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  • Need explanation on theorem form the book [closed]

    - by Pradeep
    I need some explanation on amortization analysis with respect to analysis of algorithm. I need some more explanation on one of the theorem attached. Explanation needed: 1. How did the author derive at Mij is O (ij-ij-1)? 2. Need explanation for quoted from the book " because at most ij-ij-1 -1 elements have been added into the table since the clear operation Mij-1 or since the beginning of the series." 3. Also what does the summation equation mean? need some more thorough explanation and the essence of the theorem. Removed Attached is the scan copy of the page from the Book

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  • What's a nice explanation for recursion?

    - by Gulshan
    This question is inspired by What's a nice explanation for pointers? So, what can be a nice explanation of the recursion? Update: The idea of recursion is not very common in real world. So, it seems a bit confusing to the novice programmers. Though, I guess, they become used to the concept gradually. So, what can be a nice explanation for them to grasp the idea easily? I expected some detailed answers. N.B. : Even I am going to post one answer. But to be fair, it will be few hours later.

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  • single for-loop runtime explanation problem

    - by owwyess
    I am analyzing some running times of different for-loops, and as I'm getting more knowledge, I'm curious to understand this problem which I have still yet to find out. I have this exercise called "How many stars are printed": for (int i = N; i > 1; i = i/2) System.out.println("*"); The answers to pick from is A: ~log N B: ~N C: ~N log N D: ~0.5N^2 So the answer should be A and I agree to that, but on the other side.. Let's say N = 500 what would Log N then be? It would be 2.7. So what if we say that N=500 on our exercise above? That would most definitely print more han 2.7 stars? How is that related? Because it makes sense to say that if the for-loop looked like this: for (int i = 0; i < N; i++) it would print N stars. I hope to find an explanation for this here, maybe I'm interpreting all these things wrong and thinking about it in a bad way. Thanks in advance.

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  • What's a nice explanation for pointers?

    - by Macneil
    In your own studies (on your own, or for a class) did you have an "ah ha" moment when you finally, really understood pointers? Do you have an explanation you use for beginner programmers that seems particularly effective? For example, when beginners first encounter pointers in C, they might just add &s and *s until it compiles (as I myself once did). Maybe it was a picture, or a really well motivated example, that made pointers "click" for you or your student. What was it, and what did you try before that didn't seem to work? Were any topics prerequisites (e.g. structs, or arrays)? In other words, what was necessary to understand the meaning of &s and *, when you could use them with confidence? Learning the syntax and terminology or the use cases isn't enough, at some point the idea needs to be internalized. Update: I really like the answers so far; please keep them coming. There are a lot of great perspectives here, but I think many are good explanations/slogans for ourselves after we've internalized the concept. I'm looking for the detailed contexts and circumstances when it dawned on you. For example: I only somewhat understood pointers syntactically in C. I heard two of my friends explaining pointers to another friend, who asked why a struct was passed with a pointer. The first friend talked about how it needed to be referenced and modified, but it was just a short comment from the other friend where it hit me: "It's also more efficient." Passing 4 bytes instead of 16 bytes was the final conceptual shift I needed.

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  • clear explanation sought: throw() and stack unwinding

    - by Jerry Gagelman
    I'm not a programmer but have learned a lot watching others. I am writing wrapper classes to simplify things with a really technical API that I'm working with. Its routines return error codes, and I have a function that converts those to strings: static const char* LibErrString(int errno); For uniformity I decided to have member of my classes throw an exception when an error is encountered. I created a class: struct MyExcept : public std::exception { const char* errstr_; const char* what() const throw() {return errstr_;} MyExcept(const char* errstr) : errstr_(errstr) {} }; Then, in one of my classes: class Foo { public: void bar() { int err = SomeAPIRoutine(...); if (err != SUCCESS) throw MyExcept(LibErrString(err)); // otherwise... } }; The whole thing works perfectly: if SomeAPIRoutine returns an error, a try-catch block around the call to Foo::bar catches a standard exception with the correct error string in what(). Then I wanted the member to give more information: void Foo::bar() { char adieu[128]; int err = SomeAPIRoutine(...); if (err != SUCCESS) { std::strcpy(adieu,"In Foo::bar... "); std::strcat(adieu,LibErrString(err)); throw MyExcept((const char*)adieu); } // otherwise... } However, when SomeAPIRoutine returns an error, the what() string returned by the exception contains only garbage. It occurred to me that the problem could be due to adieu going out of scope once the throw is called. I changed the code by moving adieu out of the member definition and making it an attribute of the class Foo. After this, the whole thing worked perfectly: a try-call block around a call to Foo::bar that catches an exception has the correct (expanded) string in what(). Finally, my question: what exactly is popped off the stack (in sequence) when the exception is thrown in the if-block when the stack "unwinds?" As I mentioned above, I'm a mathematician, not a programmer. I could use a really lucid explanation of what goes onto the stack (in sequence) when this C++ gets converted into running machine code.

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  • SQL SERVER – QUOTED_IDENTIFIER ON/OFF Explanation and Example – Question on Real World Usage

    - by Pinal Dave
    This is a follow up blog post of SQL SERVER – QUOTED_IDENTIFIER ON/OFF and ANSI_NULL ON/OFF Explanation. I wrote that blog six years ago and I had plans that I will write a follow up blog post of the same. Today, when I was going over my to-do list and I was surprised that I had an item there which was six years old and I never got to do that. In the earlier blog post I wrote about exploitation of the Quoted Identifier and ANSI Null. In this blog post we will see a quick example of Quoted Identifier. However, before we continue this blog post, let us see a refresh what both of Quoted Identifider do. QUOTED IDENTIFIER ON/OFF This option specifies the setting for use of double quotes. When this is on, double quotation mark is used as part of the SQL Server identifier (object name). This can be useful in situations in which identifiers are also SQL Server reserved words. In simple words when we have QUOTED IDENTIFIER ON, anything which is wrapped in double quotes becomes an object. E.g. -- The following will work SET QUOTED_IDENTIFIER ON GO CREATE DATABASE "Test1" GO -- The following will throw an error about Incorrect syntax near 'Test2'. SET QUOTED_IDENTIFIER OFF GO CREATE DATABASE "Test2" GO This feature is particularly helpful when we are working with reserved keywords in SQL Server. For example if you have to create a database with the name VARCHAR or INT or DATABASE you may want to put double quotes around your database name and turn on quoted identifiers to create a database with the such name. Personally, I do not think so anybody will ever create a database with the reserve keywords intentionally, as it will just lead to confusion. Here is another example to give you further clarity about how Quoted Idenifier setting works with SELECT statement. -- The following will throw an error about Invalid column name 'Column'. SET QUOTED_IDENTIFIER ON GO SELECT "Column" GO -- The following will work SET QUOTED_IDENTIFIER OFF GO SELECT "Column" GO Personally, I always use the following method to create database as it works irrespective of what is the quoted identifier’s status. It always creates objects with my desire name whenever I would like to create. CREATE DATABASE [Test3] I believe the future of the quoted identifier on or off is useful in the real world when we have script generated from another database where this setting was ON and we have to now execute the same script again in our environment again. Question to you - I personally have never used this feature as I mentioned earlier. I believe this feature is there to support the scripts which are generated in another SQL Database or generate the script for other database. Do you have a real world scenario where we need to turn on or off Quoted Identifiers. Click to Download Scripts Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • I owe you an explanation

    - by Blueberry Coder
    Welcome to my blog! I am Frédéric Desbiens, a new member of the ADF Product Management team.  I joined Oracle only a few weeks ago. My boss is Grant Ronald, and I have the privilege to work in the same team as Susan Duncan, Frank Nimphius, Lynn Munsinger and Chris Muir. I share with them a passion for all things Java and ADF. With this blog, I hope to help you be more successful with our products – whether you are a customer or a partner. You may have heard of me before. Maybe you have my book in your bookshelf; or maybe we met at a conference. I went to JavaOne, ODTUG Kaleidoscope and Oracle OpenWorld in the past, when I worked for a major consulting firm. I will spare you all the details of my career; you can have a look at my LinkedIn profile if you are curious about my past.  Usually, my posts will be of a technical nature, and will focus on Oracle ADF and Oracle JDeveloper. SOA and portals have always been two topics of interest for me, however, and I will write about them. Over time, you will probably get acquainted with my « strategic » side as well. I devour history books, and always had a tendency to look at the big picture. I will probably not resist to the temptation of mixing IT and history, but this will be occasional, I promise!  At this point, I owe you an explanation about the title of the blog. I am French-Canadian, and wanted to evoke my roots in an obvious yet unobtrusive way. I was born in Chicoutimi, which is one of the main cities found in the Saguenay-Lac-Saint-Jean region. Traditionally, a large part of the wild blueberry production of the province of Québec come from there. A common nickname for the inhabitants is thus Les Bleuets, « The Blueberries » in English. I hope to see you around. You can also follow me on Twitter under  @BlueberryCoder.

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  • Challenge 19 – An Explanation of a Query

    - by Dave Ballantyne
    I have received a number of requests for an explanation of my winning query of TSQL Challenge 19. This involved traversing a hierarchy of employees and rolling a count of orders from subordinates up to superiors. The first concept I shall address is the hierarchyId , which is constructed within the CTE called cteTree.   cteTree is a recursive cte that will expand the parent-child hierarchy of the personnel in the table @emp.  One useful feature with a recursive cte is that data can be ‘passed’ from the parent to the child data.  The hierarchyId column is similar to the hierarchyId data type that was introduced in SQL Server 2008 and represents the position of the person within the organisation. Let us start with a simplistic example Albert manages Bob and Eddie.  Bob manages Carl and Dave. The hierarchyId will represent each person’s position in this relationship in a single field.  In this simple example we could append the userID together into a varchar field as detailed below. This will enable us to select a branch of the tree by filtering using Where hierarchyId  ‘1,2%’ to select Bob and all his subordinates.  Naturally, this is not comprehensive enough to provide a full solution, but as opposed to concatenating the Id’s together into a varchar datatyped column, we can apply the same theory to a varbinary.  By CASTing the ID’s into a datatype of varbinary(4) ,4 is used as 4 bytes of data are used to store an integer and building a hierarchyId  from those.  For example: The important point to bear in mind for later in the query is that the binary data generated is 'byte order comparable'. ie We can ORDER a dataset with it and the resulting data, will be in the order required. Now, would probably be a good time to download the example file and, after the cte ‘cteTree’, uncomment the line ‘select * from cteTree’.  Mark this and all prior code and execute.  This will show you how this theory directly relates to the actual challenge data.  The only deviation from the above, is that instead of using the ID of an employee, I have used the row_number() ranking function to order each level by LastName,Firstname.  This enables me to order by the HierarchyId in the final result set so that the result set is in the required order. Your output should be something like the below.  Notice also the ‘Level’ Column that contains the depth that the employee is within the tree.  I would encourage you to ‘play’ with the query, change the order in the row_number() or the length of the cast in the hierarchyId to see how that effects the outcome.  The next cte, ‘cteTreeWithOrderCount’, is a join between cteTree and the @ord table, and COUNT’s the number of orders per employee.  A LEFT JOIN is employed here to account for the occasion where an employee has made no sales.   Executing a ‘Select * from cteTreeWithOrderCount’ will return the result set as below.  The order here is unimportant as this is only a staging point of the data and only the final result set in a cte chain needs an Order by clause, unless TOP is utilised. cteExplode joins the above result set to the tally table (Nums) for Level Occurances.  So, if level is 2 then 2 rows are required.  This is done to expand the dataset, to create a new column (PathInc), which is the (n+1) integers contained within the heirarchyid.  For example, with the data for Robert King as given above, the below 3 rows will be returned. From this you can see that the pathinc column now contains the values for Andrew Fuller and Steven Buchanan who are Robert King’s superiors within the tree.    Finally cteSumUp, sums the orders for each person and their subordinates using the PathInc generated above, and the final select does the final simple mathematics and filters to restrict the result set to only the ‘original’ row per employee.

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  • SQL SERVER – DMV – sys.dm_os_wait_stats Explanation – Wait Type – Day 3 of 28

    - by pinaldave
    The key Dynamic Management View (DMV) that helps us to understand wait stats is sys.dm_os_wait_stats; this DMV gives us all the information that we need to know regarding wait stats. However, the interpretation is left to us. This is a challenge as understanding wait stats can often be quite tricky. Anyway, we will cover few wait stats in one of the future articles. Today we will go over the basic understanding of the DMV. The Official Book OnLine Reference for DMV is over here: sys.dm_os_wait_stats. I suggest you all to refer this for all the accuracy. Following is a statement from the online book: “Specific types of wait times during query execution can indicate bottlenecks or stall points within the query. Similarly, high wait times, or wait counts server wide can indicate bottlenecks or hot spots in interaction query interactions within the server instance.” This is the statement which has inspired me to write this series. Let us first run the following statement from DMV. SELECT * FROM sys.dm_os_wait_stats ORDER BY wait_time_ms DESC GO Above statement will show us few of the columns. Here it is quick explanation of each of the column. wait_type – this is the name of the wait type. There can be three different kinds of wait types – resource, queue and external. waiting_tasks_count – this incremental counter is a good indication of frequent the wait is happening. If this number is very high, it is good indication for us to investigate that particular wait type. It is quite possible that the wait time is considerably low, but the frequency of the wait is much high. wait_time_ms – this is total wait accumulated for any type of wait. This is the total wait time and includes singal_wait_time_ms. max_wait_time_ms – this indicates the maximum wait type ever occurred for that particular wait type. Using this, one can estimate the intensity of the wait type in past. Again, it is not necessary that this max wait time will occur every time; so do not over invest yourself here. signal_wait_time_ms – this is the wait time when thread is marked as runnable and it gets to the running state. If the runnable queue is very long, you will find that this wait time becomes high. Additionally, please note that this DMV does not show current wait type or wait stats. This is cumulative view of the all the wait stats since server (instance) restarted or wait stats have been cleared. In future blog post, we will also cover two more DMVs which can be helpful to identify wait-related issues. ?sys.dm_os_waiting_tasks sys.dm_exec_requests Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • Explanation needed, for “Ask, don't tell” approach?

    - by the_naive
    I'm taking a course on design patterns in software engineering and here I'm trying to understand the good and the bad way of design relating to "coupling" and "cohesion". I could not understand the concept described in the following image. The example of code shown in the image is ambiguous to me, so I can't quite clearly get what exactly "Ask, don't tell!" approach mean. Could you please explain?

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  • SQL SERVER – Simple Explanation and Puzzle with SOUNDEX Function and DIFFERENCE Function

    - by pinaldave
    Earlier this week I asked a question where I asked how to Swap Values of the column without using CASE Statement. Read here: A Puzzle – Swap Value of Column Without Case Statement,there were more than 50 solutions proposed in the comment. There were many creative solutions. I have mentioned my personal favorite (different ones) here: Solution of Puzzle – Swap Value of Column Without Case Statement. However, I received lots of questions regarding one of the Solution by SIJIN KUMAR V P. He has used the function SOUNDEX in his solution. The request was to explain how SOUNDEX and DIFFERENCE works. Well, there are pretty decent documentations provided over here SOUNDEX function and DIFFERENCE over on MSDN and if I attempt to explain this function I will end up writing the same details which are available on MSDN. Instead of writing theory, we will try to learn this function by using a couple of simple puzzles. You try to solve the puzzles using the MSDN and see if you can learn something very quickly. In simple words - SOUNDEX converts an alphanumeric string to a four-character code to find similar-sounding words or names. The first character of the code is the first character of character_expression and the second through fourth characters of the code are numbers that represent the letters in the expression. Vowels incharacter_expression are ignored unless they are the first letter of the string. DIFFERENCE function returns an integer value. The  integer returned is the number of characters in the SOUNDEX values that are the same. The return value ranges from 0 through 4: 0 indicates weak or no similarity, and 4 indicates strong similarity or the same values. Learning Puzzle 1: Now let us run following four queries and observe its output. SELECT SOUNDEX('SQLAuthority') SdxValue SELECT SOUNDEX('SLTR') SdxValue SELECT SOUNDEX('SaLaTaRa') SdxValue SELECT SOUNDEX('SaLaTaRaM') SdxValue When you look at the result set all the four values are same. The reason for all the values to be same is as for SQL Server SOUNDEX function all the four strings are similarly sounding string. Learning Puzzle 2: Now let us run following five queries and observe its output. SELECT DIFFERENCE (SOUNDEX('SLTR'),SOUNDEX('SQLAuthority')) SELECT DIFFERENCE (SOUNDEX('TH'),SOUNDEX('SQLAuthority')) SELECT DIFFERENCE ('SQLAuthority',SOUNDEX('SQLAuthority')) SELECT DIFFERENCE ('SLTR',SOUNDEX('SQLAuthority')) SELECT DIFFERENCE ('SLTR','SQLAuthority') When you look at the result set you will get the result in the ranges from 1 to 4. Here is how it works if your result is 0 which means absolutely not relevant to each other and if your result is 1 which means the results are relevant to each other. Have you ever used above two functions in your business need or on production server? If yes, would you please leave a comment with use cases. I believe it will be beneficial to everyone. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • need explanation on amortization in algorithm

    - by Pradeep
    I am a learning algorithm analysis and came across a analysis tool for understanding the running time of an algorithm with widely varying performance which is called as amortization. The autor quotes " An array with upper bound of n elements, with a fixed bound N, on it size. Operation clear takes O(n) time, since we should dereference all the elements in the array in order to really empty it. " The above statement is clear and valid. Now consider the next content: "Now consider a series of n operations on an initially empty array. if we take the worst case viewpoint, the running time is O(n^2), since the worst case of a sigle clear operation in the series is O(n) and there may be as many as O(n) clear operations in the series." From the above statement how is the time complexity O(n^2)? I did not understand the logic behind it. if 'n' operations are performed how is it O(n ^2)? Please explain what the autor is trying to convey..

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  • Time passage arithmetic explanation

    - by Cyber Axe
    I ported this from http://www.effectgames.com/effect/article.psp.html/joe/Old_School_Color_Cycling_with_HTML5 some time ago. However i'm now wanting to modify it for the purpose of changing it from floating point to fixed point maths for enhanced efficiency (for those who are going to talk about premature optimization and what not, i want to have my entire engine in fixed point both as a learning process for me and so i can port code more easily to systems in the future that dont have native floating points such as arm cpus) My initial conversion to fixed points just resulted in the cycling stuck on either the first or last frame of cycling. Plus it would be nice to understand better how it works so i can add more options and so forth in the future, my maths however sucks and the comments are limited so i don't really know how the maths work for determining the frame it shoud use (cycleAmount) I was also a beginner when i ported it as i had no idea between floating points and integers and what not. So in summary my question is, can anyone give an explination of the arithmatic used for determining the cycleAmount (which determings the "frame" of the cycle) This is the working floating point maths version of the code: public final void cycle(Colour[] sourceColours, double timeNow, double speedAdjust) { // Cycle all animated colour ranges in palette based on timestamp. sourceColours = sourceColours.clone(); int cycleSize; double cycleRate; double cycleAmount; Cycle cycle; for (int i = 0, len = cycles.length; i < len; ++i) { cycle = cycles[i]; cycleSize = (cycle.HIGH - cycle.LOW) + 1; cycleRate = cycle.RATE / (int) (CYCLE_SPEED / speedAdjust); cycleAmount = 0; if (cycle.REVERSE < 3) { // Standard Cycle cycleAmount = DFLOAT_MOD((timeNow / (1000 / cycleRate)), cycleSize); if (cycle.REVERSE < 1) { cycleAmount = cycleSize - cycleAmount; // If below 1 make sure its not reversed. } } else if (cycle.REVERSE == 3) { // Ping-Pong cycleAmount = DFLOAT_MOD((timeNow / (1000 / cycleRate)), cycleSize << 1); if (cycleAmount >= cycleSize) { cycleAmount = (cycleSize * 2) - cycleAmount; } } else if (cycle.REVERSE < 6) { // Sine Wave cycleAmount = DFLOAT_MOD((timeNow / (1000 / cycleRate)), cycleSize); cycleAmount = Math.sin((cycleAmount * 3.1415926 * 2) / cycleSize) + 1; if (cycle.REVERSE == 4) { cycleAmount *= (cycleSize / 4); } else if (cycle.REVERSE == 5) { cycleAmount *= (cycleSize >> 1); } } if (cycle.REVERSE == 2) { reverseColours(sourceColours, cycle); } if (USE_BLEND_SHIFT) { blendShiftColours(sourceColours, cycle, cycleAmount); } else { shiftColours(sourceColours, cycle, cycleAmount); } if (cycle.REVERSE == 2) { reverseColours(sourceColours, cycle); } } colours = sourceColours; } // This utility function allows for variable precision floating point modulus. private double DFLOAT_MOD(final double d, final double b) { return (Math.floor(d * PRECISION) % Math.floor(b * PRECISION)) / PRECISION; }

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  • Need explanation of hexagonal architecture

    - by Victor Grazi
    I am reading about Alistair Cockburn's Hexagonal Architecture http://alistair.cockburn.us/Hexagonal+architecture with interest. One claim he makes is: "Finally, the automated function regression tests detect any violation of the promise to keep business logic out of the presentation layer. The organization can detect, and then correct, the logic leak." I do not understand this point. Is he saying that because the test is headless, then calls to a ui layer will throw exceptions? That doesn't seem to be a very sound test!

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  • Explanation of the definition of interface inheritance as described in GoF book

    - by Geek
    I am reading the first chapter of the Gof book. Section 1.6 discusses about class vs interface inheritance: Class versus Interface Inheritance It's important to understand the difference between an object's class and its type. An object's class defines how the object is implemented.The class defines the object's internal state and the implementation of its operations.In contrast,an object's type only refers to its interface--the set of requests on which it can respond. An object can have many types, and objects of different classes can have the same type. Of course, there's a close relationship between class and type. Because a class defines the operations an object can perform, it also defines the object's type . When we say that an object is an instance of a class, we imply that the object supports the interface defined by the class. Languages like c++ and Eiffel use classes to specify both an object's type and its implementation. Smalltalk programs do not declare the types of variables; consequently,the compiler does not check that the types of objects assigned to a variable are subtypes of the variable's type. Sending a message requires checking that the class of the receiver implements the message, but it doesn't require checking that the receiver is an instance of a particular class. It's also important to understand the difference between class inheritance and interface inheritance (or subtyping). Class inheritance defines an object's implementation in terms of another object's implementation. In short, it's a mechanism for code and representation sharing. In contrast,interface inheritance(or subtyping) describes when an object can be used in place of another. I am familiar with the Java and JavaScript programming language and not really familiar with either C++ or Smalltalk or Eiffel as mentioned here. So I am trying to map the concepts discussed here to Java's way of doing classes, inheritance and interfaces. This is how I think of of these concepts in Java: In Java a class is always a blueprint for the objects it produces and what interface(as in "set of all possible requests that the object can respond to") an object of that class possess is defined during compilation stage only because the class of the object would have implemented those interfaces. The requests that an object of that class can respond to is the set of all the methods that are in the class(including those implemented for the interfaces that this class implements). My specific questions are: Am I right in saying that Java's way is more similar to C++ as described in the third paragraph. I do not understand what is meant by interface inheritance in the last paragraph. In Java interface inheritance is one interface extending from another interface. But I think the word interface has some other overloaded meaning here. Can some one provide an example in Java of what is meant by interface inheritance here so that I understand it better?

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  • Explanation on how "Tell, Don't Ask" is considered good OO

    - by Pubby
    This blogpost was posted on Hacker News with several upvotes. Coming from C++, most of these examples seem to go against what I've been taught. Such as example #2: Bad: def check_for_overheating(system_monitor) if system_monitor.temperature > 100 system_monitor.sound_alarms end end versus good: system_monitor.check_for_overheating class SystemMonitor def check_for_overheating if temperature > 100 sound_alarms end end end The advice in C++ is that you should prefer free functions instead of member functions as they increase encapsulation. Both of these are identical semantically, so why prefer the choice that has access to more state? Example 4: Bad: def street_name(user) if user.address user.address.street_name else 'No street name on file' end end versus good: def street_name(user) user.address.street_name end class User def address @address || NullAddress.new end end class NullAddress def street_name 'No street name on file' end end Why is it the responsibility of User to format an unrelated error string? What if I want to do something besides print 'No street name on file' if it has no street? What if the street is named the same thing? Could someone enlighten me on the "Tell, Don't Ask" advantages and rationale? I am not looking for which is better, but instead trying to understand the author's viewpoint.

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  • SQL SERVER – SSAS – Multidimensional Space Terms and Explanation

    - by pinaldave
    I was presenting on SQL Server session at one of the Tech Ed On Road event in India. I was asked very interesting question during ‘Stump the Speaker‘ session. I am sharing the same with all of you over here. Question: Can you tell me in simple words what is dimension, member and other terms of multidimensional space? There is no simple example for it. This is extreme fundamental question if you know Analysis Service. Those who have no exposure to the same and have not yet started on this subject, may find it a bit difficult. I really liked his question so I decided to answer him there as well blog about the same over here. Answer: Here are the most important terms of multidimensional space – dimension, member, value, attribute and size. Dimension – It describes the point of interests for analysis. Member – It is one of the point of interests in the dimension. Value – It uniquely describes the member. Attribute – It is collection of multiple members. Size – It is total numbers for any dimension. Let us understand this further detail taking example of any space. I am going to take example of distance as a space in our example. Dimension – Distance is a dimension for us. Member – Kilometer – We can measure distance in Kilometer. Value – 4 – We can measure distance in the kilometer unit and the value of the unit can be 4. Attribute – Kilometer, Miles, Meter – The complete set of members is called attribute. Size – 100 KM – The maximum size decided for the dimension is called size. The same example can be also defined by using time space. Here is the example using time space. Dimension – Time Member – Date Value – 25 Attribute – 1, 2, 3…31 Size – 31 I hope it is clear enough that what are various multidimensional space and its terms. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Business Intelligence, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • How to explain OOP to a matlab programmer?

    - by Oak
    I have a lot of friends who come from electrical / physical / mechanical engineering background, and are curious about what is "OOP" all about. They all know Matlab quite well, so they do have basic programming background; but they have a very hard time grasping a complex type system which can benefit from the concepts OOP introduces. Can anyone propose a way I can try to explain it to them? I'm just not familiar with Matlab myself, so I'm having troubles finding parallels. I think using simple examples like shapes or animals is a bit too abstract for those engineers. So far I've tried using a Matrix interface vs array-based / sparse / whatever implementations, but that didn't work so well, probably because different matrix types are already well-supported in Matlab.

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  • looking for a short explanation of fuzzy logic

    - by user613326
    Well i got the idea that basics of fuzzy logic are not that hard to grasp. And i got the feeling that someone might explain it to me in like 30 minutes. Just like i understand neural networks and am able to re-create the famous Xor problem. And go just beyond it and create 3 layer networks of x nodes. I'd like to understand fuzzy till a similar usefully level, in c# language. However the problem is face, I'd like to get concept right however i see many websites who include lots of errors in their basic explaining. Like for example showing pictures and use different numbers as shown in pictures to calculate, as if lots of people just copied stuff without noticing what they write down. While others for me go to deep in their math notation) To me that's very annoying to learn from. For me there is no need to re-invent wheel; Aforge already got a fuzzy logic framework. So what i am looking for are some good examples, good examples like how the neural XOR problem is solved. Is there anyone such a instructional resource out there; do you know a web page, or YouTube where it is shortly explained, what would you recommend me ? Note this article comes close; but it just doesnt nail it for me. After that i downloaded a bunch of free PDF's but most are academic and hard to read for me (i'm not English and dont have a special math degree). (i've been looking around a lot for this, good starter material about it is hard to find).

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  • 'dock' working in simple words

    - by Shirish11
    I would like to know the idea behind the working of 'docking' in applications. I have worked with applications where components from individual forms are docked on a single main form to provide the necessary GUI. But I don't have any idea whats happening in the background. According to Wikipedia A dock is a graphical user interface element that typically provides the user with a way of launching, switching between, and monitoring running programs or applications. Now I am a bit confused if it is some component or an event or a property or something else. EDIT : The applications was developed in Delphi on windows platform. There is something more in Delphi (manual dock and automatic dock).

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  • A Laymans Explanation of The Derivatives Market and Crash

      This was passed on to me by a good friend, and I found the analogy so compelling that I decided to share it: Heidi is the proprietor of a bar in Detroit . She realizes that virtually all of her customers  are unemployed alcoholics and, as such, can no longer afford to patronize her bar. To solve this problem, she comes up with new marketing plan that allows her customers to drink now, but pay later. She keeps track of the drinks consumed on a ledger (thereby granting the customers...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • What is the benefit of writing to a temp location, And then copying it to the intended destination?

    - by Devdatta Tengshe
    I am writing an application that works with satellite Images, and my boss asked me to look at some of the commercial application, and see how they behave. I found a strange behavior and then as I was looking, I found it in other standard applications as well. These Programs first write to the temp folder, and then copy it to the intended destination. Example: 7zip first extracts to the temp folder, and then copies the extracted data to the location that you had asked it to extract the data to. I see several problems with this approach: 1.The temp folder might not have enough space, while the intended location might have that much space. 2.If it is a large file, it can take a non-negligible amount of time for the copy operation. I thought about it a lot, but I couldn't see one single positive point to doing this. Am I missing something, or is there a real benefit to doing this?

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