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• Best Way to Generate Unique and consecutives numbers in Oracle

  - by RRUZ

  I need to generate unique and consecutive numbers (for use on an invoice), in a fast and reliable way. currently use a Oracle sequence, but in some cases generated numbers are not consecutive because of exceptions that may occur. I thought a couple of solutions to manage this problem, but neither of they convincing me. What solution do you recommend? Use a select max () SELECT MAX (NVL (doc_num, 0)) +1 FROM invoices Use a table to store the last number generated for the invoice. UPDATE docs_numbers SET last_invoice = last_invoice + 1 Another Solution?

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• Simulating C-style for loops in python

  - by YGA

  (even the title of this is going to cause flames, I realize) Python made the deliberate design choice to have the for loop use explicit iterables, with the benefit of considerably simplified code in most cases. However, sometimes it is quite a pain to construct an iterable if your test case and update function are complicated, and so I find myself writing the following while loops: val = START_VAL while <awkward/complicated test case>: # do stuff ... val = <awkward/complicated update> The problem with this is that the update is at the bottom of the while block, meaning that if I want to have a continue embedded somewhere in it I have to: use duplicate code for the complicated/awkard update, AND run the risk of forgetting it and having my code infinite loop I could go the route of hand-rolling a complicated iterator: def complicated_iterator(val): while <awkward/complicated test case>: yeild val val = <awkward/complicated update> for val in complicated_iterator(start_val): if <random check>: continue # no issues here # do stuff This strikes me as waaaaay too verbose and complicated. Do folks in stack overflow have a simpler suggestion?

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• What are some good books on software testing/quality?

  - by mjh2007

  I'm looking for a good book on software quality. It would be helpful if the book covered: The software development process (requirements, design, coding, testing, maintenance) Testing roles (who performs each step in the process) Testing methods (white box and black box) Testing levels (unit testing, integration testing, etc) Testing process (Agile, waterfall, spiral) Testing tools (simulators, fixtures, and reporting software) Testing of embedded systems The goal here is to find an easy to read book that summarizes the best practices for ensuring software quality in an embedded system. It seems most texts cover the testing of application software where it is simpler to generate automated test cases or run a debugger. A book that provided solutions for improving quality in a system where the tests must be performed manually and therefore minimized would be ideal.

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• Can a 32-bit RHEL4 userland work with a 64-bit kernel?

  - by James

  Is there a way to change an i386 RHEL4 machine to run an amd64 kernel, but ensure that it still builds software into same i386 binaries? On Debian this seems quite straightforward: just install an amd64 kernel (worst case, build one like this guy: http://www.debian-administration.org/users/jonesy/weblog/1) and prefix everything with "linux32". Then everything that considers uname -m will be unchanged, I just need to handle the few cases that consider uname -r. What is the Red Hat equivalent? Is the only way a full 64-bit installation on another disk and then chrooting back to the 32-bit system before anyone builds anything? (Even the best examples of that seem to be Debian-based.) Background: We make a large system that runs on (a variant of) i386 RHEL4. However, some of the larger RHEL build machines now have enough RAM that they might benefit from going 64-bit (for the kernel and maybe some of the bigger build steps). Our build system doesn't support cross-compilation.

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• Method hiding with interfaces

  - by fearofawhackplanet

  interface IFoo { int MyReadOnlyVar { get; } } class Foo : IFoo { int MyReadOnlyVar { get; set; } } public IFoo GetFoo() { return new Foo { MyReadOnlyVar = 1 }; } Is the above an acceptable way of implementing a readonly/immutable object? The immutability of IFoo can be broken with a temporary cast to Foo. In general (non-critical) cases, is hiding functionality through interfaces a common pattern? Or is it considered lazy coding? Or even an anti-pattern?

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• .NET Reflector and getters/setters issue

  - by Humberto

  I'm using an up-to-date .NET Reflector to disassemble an internal legacy app whose source code is almost impossible to recover. I need to find the cause of a nasty bug, and then possibly patch it. Reflector did a good job as usual in the re-creation of the project's structure, but soon I discovered that every property call was left "expanded" to its get_() and set_() method signatures, rendering the source code impossible to compile. A quick Visual Studio "Search/Replace" with regex solved these cases, but it's awkward. Is there a way to make Reflector behave correctly?

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• The Definition of Regular Languages

  - by AraK

  Good Day, I have tried, and burned my brain to understand the definition of Regular Languages in Discrete Mathematics and its Applications(Rosen) without reaching the goal of understanding why the definition is like that in this book. On page(789), I am rephrasing the definition: Type 3 grammars are defined as: w1 --> w2 Where w1 is a non-terminal, and w2 is of the form: w2 = aB w2 = a Where B is a non-terminal, and a is a terminal. A special case is when w1 is the starting symbol and w2 is lambda(the empty string): w1 = S S --> lambda Two questions I couldn't find an answer for. First, Why can't w2 be of the form Ba. Second, Why lambda is only allowed for the starting symbol only. The book states that, regular languages are equivalent to Finite State Automaton, and we can easily see that a we can build FSA for both cases. I took a look at other resources, and these restrictions don't exist in these resources. Thanks,

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• AJAX calls from multiple browser tabs at the same time:

  - by Bindi

  When an user tries to send AJAX requests simultaneously from multiple browser tabs, the earlier requests get completed and the page loads but the other AJAX calls are preempted. AS a result of which the response is empty for the other calls. Only one call survives. In my application using struts 2.0, JSP and javascript and the prototype framework, i found that the server response is empty in the cases mentioned above though the data gets updated in teh database with the request parameters. The onSucess event handler for Ajax.request gets called but the the response is empty. Can you please help? Thanks

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• jquery tabIndex fix

  - by Victor

  On my pages(ASP.NET 3.5) where all input controls have tab order set whenever next input control is not enabled or hidden it goes to the address bar and then to next available control. To fix this behavior, i.e. make it land to the next available control w/o going to address bar I am trying to use jQuery: $(':text,textarea,select').blur(function() { $(this).next(':text, textarea, select').filter(':enabled:visible').focus(); }); But it still goes to the adress bar in some cases. What do I need to correct here?

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• How to get extension methods on Roslyn?

  - by eestein

  I need to list all extension methods found on the file. This is what I'm doing so far (looks like it's working): var methods = nodes.OfType<MethodDeclarationSyntax>(); var extensionMethods = methods.Where(m => m.Modifiers.Any(t => t.Kind == SyntaxKind.StaticKeyword) && m.ParameterList.Parameters.Any(p => p.Modifiers.Any(pm => pm.Kind == SyntaxKind.ThisKeyword))); Even though I couldn't test all cases it looks like this is working. But I was wondering if there was a more concise way to approach this solution. Is there some sort of IsExtension or some SyntaxKind.ExtensionMethod? I took a look but could not find anything obvious, at least. I'm using the latest Roslyn Sept/12

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• SocketAsyncEventArgs and buffering while messages are in parts

  - by Rob

  C# socket server, which has roughly 200 - 500 active connections, each one constantly sending messages to our server. About 70% of the time the messages are handled fine (in the correct order etc), however in the other 30% of cases we have jumbled up messages and things get screwed up. We should note that some clients send data in unicode and others in ASCII, so that's handled as well. Messages sent to the server are a variable length string which end in a char3, it's the char3 that we break on, other than that we keep receiving data. Could anyone shed any light on our ProcessReceive code and see what could possibly be causing us issues and how we can solve this small issue (here's hoping it's a small issue!) Code below:

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• What should be done first: Code reviews or Unit tests?

  - by goldenmean

  Hello, If a developer implements code for some module and wants to get it reviewed. What should be the order : *First unit test the module after designing test cases for the module, debugging and fixing the bugs and then give the modified code for peer code review (Pros- Code to be reviewed is 'clean' to a good extent. Reduces some avoidable review comments and rework. Cons- Developer might spend large time debugging/fixing a bug which could have pointed/anticipated in peer code reviews) Or *First do the code review with peers and then go for unit testing. What are your thoughts/experience on this? I believe this approach for unit testing, code reviewing should be programming language agnostic, but it would be interesting to know otherwise(if applicable) with specific examples. -AD

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• Loop over a file and write the next line if a condition is met

  - by 111078384259264152964

  Having a hard time fixing this or finding any good hints about it. I'm trying to loop over one file, modify each line slightly, and then loop over a different file. If the line in the second file starts with the line from the first then the following line in the second file should be written to a third file. !/usr/bin/env python with open('ids.txt', 'rU') as f: with open('seqres.txt', 'rU') as g: for id in f: id=id.lower()[0:4]+'_'+id[4] with open(id + '.fasta', 'w') as h: for line in g: if line.startswith(''+ id): h.write(g.next()) All the correct files appear, but they are empty. Yes, I am sure the if has true cases. :-) "seqres.txt" has lines with an ID number in a certain format, each followed by a line with data. The "ids.txt" has lines with the ID numbers of interest in a different format. I want each line of data with an interesting ID number in its own file. Thanks a million to anyone with a little advice!

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• mmap() for large file I/O?

  - by Boatzart

  I'm creating a utility in C++ to be run on Linux which can convert videos to a proprietary format. The video frames are very large (up to 16 megapixels), and we need to be able to seek directly to exact frame numbers, so our file format uses libz to compress each frame individually, and append the compressed data onto a file. Once all frames are finished being written, a journal which includes meta data for each frame (including their file offsets and sizes) is written to the end of the file. I'm currently using ifstream and ofstream to do the file i/o, but I am looking to optimize as much as possible. I've heard that mmap() can increase performance in a lot of cases, and I'm wondering if mine is one of them. Our files will be in the tens to hundreds of gigabytes, and although writing will always be done sequentially, random access reads should be done in constant time. Any thoughts as to whether I should investigate this further, and if so does anyone have any tips for things to look out for? Thanks!

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• Content-Length header not returned from Pylons response

  - by Evgeny

  I'm still struggling to Stream a file to the HTTP response in Pylons. In addition to the original problem, I'm finding that I cannot return the Content-Length header, so that for large files the client cannot estimate how long the download will take. I've tried response.content_length = 12345 and I've tried response.headers['Content-Length'] = 12345 In both cases the HTTP response (viewed in Fiddler) simply does not contain the Content-Length header. How do I get Pylons to return this header? (Oh, and if you have any ideas on making it stream the file please reply to the original question - I'm all out of ideas there.)

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• stop background of iphone webapp from responding to swipes

  - by JoeS

  I'm making a mobile version of my website, and trying to make it feel as native as possible on the iphone. However, any background areas of the page respond to swiping gestures such that you can shift the page partway off the screen. Specifically, if the user touches and swipes left, for example, the content shifts off the edge of the screen and one can see a gray background 'behind' the page. How can this be prevented? I'd like to have the page itself be 320x480 with scroll-swiping disabled (except on list elements that I choose). I have added the following meta tags to the top of the page: <meta name="viewport" content="width=320; height=480; initial-scale=1.0; maximum-scale=1.0; user-scalable=0;"/> <meta name="apple-mobile-web-app-capable" content="yes" /> <meta name="apple-mobile-web-app-status-bar-style" content="black" /> I've also tried the following as the event handler for the touchstart, touchmove, and touchend events of the body element: function cancelTouchEvent(e) { if (!e) var e = window.event; e.cancelBubble = true; if (e.stopPropagation) e.stopPropagation(); if (e.preventDefault) e.preventDefault(); return false; } It doesn't stop the swiping behavior, but does prevent clicks on all links on the page... Any help is much appreciated. Thanks!

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• Basic question about request queues in IIS / ASP.Net

  - by larryq

  I have an ASP.Net application running under IIS 6. A simple page has two radio buttons and a submit button. If I select radio button "A" and submit the page, a lengthy PDF file is generated, which takes about a minute to build. If I select radio button "B", a small PDF is generated. (In both cases the PDF is written out to the Response object and it opens in my browser.) If I select radio button "A" and submit, then hit the red X in my browser to stop the current request, then select radio button "B" and resubmit, the page still takes a long time to process my request. No doubt my first request is still being processed on the server, but I was wondering how IIS and/or ASP.Net are queuing my requests so that fair server use is guaranteed among all users. Am I roughly correct in assuming something like this happens, and if so, how is it done?

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• javac - differences between classpath and sourcepath options

  - by Alex

  Hi, I read the Sun documentation and a lot of Q/A on SO but I'm still a little bit confuse regarding the differences between the javac options -cp and -sourcepath. Let say I have this directory structure: c:\Java\project1\src (where the .java source files are) c:\Java\project1\bin (where the .class will be or are already) The class source MainClass.java is in a package "com.mypackage" and the directory structure is ok in src. I'm in the project1 directory. I run c:\Java\Project1\javac -d bin -sourcepath src src/com/mypackage/MainClass.java or c:\Java\Project1\javac -d bin -classpath src src/com/mypackage/MainClass.java and I obtain the same result. In verbose mode, the search path for source files is src in both cases. If anybody could help me figure out the specifics of these options, it would be great. Thank you.

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• Condition checking vs. Exception handling

  - by Aidas Bendoraitis

  When is exception handling more preferable than condition checking? There are many situations where I can choose using one or the other. For example, this is a summing function which uses a custom exception: # module mylibrary class WrongSummand(Exception): pass def sum_(a, b): """ returns the sum of two summands of the same type """ if type(a) != type(b): raise WrongSummand("given arguments are not of the same type") return a + b # module application using mylibrary from mylibrary import sum_, WrongSummand try: print sum_("A", 5) except WrongSummand: print "wrong arguments" And this is the same function, which avoids using exceptions # module mylibrary def sum_(a, b): """ returns the sum of two summands if they are both of the same type """ if type(a) == type(b): return a + b # module application using mylibrary from mylibrary import sum_ c = sum_("A", 5) if c is not None: print c else: print "wrong arguments" I think that using conditions is always more readable and manageable. Or am I wrong? What are the proper cases for defining APIs which raise exceptions and why?

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• Fastest method for SQL Server inserts, updates, selects

  - by Ian

  I use SPs and this isn't an SP vs code-behind "Build your SQL command" question. I'm looking for a high-throughput method for a backend app that handles many small transactions. I use SQLDataReader for most of the returns since forward only works in most cases for me. I've seen it done many ways, and used most of them myself. Methods that define and accept the stored procedure parameters as parameters themselves and build using cmd.Parameters.Add (with or without specifying the DB value type and/or length) Assembling your SP params and their values into an array or hashtable, then passing to a more abstract method that parses the collection and then runs cmd.Parameters.Add Classes that represent tables, initializing the class upon need, setting the public properties that represent the table fields, and calling methods like Save, Load, etc I'm sure there are others I've seen but can't think of at the moment as well. I'm open to all suggestions.

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• How to get parent node in Stanford's JavaNLP?

  - by roddik

  Hello. Suppose I have such chunk of a sentence: (NP (NP (DT A) (JJ single) (NN page)) (PP (IN in) (NP (DT a) (NN wiki) (NN website)))) At a certain moment of time I have a reference to (JJ single) and I want to get the NP node binding A single page. If I get it right, that NP is the parent of the node, A and page are its siblings and it has no children (?). When I try to use the .parent() method of a tree, I always get null. The API says that's because the implementation doesn't know how to determine the parent node. Another method of interest is .ancestor(int height, Tree root), but I don't know how to get the root of the node. In both cases, since the parser knows how to indent and group trees, it must know the "parent" tree, right? How can I get it? Thanks

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• Surrogate key for date dimension?

  - by Navin

  There are 2 school of thoughts : Use surrogate key preferbly in the format of YYYYMMDD as this will always be sequential. Eliminate Date dimension surrogate key and use actual date instead. My Questions to experts on dimension modeling are : 1> Which design would you prefer and why ? 2> How should we handle unknown values in each of the cases, Can we simply place NULL in Fact table for unknown dates as Foreign Key can be NULL (if no why)? 3> If we need to partition fact table on date column ,how would we achieve that in case 1. I am inclined towards using actual date and using NULL to represent UNKNOWN dates in fact table , as date related validation on fact can be done without need to look in to dimension table.

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• Binary Search Tree node removal

  - by doc

  I've been trying to implement a delete function for a Binary Search Tree but haven't been able to get it to work in all cases. This is my latest attempt: if(t->get_left() == empty) *t = *t->get_left(); else if(t->get_right() == empty) *t = *t->get_right(); else if((t->get_left() != empty) && (t->get_right() != empty)) { Node* node = new Node(t->get_data(), t->get_parent(), t->get_colour(), t->get_left(), t->get_right()); *t = *node; } t is a node and empty is just a node with nothing in it. I'm just trying to swap the values but I'm getting a runtime error. Any ideas? Thanks

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• Using a "vo" for joined data?

  - by keithjgrant

  I'm building a small financial system. Because of double-entry accounting, transactions always come in batches of two or more, so I've got a batch table and a transaction table. (The transaction table has batch_id, account_id, and amount fields, and shared data like date and description are relegated to the batch table). I've been using basic vo-type models for each table so far. Because of this table structure structure, though, transactions will almost always be selected with a join on the batch table. So should I take the selected records and splice them into two separate vo objects, or should I create a "shared" vo that contains both batch and transaction data? There are a few cases in which batch records and/or transaction records. Are there possible pitfalls down the road if I have "overlapping" vo classes?

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• Access violation exception from Delphi's Supports -> QueryInterface

  - by Sharon

  Hi, I have the following piece of code: for i := 0 to FControlList.Count - 1 do if Supports(IMyControl(FControlList[i]), IMyControlEx) then begin MyControlEx := IMyControl(FControlList[i]) as IMyControlEx; MyControlEx.DoYourMagic(Self, SomeData); end; This code is called many times during my application execution, but in some specific cases it fails inside the Supports() method. And more specifically - it seems to fall inside the QueryInterface() call within the Supports() method. I checked that FControlList is not nil and FControlList[i] is not nil and it still happens. Any idea will be appreciated!!!

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