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• Need help with WCF design

  - by Jason

  I have been tasked with creating a set of web services. We are a Microsoft shop, so I will be using WCF for this project. There is an interesting design consideration that I haven't been able to figure out a solution for yet. I'll try to explain it with an example: My WCF service exposes a method named Foo(). 10 different users call Foo() at roughly the same time. I have 5 special resources called R1, R2, R3, R4, and R5. We don't really need to know what the resource is, other than the fact that a particular resource can only be in use by one caller at a time. Foo() is responsible to performing an action using one of these special resources. So, in a round-robin fashion, Foo() needs to find a resource that is not in use. If no resources are available, it must wait for one to be freed up. At first, this seems like an easy task. I could maybe create a singleton that keeps track of which resources are currently in use. The big problem is the fact that I need this solution to be viable in a web farm scenario. I'm sure there is a good solution to this problem, but I've just never run across this scenario before. I need some sort of resource tracker / provider that can be shared between multiple WCF hosts. Any ideas from the architects out there would be greatly appreciated!

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• How is conversion of float/double to int handled in printf?

  - by Sandip

  Consider this program int main() { float f = 11.22; double d = 44.55; int i,j; i = f; //cast float to int j = d; //cast double to int printf("i = %d, j = %d, f = %d, d = %d", i,j,f,d); //This prints the following: // i = 11, j = 44, f = -536870912, d = 1076261027 return 0; } Can someone explain why the casting from double/float to int works correctly in the first case, and does not work when done in printf? This program was compiled on gcc-4.1.2 on 32-bit linux machine. EDIT: Zach's answer seems logical, i.e. use of format specifiers to figure out what to pop off the stack. However then consider this follow up question: int main() { char c = 'd'; // sizeof c is 1, however sizeof character literal // 'd' is equal to sizeof(int) in ANSI C printf("lit = %c, lit = %d , c = %c, c = %d", 'd', 'd', c, c); //this prints: lit = d, lit = 100 , c = d, c = 100 //how does printf here pop off the right number of bytes even when //the size represented by format specifiers doesn't actually match //the size of the passed arguments(char(1 byte) & char_literal(4 bytes)) return 0; } How does this work?

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• Linear feedback shift register?

  - by Mattia Gobbi

  Lately I bumped repeatedly into the concept of LFSR, that I find quite interesting because of its links with different fields and also fascinating in itself. It took me some effort to understand, the final help was this really good page, much better than the (at first) cryptic wikipedia entry. So I wanted to write some small code for a program that worked like a LFSR. To be more precise, that somehow showed how a LFSR works. Here's the cleanest thing I could come up with after some lenghtier attempts (Python): def lfsr(seed, taps): sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor sr, xor = str(xor) + sr[:-1], 0 print sr if sr == seed: break lfsr('11001001', (8,7,6,1)) #example I named "xor" the output of the XOR function, not very correct. However, this is just meant to show how it circles through its possible states, in fact you noticed the register is represented by a string. Not much logical coherence. This can be easily turned into a nice toy you can watch for hours (at least I could :-) def lfsr(seed, taps): import time sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor print time.sleep(0.75) sr, xor = str(xor) + sr[:-1], 0 print sr print time.sleep(0.75) Then it struck me, what use is this in writing software? I heard it can generate random numbers; is it true? how? So, it would be nice if someone could: explain how to use such a device in software development come up with some code, to support the point above or just like mine to show different ways to do it, in any language Also, as theres not much didactic stuff around about this piece of logic and digital circuitry, it would be nice if this could be a place for noobies (like me) to get a better understanding of this thing, or better, to understand what it is and how it can be useful when writing software. Should have made it a community wiki? That said, if someone feels like golfing... you're welcome.

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• passing an array of structures (containing two mpz_t numbers) to a function

  - by jerome

  Hello, I'm working on some project where I use the type mpz_t from the GMP C library. I have some problems passing an array of structures (containing mpz_ts) adress to a function : I wille try to explain my problem with some code. So here is the structure : struct mpz_t2{ mpz_t a; mpz_t b; }; typedef struct mpz_t2 *mpz_t2; void petit_test(mpz_t2 *test[]) { printf("entering petit test function\n"); for (int i=0; i < 4; i++) { gmp_printf("test[%d]->a = %Zd and test[%d]->b = %Zd\n", test[i]->a, test[i]->b); } } /* IN MAIN FUNCTION */ mpz_t2 *test = malloc(4 * sizeof(mpz_t2 *)); for (int i=0; i < 4; i++) { mpz_t2_init(&test[i]); // if I pass test[i] : compiler error mpz_set_ui(test[i].a, i); //if test[i]->a compiler error mpz_set_ui(test[i].b, i*10); //same problem gmp_printf("%Zd\n", test[i].b); //prints correct result } petit_test(test); The programm prints the expected result (in main) but after entering the petit_test function produces a segmentation fault error. I would need to edit the mpz_t2 structure array in petit_test. I tried some other ways allocating and passing the array to the function but I didn't manage to get this right. If someone has a solution to this problem, I would be very thankfull! Regards, jérôme.

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• JS Object this.method() breaks via jQuery

  - by Peter Boughton

  I'm sure there's a simple answer to this, but it's Friday afternoon and I'm tired. :( Not sure how to explain it, so I'll just go ahead and post example code... Here is a simple object: var Bob = { Stuff : '' , init : function() { this.Stuff = arguments[0] } , doSomething : function() { console.log( this.Stuff ); } } And here it is being used: $j = jQuery.noConflict(); $j(document).ready( init ); function init() { Bob.init('hello'); Bob.doSomething(); $j('#MyButton').click( Bob.doSomething ); } Everything works, except for the last line. When jQuery calls the doSomething method it is overriding 'this' and stopping it from working. Trying to use just Stuff doesn't work either. So how do I refer to an object's own properties in a way that allows jQuery to call it, and also allows the object to work with the calling jQuery object? i.e. I would like to be able to do things like this: doSomething : function() { console.log( <CurrentObject>.Stuff + $j(<CallerElement>).attr('id') ); } (Where <CurrentObject> and <CallerElement> are replaced with appropriate names.)

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• Model login constraints based on time

  - by DaDaDom

  Good morning, for an existing web application I need to implement "time based login constraints". It means that for each user, later maybe each group, I can define timeslots when they are (not) allowed to log in into the system. As all data for the application is stored in database tables, I need to somehow create a way to model this idea in that way. My first approach, I will try to explain it here: Create a tree of login constraints (called "timeslots") with the main "categories", like "workday", "weekend", "public holiday", etc. on the top level, which are in a "sorted" order (meaning "public holiday" has a higher priority than "weekday") for each top level node create subnodes, which have a finer timespan, like "monday", "tuesday", ... below that, create an "hour" level: 0, 1, 2, ..., 23. No further details are necessary. set every member to "allowed" by default For every member of the system create a 1:n relationship member:timeslots which defines constraints, e.g. a member A may have A:monday-forbidden and A:tuesday-forbidden Do a depth-first search at every login and check if the member has a constraint. Why a depth first search? Well, I thought that it may be that a member has the rules: A:monday->forbidden, A:monday-10->allowed, A:mondey-11->allowed So a login on monday at 12:30 would fail, but one at 10:30 succeed. For performance reasons I could break the relational database paradigm and set a flag for every entry in the member-to-timeslots-table which is set to true if the member has information set for "finer" timeslots, but that's a second step. Is this model in principle a good idea? Are there existing models? Thanks.

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• Login for webapp, needs to be availible for supportstaff

  - by Christian W

  I know the title is a little off, but it's hard to explain the problem in a short sentence. I am the administrator of a legacy webapp that lets users create surveys and distribute them to a group of people. We have two kinds of "users". 1. Authorized licenseholders which does all setup themselves. 2. Clients who just want to have a survey run, but still need a user (because the webapp has "User" as the top entity in a surveyenvironment.) Sometimes users in #1 want's us to do the setup for them (which we offer to do). This means that we have to login as them. This is also how we do support, we login as them and then follow them along, guiding them. Which brings me to my dilemma. Currently our security is below par. But this makes it simple for us to do support. We do want to increase our security, and one thing I have been considering is just doing the normal hashing to DB, however, we need to be able to login as a customer, and if they change their password without telling us, and the password is hashed in the db, we have no way of knowing it. So I was thinking of some kind of twoway encryption for the passwords. Either that or some kind of master password. Any suggestions? (The platform is classic ASP... I said it was legacy...)

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• How to use void*

  - by Rondogiannis Aristophanes

  I am imlementing a simple merge function and I have got stuck, as the compiler gives me errors that I cannot explain. Here is my merge function: void merge(void *a, int beg, int middle, int end, int (*cmp)(const void*, const void* { std::stack<void*> first; std::stack<void*> second; for(int i = beg; i < middle; i++) { first.push(a+i); } for(int i = middle; i < end; i++) { second.push(a+i); } for(int i = beg; i < end; i++) { if(first.empty()) { void *tmp = second.top(); second.pop(); a+i = tmp; } else if(second.empty()) { void *tmp = first.top(); first.pop(); a+i = tmp; } else if(cmp(first.top(), second.top())) { void *tmp = first.top(); first.pop(); a+i = tmp; } else { void *tmp = second.top(); second.pop(); a+i = tmp; } } } And here is the error: sort.h: In function `void merge(void*, int, int, int, int (*)(const void*, const void*))': sort.h:9: error: pointer of type `void *' used in arithmetic sort.h:12: error: pointer of type `void *' used in arithmetic sort.h:19: error: pointer of type `void *' used in arithmetic sort.h:19: error: non-lvalue in assignment sort.h:23: error: pointer of type `void *' used in arithmetic sort.h:23: error: non-lvalue in assignment sort.h:27: error: pointer of type `void *' used in arithmetic sort.h:27: error: non-lvalue in assignment sort.h:31: error: pointer of type `void *' used in arithmetic sort.h:31: error: non-lvalue in assignment Can anyone help me? TIA.

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• Why does autoboxing in Java allow me to have 3 possible values for a boolean?

  - by John

  Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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• MySQL Query That Can Pull the Data I am Seeking?

  - by Amy

  On the project I am working on, I am stuck with the table structure from Hades. Two things to keep in mind: I can't change the table structure right now. I'm stuck with it for the time being. The queries are dynamically generated and not hard coded. So, while I am asking for a query that can pull this data, what I am really working toward is an algorithm that will generate the query I need. Hopefully, I can explain the problem without making your eyes glaze over and your brain implode. We have an instance table that looks (simplified) along these lines: Instances InstanceID active 1 Y 2 Y 3 Y 4 N 5 Y 6 Y Then, there are multiple data tables along these lines: Table1 InstanceID field1 reference_field2 1 John 5 2 Sally NULL 3 Fred 6 4 Joe NULL Table2 InstanceID field3 5 1 6 1 Table3 InstanceID fieldID field4 5 1 Howard 5 2 James 6 2 Betty Please note that reference_field2 in Table1 contains a reference to another instance. Field3 in Table2 is a bit more complicated. It contains a fieldID for Table 3. What I need is a query that will get me a list as follows: InstanceID field1 field4 1 John Howard 2 Sally 3 Fred The problem is, in the query I currently have, I do not get Fred because there is no entry in Table3 for fieldID 1 and InstanceID 6. So, the very best list I have been able to get thus far is InstanceID field1 field4 1 John Howard 2 Sally In essence, if there is an entry in Table1 for Field 2, and there is not an entry in Table 3 that has the instanceID contained in field2 and the field ID contained in field3, I don't get the data from field1. I have looked at joins till I'm blue in the face, and I can't see a way to handle the case when table3 has no entry.

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• multiple redirect??

  - by Ryan Pitts

  Ok, i won't go into the full details (too much to explain) but here is what i am trying to do. I have a button on a webpage (we'll call page-1) that links to a page (we'll call it page-2). This page opens in the same window. However, i need the page (page-2) that opens to open up a new window with another page (we'll call this one page-3) when it loads. So virtually when you click the initial button (on page-1) it will go to a new page (page-2) AND a window will open as well with a different page (page-3). This is where it gets tricky. I need page-2 to automatically redirect back to page-1 after it launches page-3. Is this possible and if so, how?? Could it be a JQuery thing? Please just give some answers...i know this is way crazy and a huge workaround - but this is my last resort for this particular website. I have to do it this way because of the lack of control over some of the code.

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• Binder and variadic template ends up in a segmentation fault

  - by phlipsy

  I wrote the following program #include <iostream> template<typename C, typename Res, typename... Args> class bind_class_t { private: Res (C::*f)(Args...); C *c; public: bind_class_t(Res (C::*f)(Args...), C* c) : f(f), c(c) { } Res operator() (Args... args) { return (c->*f)(args...); } }; template<typename C, typename Res, typename... Args> bind_class_t<C, Res, Args...> bind_class(Res (C::*f)(Args...), C* c) { return bind_class<C, Res, Args...>(f, c); } class test { public: int add(int x, int y) { return x + y; } }; int main() { test t; // bind_class_t<test, int, int, int> b(&test::add, &t); bind_class_t<test, int, int, int> b = bind_class(&test::add, &t); std::cout << b(1, 2) << std::endl; return 0; } compiled it with gcc 4.3.3 and got a segmentation fault. After spending some time with gdb and this program it seems to me that the addresses of the function and the class are mixed up and a call of the data address of the class isn't allowed. Moreover if I use the commented line instead everything works fine. Can anyone else reproduce this behavior and/or explain me what's going wrong here?

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• Obtaining YouTube video ID in a URL and inputting selected video ID into a URL

  - by Dave

  I've been having trouble in trying to figure this out. What I am trying to do is, obtain the ID of a video from YouTube, and input the 11 character ID into the css of a div of a specific id by using jquery. I know the URL for the thumbnail of any video, but I just need to be able to change the ID to display different video thumbnails. <script> $(document).ready(function() { function(data){ videoID = data.split('www.youtube.com/v/')[1].split('&amp')[0]; $("#304817679").append(videoID); }); $("#304817679").replaceWith("<div id=\"304817679\" style=\"background: url(http://img.youtube.com/vi/"+ $.function(data) +"/0.jpg) no-repeat middle; width: 15px; height: 150px;\"></div>"); }); }); </script> <div id="304817679"> <div style="display: none;"><object width="248" height="222"><param name="movie" value="http://www.youtube.com/v/vy90n2nNRKQ&amp;rel=0&amp;egm=0&amp;showinfo=0&amp;fs=1"></param><param name="wmode" value="transparent"></param><param name="allowFullScreen" value="true"></param><embed src="http://www.youtube.com/v/vy90n2nNRKQ&amp;rel=0&amp;egm=0&amp;showinfo=0&amp;fs=1" type="application/x-shockwave-flash" width="248" height="222" allowFullScreen="true" wmode="transparent"></embed></object></div> </div> Trying to explain this better, I want the 11 Character YouTube Video ID from the embedded code, and put it into the URL of the thumbnail (http://img.youtube.com/vi/"+ function(data) +"/0.jpg). Which, would then also replace the original div (div id="304817679"). Am I on the right track with my script? I'm entirely new to this, and I would appreciate some of the help that's offered here.

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• SSH traffic over openvpn freezes under weird circumstances

  - by user289581

  I have an openvpn (version 2.1_rc15 at both ends) connection setup between two gentoo boxes using shared keys. it works fine for the most part. I use mysql, http, ftp, scp over the vpn with no problems. But when I ssh from the client to the server over the vpn, weird things happen. I can login, i can execute some commands. But if i try to run an ncurses application like top, or i try to cat a file, the connection will stall and I'll have to sever the ssh session. I can, for example, execute "echo blah; echo .; echo blah" and it will output the three lines of text over the ssh session fine. But if i execute "cat /etc/motd" the session will freeze the moment I press enter. While it seems like a terminal emulation problem it makes no sense why using the vpn would affect the ability for ssh to render things correctly. I am at a loss to explain why everything else works, including scp, but ssh just breaks over the vpn. Any thoughts ?

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• Umbraco template issues

  - by bomortensen

  Hi fellow Umbraco users, I'm currently building my first umbraco website and since I'm completely new to umbraco I've already ran into a problem which I'm sure is pretty straight-forward to do. That said, I'm by no means a beginner when it comes to building sites that run on a (open source) CMS as I've been using Joomla! since it was called Mambo. Anyway, the site I'm building is here: my site What I want to do is to have some content in the white box that changes when you mouseover/hover one of the menu items. Also that content has to stay "active" when you've clicked on a link (i.e. if you click on "Profile" I need to highlight the Profile menu item with the gray color and the white boxs content needs to be what would be related to the Profile menu item. How do I go about this? What would be the best practice when it comes to showing multiple content on a site? I've watched the video about multiple Content Place Holders, but I never really got it to work. I can't get a page to display in the NavigationPlaceHolder (the placeholder I put in the white box), but thats because the actual page is Frontpage.aspx and not WhateverIsInThenavigationPlaceHolder.aspx. If I go to the mysite.dk/WhateverIsInTheNavigationPlaceHolder.aspx it shows up fine. What have I missed here? :) Thanks in advance! If my question is not clear in some ways, please tell me and I will try to explain it better. All the best, Bo

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• MySQL: order by and limit gives wrong result

  - by Larry K

  MySQL ver 5.1.26 I'm getting the wrong result with a select that has where, order by and limit clauses. It's only a problem when the order by uses the id column. I saw the MySQL manual for LIMIT Optimization My guess from reading the manual is that there is some problem with the index on the primary key, id. But I don't know where I should go from here... Question: what should I do to best solve the problem? Works correctly: mysql> SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY id DESC ; +------+---------------------+ | id | created_at | +------+---------------------+ | 1336 | 2010-05-14 08:05:25 | | 1334 | 2010-05-06 08:05:25 | | 1331 | 2010-05-05 23:18:11 | +------+---------------------+ 3 rows in set (0.00 sec) WRONG result when limit added! Should be the first row, id - 1336 mysql> SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY id DESC limit 1; +------+---------------------+ | id | created_at | +------+---------------------+ | 1331 | 2010-05-05 23:18:11 | +------+---------------------+ 1 row in set (0.00 sec) Works correctly: mysql> SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY created_at DESC ; +------+---------------------+ | id | created_at | +------+---------------------+ | 1336 | 2010-05-14 08:05:25 | | 1334 | 2010-05-06 08:05:25 | | 1331 | 2010-05-05 23:18:11 | +------+---------------------+ 3 rows in set (0.01 sec) Works correctly with limit: mysql> SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY created_at DESC limit 1; +------+---------------------+ | id | created_at | +------+---------------------+ | 1336 | 2010-05-14 08:05:25 | +------+---------------------+ 1 row in set (0.01 sec) Additional info: explain SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY id DESC limit 1; +----+-------------+------------------+-------+--------------------------------------+--------------------------------------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------------+-------+--------------------------------------+--------------------------------------+---------+------+------+-------------+ | 1 | SIMPLE | billing_invoices | range | index_billing_invoices_on_account_id | index_billing_invoices_on_account_id | 4 | NULL | 3 | Using where | +----+-------------+------------------+-------+--------------------------------------+--------------------------------------+---------+------+------+-------------+

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• At what line in the following code should I be commiting my UnitOfWork ?

  - by Pure.Krome

  Hi folks, I have the following code which is in a transaction. I'm not sure where/when i should be commiting my unit of work. If someone knows where, can they please explain WHY they have said, where? (i'm trying to understand the pattern through example(s), as opposed to just getting my code to work). Here's what i've got :- using (TransactionScope transactionScope = new TransactionScope(TransactionScopeOption.RequiresNew, new TransactionOptions { IsolationLevel = IsolationLevel.ReadUncommitted })) { _logEntryRepository.InsertOrUpdate(logEntry); //_unitOfWork.Commit(); // Here, commit #1 ? // Now, if this log entry was a NewConnection or an LostConnection, then we need to make sure we update the ConnectedClients. if (logEntry.EventType == EventType.NewConnection) { _connectedClientRepository.Insert(new ConnectedClient { LogEntryId = logEntry.LogEntryId }); //_unitOfWork.Commit(); // Here, commit #2 ? } // A (PB) BanKick does _NOT_ register a lost connection .. so we need to make sure we handle those scenario's as a LostConnection. if (logEntry.EventType == EventType.LostConnection || logEntry.EventType == EventType.BanKick) { _connectedClientRepository.Delete(logEntry.ClientName, logEntry.ClientIpAndPort); //_unitOfWork.Commit(); // Here, commit #3 ? } _unitOfWork.Commit(); // Here, commit #4 ? transactionScope.Complete(); } Cheers :)

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• Could Python's logging SMTP Handler be freezing my thread for 2 minutes?

  - by Oddthinking

  A rather confusing sequence of events happened, according to my log-file, and I am about to put a lot of the blame on the Python logger, which is a bold claim. I thought I should get some second opinions about whether what I am saying could be true. I am trying to explain why there is are several large gaps in my log file (around two minutes at a time) during stressful periods for my application when it is missing deadlines. I am using Python's logging module on a remote server, and have set-up, with a configuration file, for all logs of severity of ERROR or higher to be emailed to me. Typically, only one error will be sent at a time, but during periods of sustained problems, I might get a dozen in a minute - annoying, but nothing that should stress SMTP. I believe that, after a short spurt of such messages, the Python logging system (or perhaps the SMTP system it is sitting on) is encountering errors or congestion. The call to Python's log is then BLOCKING for two minutes, causing my thread to miss its deadlines. (I was smart enough to move the logging until after the critical path of the application - so I don't care if logging takes me a few seconds, but two minutes is far too long.) This seems like a rather awkward architecture (for both a logging system that can freeze up, and for an SMTP system (Ubuntu, sendmail) that cannot handle dozens of emails in a minute**), so this surprises me, but it exactly fits the symptoms. Has anyone had any experience with this? Can anyone describe how to stop it from blocking? ** EDIT: I actually counted. A little under 4000 short emails in two hours. So far more than I suggested, sorry. But enough to over-fill a Sendmail's buffers?

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• How can I search an XML file without a dynamic language?

  - by jeph perro

  Let me try to explain my situation: We are using a CMS which 'bakes' a website, and you publish it to a webserver. The published site contains only static HTML ( or XML ) pages ( generated from the content in the CMS database ). I imported an XML file with the names and phone numbers from the company phone directory. Using only XSLT, can I create a way to search that directory? For example, if my XML file, directory.xml looks like this: <directory> <person> <fname>Ryan</fname> <lname>Purple</lname> <phone>887 778 5544</phone> </person> <person> <fname>Tanya</fname> <lname>Orange</lname> <phone>887 998 5541</phone> </person> <directory> Can I create a way to search for a person with the last name starting with "Pur" ? Can I pass a parameter to the XSLT? Can I search the XML tree to match the string in the parameter?

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• Properties vs. Fields: Need help grasping the uses of Properties over Fields.

  - by pghtech

  First off, I have read through a list of postings on this topic and I don't feel I have grasped properties because of what I had come to understand about encapsulation and field modifiers (private, public..ect). One of the main aspects of C# that I have come to learn is the importance of data protection within your code by the use of encapsulation. I 'thought' I understood that to be because of the ability of the use of the modifiers (private, public, internal, protected). However, after learning about properties I am sort of torn in understanding not only properties uses, but the overall importance/ability of data protection (what I understood as encapsulation) within C#. To be more specific, everything I have read when I got to properties in C# is that you should try to use them in place of fields when you can because of: 1) they allow you to change the data type when you can't when directly accessing the field directly. 2) they add a level of protection to data access However, from what I 'thought' I had come to know about the use of field modifiers did #2, it seemed to me that properties just generated additional code unless you had some reason to change the type (#1) - because you are (more or less) creating hidden methods to access fields as opposed to directly. Then there is the whole modifiers being able to be added to Properties which further complicates my understanding for the need of properties to access data. I have read a number of chapters from different writers on "properties" and none have really explained a good understanding of properties vs. fields vs. encapsulation (and good programming methods). Can someone explain: 1) why I would want to use properties instead of fields (especially when it appears I am just adding additional code 2) any tips on recognizing the use of properties and not seeing them as simply methods (with the exception of the get;set being apparent) when tracing other peoples code? 3) Any general rules of thumb when it comes to good programming methods in relation to when to use what? Thanks and sorry for the long post - I didn't want to just ask a question that has been asked 100x without explaining why I am asking it again.

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• Google Maps openInfoWindowHTML array problem

  - by user188791

  Could someone please help explain why I can't get this to work? I properly generates all the locations, however, it doesn't generate the info boxes. Why is this and can someone help me with it? var map = new GMap2(document.getElementById("map")); map.addControl(new GSmallMapControl()); map.addControl(new GMapTypeControl()); map.setCenter(new GLatLng(47.6062, -122.3321), 8); var wa_locations = new Array(new Array("Seattle", "47.6062", "-122.3321", "###-###-####", "###-###-####"), new Array("Bellevue", "47.6104", "-122.2007", "###-###-####", "###-###-####"), new Array("Tacoma", "47.2529", "-122.4443", "###-###-####", "###-###-####"), new Array("Everett", "47.9790", "-122.2021", "###-###-####", "###-###-####")); for(var i = 0; i < wa_locations.length; i++) { var point = new GLatLng(wa_locations[i][1], wa_locations[i][2]); map.addOverlay(new GMarker(point)); GEvent.addListener(point, "click", function() { point.openInfoWindowHtml("<b>" + wa_locations[i][0] + "</b><br/>Sales: " + wa_locations[i][3] + "<br/>Helpdesk: " + wa_locations[i][4] + ""); }); }

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• Does Github.com have to create a merge commit when you merge from a fork ?

  - by Nishant

  I cloned the master and started doing he my work . Due to permissions I push the branch to my fork . I then sent a pull request to my master and someone with permission does the merge . I notice that Github.com creates a merge commit snapshot which to me looks like just a diff of the entire changes which is actually not necessary but helpful in the sense I can just look at merge commit to see the entire diff . I can see the same sha has as my own branch - hence it looks like the merge is an extra commit which probably aint nexeccary since its a fast forward ? master - a myfork(computer) - a->b->c myfork(github) - a->b->c Pull request myfork - master (which it says I can automatically merge) shows the entire diff and then when I merge it , it shows up as master - a->b->c-d . The d is a merge commit which I think it not really required because it is a fast forward ? Can someone explain why does this happen ? I think this is the same scenario if I rebase master if master had gone ahead , but that has not happened . Master is still at when I merge .

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• Testing performance of queries in mysl

  - by Unreason

  I am trying to setup a script that would test performance of queries on a development mysql server. Here are more details: I have root access I am the only user accessing the server Mostly interested in InnoDB performance The queries I am optimizing are mostly search queries (SELECT ... LIKE '%xy%') What I want to do is to create reliable testing environment for measuring the speed of a single query, free from dependencies on other variables. Till now I have been using SQL_NO_CACHE, but sometimes the results of such tests also show caching behaviour - taking much longer to execute on the first run and taking less time on subsequent runs. If someone can explain this behaviour in full detail I might stick to using SQL_NO_CACHE; I do believe that it might be due to file system cache and/or caching of indexes used to execute the query, as this post explains. It is not clear to me when Buffer Pool and Key Buffer get invalidated or how they might interfere with testing. So, short of restarting mysql server, how would you recommend to setup an environment that would be reliable in determining if one query performs better then the other?

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• Putting BigDecimal data into HSQLDB test database using DbUnit

  - by Denise

  Hi everyone, I'm using Hibernate JPA in my backend. I am writing a unit test using JUnit and DBUnit to insert a set of data into an in-memory HSQL database. My dataset contains: <order_line order_line_id="1" quantity="2" discount_price="0.3"/> Which maps to an OrderLine Java object where the discount_price column is defined as: @Column(name = "discount_price", precision = 12, scale = 2) private BigDecimal discountPrice; However, when I run my test case and assert that the discount price returned equals 0.3, the assertion fails and says that the stored value is 0. If I change the discount_price in the dataset to be 0.9, it rounds up to 1. I've checked to make sure HSQLDB isn't doing the rounding and it definitely isn't because I can insert an order line object using Java code with a value like 5.3 and it works fine. To me, it seems like DBUtils is for some reason rounding the number I've defined. Is there a way I can force this to not happen? Can anyone explain why it might be doing this? Thanks!

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• python VTE Terminal weirdness

  - by mykhal

  i'm trying to use the terminal from python VTE binding (python-vte from debian squeeze) as a virtual terminal emulator (just for ANSI/control chars text processing) in interactive python console, everything looks (almost) all right: >>> import vte >>> term = vte.Terminal() >>> term.feed("a\nb") >>> print repr(term.get_text(lambda *a: True).rstrip()) 'a\n b' however, launching this code (little modified) as python script, different result is yielded: $ python vte_wiredness_1.py '' strangely enough, pasting the code back into the (new) interactive python session also yields empty string: >>> import vte >>> term = vte.Terminal() >>> term.feed("a\nb") >>> print repr(term.get_text(lambda *a: True).rstrip()) '' >>> first thing caming on my mind was that the only difference between the two cases is the timing - there had to be some delay before get_text. unfortunately, preluding get_text with some seconds sleep did not help then i thought it has something to do with X window environment. but the results are the same pure linux console (with some warning on missing graphics). i wonder what causes such an unpredictable behavior (interactive console - pasted vs typed, and it's not the delay.. ant the interactive console has nothing to do with the vte terminal object.. i guess) can someone explain what is happening? is it possible to use the VTE Term such way? that the "b" letter in the output is preceded by the space, is another strangeness (all consecutive lines are preceded by more spaces.. looks like I have to send carriage return before the string.) (the lambda *a: True get_text method argument i'm using is a dummy callback, it's is some SlotSelectedCallback.. for its explanation i'd be grateful as well :) )

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