hard to do, the library should do it. Too often I've seen the authors of a library push something hard onto the consumers of the API rather than solving it themselves. Instead, look for the hardest things and make sure the library does them or at least makes them very easy.
I will be paraphrasing from Effective C++ by Scott Meyers, which I have found to be the best advice I got:
Adhere to the principle of least astonishment: strive to provide classes whose operators and functions have a natural syntax and an intuitive semantics. Preserve consistency with the behavior of the built-in types: when in doubt, do as the ints do.
Recognize that anything somebody can do, they will do. They'll throw exceptions, they'll assign objects to themselves, they'll use objects before giving them values, they'll give objects values and never use them, they'll give them huge values, they'll give them tiny values, they'll give them null values. In general, if it will compile, somebody will do it. As a result, make your classes easy to use correctly and hard to use incorrectly. Accept that clients will make mistakes, and design your classes so you can prevent, detect, or correct such errors.
Strive for portable code. It's not much harder to write portable programs than to write unportable ones, and only rarely will the difference in performance be significant enough to justify unportable constructs.
Even programs designed for custom hardware often end up being ported, because stock hardware generally achieves an equivalent level of performance within a few years. Writing portable code allows you to switch platforms easily, to enlarge your client base, and to brag about supporting open systems. It also makes it easier to recover if you bet wrong in the operating system sweepstakes.
Design your code so that when changes are necessary, the impact is localized. Encapsulate as much as you can; make implementation details private.
Edit: I just noticed I very nearly duplicated what cherouvim had posted; sorry about that! But turns out we're linking to different speeches by Bloch, even if the subject is exactly the same. (cherouvim linked to a December 2005 talk, I to January 2007 one.) Well, I'll leave this answer here — you're probably best off by watching both and seeing how his message and way of presenting it has evolved :)
FWIW, I'd like to point to this Google Tech Talk by Joshua Bloch, who is a greatly respected guy in the Java world, and someone who has given speeches and written extensively on API design. (Oh, and designed some exceptionally good general purpose libraries, like the Java Collections Framework!)
Joshua Bloch, Google Tech Talks, January 24, 2007:
"How To Design A Good API and Why it
Matters" (the video is about 1 hour long)
You can also read many of the same ideas in his article Bumper-Sticker API Design (but I still recommend watching the presentation!)
(Seeing you come from the .NET side, I hope you don't let his Java background get in the way too much :-) This really is not Java-specific for the most part.)
Edit: Here's another 1½ minute bit of wisdom by Josh Bloch on why writing libraries is hard, and why it's still worth putting effort in it (economies of scale) — in a response to a question wondering, basically, "how hard can it be". (Part of a presentation about the Google Collections library, which is also totally worth watching, but more Java-centric.)
Krzysztof Cwalina's blog is a good starting place. His book, Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries, is probably the definitive work for .NET library design best practices.
http://blogs.msdn.com/kcwalina/
The number one rule is to treat API design just like UI design: gather information about how your users really use your UI/API, what they find helpful and what gets in their way. Use that information to improve the design. Start with users who can put up with API churn and gradually stabilize the API as it matures.
I wrote a few notes about what I've learned about API design here: http://www.natpryce.com/articles/000732.html
I'd start looking more into design patterns. You'll probably not going to find much use for some of them, but as you get deeper into your library design the patterns will become more applicable. I'd also pick up a copy of NDepend - a great code measuring utility which may help you decouple things better. You can use .NET libraries as an example, but, personally, i don't find them to be great design examples mostly due to their complexities. Also, start looking at some open source projects to see how they're layered and structured.
A couple of separate points:
The .NET Framework isn't a class library. It's a Framework. It's a set of types meant to not only provide functionality, but to be extended by your own code. For instance, it does provide you with the Stream abstract class, and with concrete implementations like the NetworkStream class, but it also provides you the WebRequest class and the means to extend it, so that WebRequest.Create("myschema://host/more") can produce an instance of your own class deriving from WebRequest, which can have its own GetResponse method returning its own class derived from WebResponse, such that calling GetResponseStream will return your own class derived from Stream!
And your callers will not need to know this is going on behind the scenes!
A separate point is that for most developers, creating a reusable library is not, and should not be the goal. The goal should be to write the code necessary to meet requirements. In the process, reusable code may be found. In that case, it should be refactored out into a separate library, where it can be reused in the future.
I go further than that (when permitted). I will usually wait until I find two pieces of code that actually do the same thing, or which overlap. Presumably both pieces of code have passed all their unit tests. I will then factor out the common code into a separate class library and run all the unit tests again. Assuming that they still pass, I've begun the creation of some reusable code that works (since the unit tests still pass).
This is in contrast to a lesson I learned in school, when the result of an entire project was a beautiful reusable library - with no code to reuse it.
(Of course, I'm sure it would have worked if any code had used it...)