Closed. This question is opinion-based. It is not currently accepting answers.
Want to improve this question? Update the question so it can be answered with facts and citations by editing this post.
Closed 8 years ago.
Improve this question
I'm developing a price calculation engine. I've looked all over and there's nothing that really fits what we need. However, I'm now looking how to implement specific prices and/or discounts. I don't want to introduce a rule based engine to my end-users, because they won't get it.
For example, when you order an ItemX the price is $30. But in combination with ItemY the price of ItemX is $20. Or when ordering five of ItemX, each after it will be only $15.
Any ideas on where to start? How to take this on? Perhaps some (open source) example applications that contain practices like these? Any (technical) patterns I could use? Preferably in C#.
Thanks in advance!
There are many ways you can achieve this, but I think the one which might be most useful for you would be to define a DSL that you can use to express your discounts in such a way where they can be easily explained and rationalised with business users. An example from one of ayende's articles on DSLs in boo is:
apply_discount_of 5.percent:
when order.Total > 1000 and customer.IsPreferred
when order.Total > 10000
suggest_registered_to_preferred:
when order.Total > 100 and not customer.IsPreferred
As you can see you can see, this is the kind of thing you can print out and show to a client and they will immediately understand what's going on.
Of course developing something like this is time consuming, expensive and fraught with funky edge cases. However it has the benefit of being code which can be unit tested, executed and debugged.
If boo isn't your thing, then maybe you could look at defining something similar in ironruby, ironpython or F#. I would however suggest staying away from XML for defining these rules unless you really enjoy a world of pain.
This is however the kind of thing that products like Biztalk were designed to handle. Which rules engines have you evaluated and found lacking?
We use a Rule Engine for this type of complex calculation. Our platform is Java and we use Drools (which we're happy with). Drools is also available for .Net. Here's a list of open source Rules Engines for .NET.
I am sorry to have to say this, but this would seem like you would have to apply some Pricing Rule Engine to achive what you are after.
Would seem like you have to
Store the available items, and their
discounts on per pruchase.
Store which items in combination
would discount each other.
Also maybe thinking of per
unit/quantity purchased per unit, or
maybe per package/special.
Might want to look at keeping a
archive/storage of these
specials/packages, just incase the
customer wants a reprint of the
original invoice.
In general there is a lot of possible rules/combinations that can be thought of, and you as developer can implement these and hide them from the user, or allow the user to create them, but somebody has to do so.
And then, when you dont feel like implementing your own, GOOGLE shold provide some:
Open Source Rule Engines
Related
Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 9 years ago.
Improve this question
i am preparing for my finals and came across this question:
Learn about the reflection mechanisms of Java, C# and Prolog, all of
which allow
a program to inspect and reason about its own symbol table at run time. How
complete are these mechanisms? (For example, can a program inspect symbols that
aren’t currently in scope?) What is reflection good for? What uses should be
considered good or bad programming practice?
Why is this question asked in terms of symbol table? Can i write the same solution that i write in terms of classes and objects like mentioned in this SO question:
What is reflection and why is it useful?
I think of reflection as the basic tool to do metaprogramming.
This turns out to be a declarative way to solve (a kind of) problems.
Sometime, instead of building a solution, can be useful to write something that allow to describe the problem space. That is, see if your problem can be restated in a more practical language.
You see, we treat languages as components of algorithms, like data. Then we can exchange components between languages.
Practically, an example of interesting Java/Prolog reflection is JPL
Some time ago I found useful - and performant - C# reflection. United to emit package allows to produce compiled code.
Prolog use reflection in seamless ways: for instance DCGs are really a 'simple' rewrite of declared rules.
I've started a project that I hope I will take me to Prolog controlling Qt interface,
of course Qt reflection plays a fundamental role.
edit About your question on symbol tables: symbol is an extremely general term. Also all languages have a concept of symbols, (maybe) differently aggregated. That's the core of languages. Then the question is perfectly posed in very general terms, just to check your understanding of these basic language concepts.
The "symbol table" is just an internal concept that is needed for "reflection" to do what it does: the ability of a program to examine itself at runtime and do something dynamically with that. (be aware about the diff between - introspection vs. reflection).
So if you understand what reflection is good for, how it is implemented in your target platform (Java, C# etc.), and what might be the limitations, you should be able to answer all those questions I suppose.
Think about the symbol table as just an "implementation detail" of a platform/runtime. According to the question above I don't think they expect you to know exactly how this is implemented.
I'd suggest you to read the following pages to get an idea of reflection in the corresponding language:
JAVA
C#
Prolog - Search for 'Reflection'
After Reading those you shold see similarities of the methods.
To be honest, I've never worked with reflection in Prolog, but the docs should guide you through.
The symobl table is used by the reflection mechanisms to look the things up.
See here for a description of symbol tables.
Those resources should give you an idea on how to answer your questions
Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.
We don’t allow questions seeking recommendations for books, tools, software libraries, and more. You can edit the question so it can be answered with facts and citations.
Closed 4 years ago.
Improve this question
I want to build a list of ~6 keywords (or even better: couple word keyphrases) for each message in a message forum.
The primary use of keywords is to replace subject lines in some instances. For example: Message from Terry sent Dec 5, keywords: norweigan blue, plumage, not dead
In a super ideal world keywords would identify both unique phases, and phrases that cluster the discussion into "topics", i.e. words that are highly relevant to the message in question, and a few other messages in the forum, but not found frequently in the forum as a whole.
I expect junk phrases to show up, no big deal.
Can't be too computationally expensive: I need something that can handle several hundred messages in several seconds, as I'll need to re-run this every time a new message comes in.
Anyone know a good C# library for accomplishing this? Maybe there's a way to bend Lucene.NET into providing this sort of info?
Or, failing that, can anyone suggest an algorithm (or set of algos) to read up on? If I'm implementing myself I need something not terribly complex, I can only tackle this if its tractable in about a week. Right now, the best I've found in terms of simple-but-effective is TF-IDF.
UPDATE: I've uploaded the results of using TF-IDF to select the top 5 keywords from a real dataset here: http://jsbin.com/oxanoc/2/edit#preview
The results are mediocre, but not totally useless... maybe with the addition of detecting multi-word phrases, this would be good enough.
I've implemented a keywords extraction algorithm in Java a few weeks ago for uni. project, and used the tf-idf model.
Algorithm:
First, we looked for all bigrams in the paragraph, and extracted the meaningful ones. (*)
Next, we took the set of unigrams and bigrams, and evaluated each with is respective tf-idf score. The idf score of each term was the "documents count" retrieved by Bing API.
(*) Deciding which bi-gram is meaningful:
We used a various heuristics to find which bi-gram can be considered meaningful. At the end, the best results were achieved by "asking" wikipedia: we searched for the bi-gram. If there is an article containing this bi-gram, we considered it meaningful.
Evaluation:
We evaluated the algorithm on a set of 50 abstracts from random articles, and extracted the precision and recall of these algorithms.
The result was ~40% recall and ~35% precision, which is not too bad.
Closed. This question is opinion-based. It is not currently accepting answers.
Want to improve this question? Update the question so it can be answered with facts and citations by editing this post.
Closed 4 years ago.
Improve this question
So a friend of mine has a small business, where he sells paper products, as well as custom posters, banners, and the like. He doesn't have a website, so he's hired me to create one for him, where users can place orders, check the status of their order, etc.
Other than his requirements, I'm trying to come up with other common functionalities that I should include in the site; things like a company blog, an admin section containing a simple CMS and error tracking/logging, a contact form, etc. Just common things that would be useful for a business site that he (or even I) might not think of.
Even small ideas are welcome. Someone suggested a global announcement module that would display a message on every page, for announcements like "Site maintenance from 1:00 - 4:00 tomorrow", or something like that.
Any other suggestions?
For a small business site I wouldn't even think of building it myself. Instead, just get a CMS like DotNetuke, or Drupal. Basically pick your poison.
All of the major ones have a number of free (and for sale) modules you can just drop in. Little things like shopping carts, blogs, photo carousels, etc.
Also, I wouldn't consider setting up a blog on the site unless the owner is going to commit to actually posting stuff to it.
All of this has been built a million times over and doing a custom solution for your friend is just going to hamstring him and lock you into doing updates. Ultimately you can set up a site in an afternoon with a decent skin for under $200 using one of the CMS's above. This is going to be far less than the amount of time you spend coding it yourself... And, I can pretty much guarantee he would end up with far more functionality than you could conceivably provide in any feasible amount of time.
Now if you just want to build your own CMS then I'd suggest doing it for your own site instead of his. Friends don't let Friends code when it's not necessary.
You could work on some design related ideas like pricing tables for his products or the ability for clients to be able to publisise the work he sells by creating links to DIGG, TWTITTER, FACEBOOK, etc.
Consider:
http://uxmovement.com/
It's an excellent design oriented blog that concentrates a lot on website and UI design.
Good luck!
Closed. This question is off-topic. It is not currently accepting answers.
Want to improve this question? Update the question so it's on-topic for Stack Overflow.
Closed 11 years ago.
Improve this question
A very open question. I've been programming in C# for the
past 5 months doing small projects that I completed
successfully.
Today I went to an interview for a C# role. The 1st question
was 'Tell me about boxing'. Given my experience I had no
idea what the guy meant. Needless to say the interview
didn't go that well. Others questions were 'why isn't it
recommended to use an ArrayList of int', 'tell me what you
know about threading', etc.
I don't really want this to happen again so I'm planning to
spend some time reading (and practising) more on C#. I
understand that the best way of learning is by coding but
coding wouldn't have really helped me answer the question
about 'boxing' for example.
I'm not asking you to answer the above technical questions.
In fact, I know now their answer as I went straight to
Google after the interview and it's how I realised that my
C# knowledge is somewhat limited.
My question is: in your opinion, which knowledge should any
C# developer have? Ideally it would be better if you could
categorize it (Basic knowledge anyone should have without
exception, Advanced knowledge, Expert knowledge etc). No need
to go into details. Doing research on whatever you list will
be a good exercise for me.
I would expect someone going for a professional C# job to know about:
Generics and generic collections
Interfaces (general)
Interfaces (specific), namely -
IDisposable: how it's integrated into the language and why
IEnumerable: including common extension methods, iterator blocks, and deferred execution
Overview of serialization in .Net (maybe not have done it, but understand what it is and know where to look in the namespace heirarchy and documentation)
Overview of Xml in .Net (same as serialization)
Overview of threading concepts (same as xml/serialization). Bonus points for understanding why most thread-safe collections aren't.
Have used anonymous delegates / lambdas in at least one project, and therefore also have a basic idea about closures.
Comfortable explaining some basic concepts from at least one of winforms, wpf, webforms, or MVC
Be able to answer some easy questions on specific common classes in the .Net BCL: namely from System.Data (think parameterized queries!) and System.IO (filestreams, path).
Garbage collection: when should you call GC.Collect (hint: pretty much never) and why
Here is a good list: What Great .NET Developers Ought To Know.
My personal experience from a long time ago when I was in school.
I went to see my father at work in a bank. At that time, most of his day was taking care of accounts and making sure every thing worked. What I saw was he was trying to tally/calculate large numbers and calculating(basic additions/multiplications...).
After noticing him, I asked him: Dad, if all you have to do is basic additions and multiplications, why bother to study till graduation?
His response was : While you don't have to use all the knowledge you have acquired, that knowledge would help you make learned decisions.
Coming to your question: While you dont have to use the entire set of concepts, knowing that they exist would help you make good decisions while you code.
My suggestion along with the others posted would be to try and spend some time on stackoverflow every day.
Good luck.
A good interviewer isn't going to grill you on trivia. That's why we have Google. A good interviewer is going to find areas you don't know, and ask you questions there, as that's the best place to find out how you react when confronted with something you don't have down pat.
The best advice I can give for interviews is to not worry about the technical trivia too much. Instead, in an interview, focus on problem-solving skills. If you don't know something, don't try to hide it, just admit it. If you think you know, it's okay to say "I'm not sure, but I think it's this." And don't get flummoxed either - at that point, usually the interviewer will give you a hint. This is not just giving you the answer, it's another part of the test - to see if, given a nudge in the right direction, you can extrapolate from there.
For the boxing/ArrayList/int questions, if I was interviewing and you didn't understand boxing, I'd give you a basic description of what boxing did. Then I'd ask you, knowing what I just told you, why you might think using ints in an ArrayList might be a bad idea.
One thing that will go far in any interview is focusing on the requirements, the desired result, and boundary conditions or edge cases. As most programming interview questions fall into the "write this method" category, make sure you get the following correct:
1) The inputs to the method
2) The expected output of the method
3) Boundary and edge cases.
This sounds ridiculously basic, but it's amazing how many developers, even ones with experience, don't bother thinking through these things. Code solves a problem - if you don't understand the problem correctly, you can't solve it correctly.
I would have to say that if an interviewer can be fooled into thinking someone has more .NET / C# experience by he or she visiting a webpage, then the interviewer is failing. I've interviewed a number of people myself, and I really like the approach of giving them some easy to understand problem to solve, and asking them to write some code on a white board. Even if they've memorized the answers to every question on Scott Hanselman's blog, I would learn a lot about how comfortable they are in the language, as well as how they go about problem solving. I'm looking for a developer, not a partner for Trivial Pursuit, .NET Developer Edition.
That said, keeping up with blogs like Hanselman's is a fantastic way to keep up with the jargon. You could code C# in a vacuum for years, fully understand the advantage of a strongly-typed List<int> over ArrayList, but never actually use the term "boxing". But it's much more time consuming in an interview to ask, "Describe the advantage of iterating through a List<int> instead of an ArrayList of int," than it is to ask, "Tell me about boxing." Plus, actually researching the answers to Hanselman's .NET interview questions (especially if you explore the details and ask "Why?") will make you a better developer. So by all means, keeping reading Hanselman.
And one more note... If I ask someone whether a String is a reference type or a value type, and they simply say "Hmmm... Reference type," I'm not going to be nearly as happy as I would if the response was, "Hmmm... Reference type, but that's an interesting question." "Why is that?", I say... "Because string is implemented so that the string is immutable, allowing you to do things with it like safely use it as a hash key. Or pass it to a method, knowing the value cannot be changed. So in a way, strings can act a lot like value types..." And that would be a great conversation, leading me to ask, "So tell me more about why hash keys should be immutable..."
It's not just the difference between answering a 50/50 question correctly and all the additional information in the second answer. Having an intelligent conversation with a interviewee leads me to think I'll have intelligent conversations like that on a regular basis once the interviewee becomes my coworker. And that's something I'm definitely looking for.
Also depends on the role. If this was advertised as a jnr role then a threading question is a little tough...sometimes agencies/employers have unrealistic expectations.
A similar thing happened to my significant other taking a driving test. The state trooper said, "make a roundabout" and she didn't know what he was talking about. Both of us think a roundabout is a type of road layout with a big circle, not a u-turn as the instructor meant. So I know what you mean.
Programming job interviews vary wildly. Some people think you can't really judge a programmer well in an interview and are willing to give anyone who makes a good impression a chance. Others are grueling things which only those overqualified for the position would pass, and you will probably be suprised how often you get a call back from those.
This is something I have been pondering myself a lot lately. Using C# plenty but not sure what I am missing.
I ordered
Microsoft® .NET Framework Application Development Foundation
Which covers a lot of ground related to C#
Also looking at C# in Depth
Read some of this already. Has some great information from a high quality author.
In depth is on sale too via Jon Skeet's blog
Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 8 years ago.
Improve this question
We're hiring a .NET developer soon, and I was assigned to create a test, which would take aprox: 1h to solve. A test which would test the programmers knowledge in (mainly) C# and ASP.NET.
This is what i've come up with so far:
Use project #1 to read data(HTML) from the specified URL and output all links(anchors) containing anchor name “xxxxxxxxx”. You are free to use 3rd party libraries. My main thought here was to test how the developer would go about solving the problem. For example:
Create a regex which would parse all the data needed.
Create a DOM-tree and use XPATH to find all anchor nodes.
Iterate the whole string and perform manual string compares.
Create a new solution where you demonstrate the usage of .NET masterpages.
Connect the solution to the ******** database. And output all customers from the “********_customers” table.
Create a new button which refreshes all users using AJAX.
Pretty basic stuff. Though, I also added the one below. Mainly to test the developers OO knowledge. Do you think this is too "overkill", or what kind of test would you suggest? If you were to hire a ASP.NET developer, what would your main focus be? ADO.NET? IO? string handling?
Create an interface/abstract class implementation demonstrating the functionallity of either the Factory, Factory Method, Command or Decorator pattern. You wont need to implement any functionallity, just use comments in your abstract class.
Thanks in advance!
The task you gave is essentially a day or two worth of coding if you want to have reasonably readable code. Within an hour I guess I would do it, but you'd have to read code that has cryptically named methods, unreadable regexes, weird callbacks, no error handling and overall is pretty darn ugly. Looking at it you would not hire me.
Before you give your question to candidates, first make sure that your peers/programmers can do it first. And that you can code it in less than 60 minutes in a way that would satisfy you.
That said, I do not know if test is the best choice for hiring anyone. A few interviewing bloggers wrote about their experience coming from conducting tons of interviews:
Guerilla Guide to Interviewing by Joel Spolksy
Truth about interviewing, Get that job at Google (and many others) by Steve Yegge
I totally agree with them. Having conducted about a gazillion of interviews myself, I find that asking basic technology related questions is not nearly as good as asking to implement a bit of recursion or pointers (if someone claims to know C/C++).
By hiring someone who understands recursion/algorithms you get a smart guy who can learn new technology. When you hire someone who knows how to connect to a database, who knows how to connect to a database but not necessarily qualified to do much more than that.
There are a few sources of good programming questions that are somewhere between coding and algorithms that may inspire you. They do not test .NET at all, but are very good indicator of smart programmers.
Top Coder
Google Code jam
Within 1 hour you can only test his programming skills, but it's not enough to write the code sample.
Take a look at this C# / ASP.NET MVC test:
http://tests4geeks.com/test/asp-net-mvc-c-sharp
After the applicant will pass the test and result will be good, then invite him to the interview and talk about his experience. Ask about most difficult features, that he implemented in his projects. In other words, you must understand, if he know and can do enough to take part in your project.
If you still want to ask him to write some code. That is some idea:
There are the students and subjects. Please ask to write 3 pages (asp .net mvc or web-forms). First and second - for editing the dictionary of students and subjects. Third form must contain be the table. The students are in left column. The subjects are in the top row. The marks are at the intersection. Each mark can be edited (text box) and saved. Saving could be implemented by clicking the common button "Save". Or it could save each cell automatically using the Ajax.
This is very simple example, but it would show you how user writes the code, what techniques does he use.
I would have thought that it would be better to simply create a test that would make it easy for you to put developers into different 'skill buckets'.
Why not have three or four sections or features that the developer must 'layer' features on top one another to show their programming and design skills.
Part 1: Implement x easy difficulty
features.
Part 2: Implement x medium difficulty
features.
Part 3: Implement x difficult
features.
Part 4: Implement x very difficult features.
And give the developer 1 hour to write the application. Make it realistic that they can implement the features in the given time frame.
As Joel and Jeff say on the Stackoverflow podcast, there is a direct correlation between developer skill and speed.
Think about the way exams are structured? We can all get 100% of the questions correct in any exam we sit if we had infinite time, but in 1 hour?
This way, If a developer takes your test and only implements features up to Section 2 in the time period, then you should have a safe indication that they are not suitable for the job. Section 3 features all done then they are good enough and section 4 complete would indicate that they are very experienced and a slight cut above the rest.
However I would also look at the overall polish that the developer has given to the code. If they implemented all features up to section 4, but poorly, then they are also not going to be someone you want. IF a developer only did up to section 3 but implemented everything very elegantly, then I would want to hire them.
I also think that 1 hour is perhaps a little too long. I would aim for 10-40 minutes obviously you may need to cut out section 4 that I proposed.
You should check
GeekInterview -- a good source for interview questions
There are hundreds of questions.
I think you would be much better off coming up with a single question that will allow you to see more than just development skills using your target technologies. Strong problem solving skills are as important as expertise in a specific technology stack.
I would even recommend that you explore the two aspects of a candidate in different parts of the process. I usually ask a bunch of questions about the technology stack we are using on our project to gauge the candidates level of knowledge as it relates to that stack.
Then I ask them a pure problem solving question and I allow them to use whichever technology they are most comfortable with to solve the problem (their choice of technology can be an important indicator).
I particularly like Graph Theory related problems. The candidates solutions will tell you a ton about how they approach, solve problems as well as how they validate their solutions.
As part of the problem solving portion of the interview you should be looking for:
Proper data structure design
Implementation of OO best practices
Proper solution (can they debug problems effectively... one great way to see this is do not allow them to use a computer, make them code on a whiteboard and debug in their heads)
Proper solution validation (do they come up with test cases)
My 2 cents:
We have a programming test in my company that is easy. Basically, you have to implement the listener pattern extending the ArrayList class, create unit tests for it (based on at least what we require), document the corner cases, document the program itself if you want to, and then send the test back to us.
A developer has 48 hours to complete that test. We ask for production quality in the test. We want to test the following items:
Was the developer smart enough to cover the corner cases?
Is the developer implementation of multi-threading satisfactory?
Are the unit tests good enough? Do they cover enough cases?
Is the code well written and documented? Will someone be able to maintain that code in the future?
Does he care about his code? Did he explain why he did "A" and not "B"?
I don't think short tests are capable of evaluating a developer. You may ask for a tool or technology that someone have not been using in the past months, and whoever is being tested for that technology will need sometime to get up to speed - but if a developer was working with that the day before, he will know by memory how to use it, and he/ she will seem smarter than the other developer, what may not be true.
But if you ask for something that is tricky and you are interviewing the developer, you can check how he is going to solve the problem - I don't think it really matters if he/ she cannot get the 100% right answer, as long as he/ she can talk about the problems that you found on the code and show that they actually understand whatever you explained to them.
In the past we have used problems from Google code jam. the problems in the early rounds are easier and they get gradually harder. They are kind of algorithmic in nature, you can solve them in whatever language you like. As they get harder there is often an obvious 'brute force' kind of answer that won't work because of the size of the data. So you have to think of something more optimal.
The first test you suggested should take 10min-40min for a basic dev - I would use a web-crawler I have in my library that converts HTML to XML then easily use Linq to XML.
I would test for lambda expressions, performance patterns maintain files, or writing an object to several files dynamically.
Maybe you would like to test unmanged code, pointers etc.
I donno, im just writing-jabbering while things are comin up to my mind, i wrote things that was hard for me to implement.
few days ago I was invited to pass C# programming test at skillbox website there was 30 questions quiz and 45 time to pass it. Below is some of them:
1) What will be printed by running the program?
#if DEBUG
Console.WriteLine("DEBUG");
#else
Console.WriteLine("RELEASE");
#endif
2) What will be the result of calling SomeMethod():
public static void SomeMethod()
{
string s1 = "a";
string s2 = "b";
Swap(ref s1, ref s2);
Console.WriteLine(s1);
Console.WriteLine(s2);
}
public static void Swap(ref Object a, ref Object b)
{
Object t = b;
b = a;
a = t;
}
Here is a link for reference, I think you can find more C# quezzes there http://skillbox.io