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  • Real life example fo Floating Point error

    - by Rob
    Is there any examples of a company that was burned by floating point data that caused a rounding issue? We're implementing a new system and all the monetary values are stored in floats. I think if i can show actual examples of why this has failed it'll have more weight than the theory of why the values can't be stored properly.

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  • How do I pass an ArrayList to method that takes a collection as an input

    - by Ankur
    I want to pass some ArrayList X into method a(Collection someCol) that takes Collection as an input. How can I do this? I thought an ArrayList was a Collection and thus I should be able to "just do it" but it seems that Collection is an interface and ArrayList implements this interface. Is there something I can do to make this work ... if you understand the theory that would also help me and possibly lots of other people. Thanks

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  • How can I represent a line of music notes in a way that allows fast insertion at any index?

    - by chairbender
    For "fun", and to learn functional programming, I'm developing a program in Clojure that does algorithmic composition using ideas from this theory of music called "Westergaardian Theory". It generates lines of music (where a line is just a single staff consisting of a sequence of notes, each with pitches and durations). It basically works like this: Start with a line consisting of three notes (the specifics of how these are chosen are not important). Randomly perform one of several "operations" on this line. The operation picks randomly from all pairs of adjacent notes that meet a certain criteria (for each pair, the criteria only depends on the pair and is independent of the other notes in the line). It inserts 1 or several notes (depending on the operation) between the chosen pair. Each operation has its own unique criteria. Continue randomly performing these operations on the line until the line is the desired length. The issue I've run into is that my implementation of this is quite slow, and I suspect it could be made faster. I'm new to Clojure and functional programming in general (though I'm experienced with OO), so I'm hoping someone with more experience can point out if I'm not thinking in a functional paradigm or missing out on some FP technique. My current implementation is that each line is a vector containing maps. Each map has a :note and a :dur. :note's value is a keyword representing a musical note like :A4 or :C#3. :dur's value is a fraction, representing the duration of the note (1 is a whole note, 1/4 is a quarter note, etc...). So, for example, a line representing the C major scale starting on C3 would look like this: [ {:note :C3 :dur 1} {:note :D3 :dur 1} {:note :E3 :dur 1} {:note :F3 :dur 1} {:note :G3 :dur 1} {:note :A4 :dur 1} {:note :B4 :dur 1} ] This is a problematic representation because there's not really a quick way to insert into an arbitrary index of a vector. But insertion is the most frequently performed operation on these lines. My current terrible function for inserting notes into a line basically splits the vector using subvec at the point of insertion, uses conj to join the first part + notes + last part, then uses flatten and vec to make them all be in a one-dimensional vector. For example if I want to insert C3 and D3 into the the C major scale at index 3 (where the F3 is), it would do this (I'll use the note name in place of the :note and :dur maps): (conj [C3 D3 E3] [C3 D3] [F3 G3 A4 B4]), which creates [C3 D3 E3 [C3 D3] [F3 G3 A4 B4]] (vec (flatten previous-vector)) which gives [C3 D3 E3 C3 D3 F3 G3 A4 B4] The run time of that is O(n), AFAIK. I'm looking for a way to make this insertion faster. I've searched for information on Clojure data structures that have fast insertion but haven't found anything that would work. I found "finger trees" but they only allow fast insertion at the start or end of the list. Edit: I split this into two questions. The other part is here.

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  • is there a proper way to handle multiple errors/exceptions?

    - by toPeerOrNotToPeer
    in OO programming, is there some conceptual pattern, ideas, about handling multiple errors? for example, i have a method that performs some checks and should return an error message for each error found ['name is too short', 'name contains invalid unicode sequences', 'name is too long'] now, should i use an array of exceptions (not thrown exceptions)? or something like this is better: class MyExceptionList extends Exception{ public Void addException(Exception e){} public Array getExceptions(){} } any theory behind this argument will be appreciated! (this isn't a request about a specific programming language, but a pure theoretical one) thank you in advance

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  • Python multithreading, How is it using multiple Cores?

    - by Sabirul Mostofa
    I am running a multithreaded application(Python2.7.3) in a Intel(R) Core(TM)2 Duo CPU E7500 @ 2.93GHz. I thought it would be using only one core but using the "top" command I see that the python processes are constantly changing the core no. Enabling "SHOW THREADS" in the top command shows diffrent thread processes working on different cores. Can anyone please explain this? It is bothering me as I know from theory that multithreading is executed on a single core.

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  • PHP debugging or performance Hook

    - by Joshua
    In an interpreted language like PHP it is possible in theory to set up some sort of callback function that would be run indiscriminately after every line of code. I am wondering if such a thing exists in PHP or if such a thing could be accomplished in any way? Such a feature could be useful for diagnostics or performance tests. Does anyone know of such a mechanism in PHP?

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  • Is there possible in clojure to make a deadlock (or anything bad case) using agents?

    - by hsestupin
    CLojure agents is powerful tool. So actions to the agents are asynchronously sent using functions "send" and "send-off". And in theory there couldn't appear something like deadlock. Is there possible to write some clojure code (for example invoking from some action another action to another agent) using agents in which we have some concurrency problem - it could be deadlock, race condition or anything else. (guys, i'm very sorry for my english)

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  • What are the latest tools that I can use to write a DSL (Domain-specific language) in 2009 Sep?

    - by servicesxiaodai
    I looked into Logix and EasyExtend for Python. Logix hasn't been around for a while and it failed to install on Python 2.6. EasyExtend's tutorial is hopeless, the code in the tutorial doesn't even work. I am looking for something so I can write my DSL. My DSL will be used as a research tool. And I don't want to spend time learning all that parsing and compiler theory.

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  • Functional Programming Equivalent of Design Patterns Book?

    - by JasonFruit
    Is there a functional-programming equivalent to the Gang of Four Design Patterns book? That is, is there a book that explains and gives examples of how commonly-needed code structures are implemented functionally? I think seeing that would give me a better idea of how to go about using in practice the functional concepts whose theory I understand.

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  • Scaling vectors from a center point?

    - by user146780
    I'm trying to figure out if I have points that make for example a square: * * * * and let's say I know the center of this square. I want a formula that will make it for eample twice its size but from the center * * * * * * * * Therefore the new shape is twice as large and from the center of the polygon. It has to work for any shape not just squares. I'm looking more for the theory behind it more than the implementation. Thanks

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  • Exception in the OnIdle event does not bubble up

    - by sthay
    On my main form, I subscribed to two events: Application.ThreadException and Application.Idle. In theory, any exception that is not caught should get bubbled up to the main form. However, this does not work if the exception happens in the OnIdle event. The system just crashes. Does anyone know how to solve this problem? Thanks so much.

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  • .NET Compact Framework app that will run on both Professional and Standard

    - by CJCraft.com
    Is there any guidance on creating apps that will run on both professional (touch-screen) and standard (non-touch-screen) devices. I have a simple application that is mostly text and buttons that in theory should be able to run on both professional and standard devices with little if any modification. It seems the IDE wants to make this hard to impossible, but I expect it to be possible. Any advice?

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  • Localization of icon and default screen in iPhone

    - by hgpc
    Can the app icon and default screen be localized in iPhone? Has anyone tried it? In theory it should be possible as they're just image resources, but I found no explicit mention of this in the documentation, and I wouldn't like to have my app rejected or failing for this.

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  • ODBC in SSIS 2012

    - by jamiet
    In August 2011 the SQL Server client team published a blog post entitled Microsoft is Aligning with ODBC for Native Relational Data Access in which they basically said "OLE DB is the past, ODBC is the future. Deal with it.". From that blog post:We encourage you to adopt ODBC in the development of your new and future versions of your application. You don’t need to change your existing applications using OLE DB, as they will continue to be supported on Denali throughout its lifecycle. While this gives you a large window of opportunity for changing your applications before the deprecation goes into effect, you may want to consider migrating those applications to ODBC as a part of your future roadmap.I recently undertook a project using SSIS2012 and heeded that advice by opting to use ODBC Connection Managers rather than OLE DB Connection Managers. Unfortunately my finding was that the ODBC Connection Manager is not yet ready for primetime use in SSIS 2012. The main issue I found was that you can't populate an Object variable with a recordset when using an Execute SQL Task connecting to an ODBC data source; any attempt to do so will result in an error:"Disconnected recordsets are not available from ODBC connections." I have filed a bug on Connect at ODBC Connection Manager does not have same funcitonality as OLE DB. For this reason I strongly recommend that you don't make the move to ODBC Connection Managers in SSIS just yet - best to wait for the next version of SSIS before doing that.I found another couple of issues with the ODBC Connection Manager that are worth keeping in mind:It doesn't recognise System Data Source Names (DSNs), only User DSNs (bug filed at ODBC System DSNs are not available in the ODBC Connection Manager)  UPDATE: According to a comment on that Connect item this may only be a problem on 64bit.In the OLE DB Connection Manager parameter ordinals are 0-based, in the ODBC Connection Manager they are 1-based (oh I just can't wait for the upgrade mess that ensues from this one!!!)You have been warned!@jamiet

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  • LLBLGen Pro v3.0 with Entity Framework v4.0 (12m video)

    - by FransBouma
    Today I recorded a video in which I illustrate some of the database-first functionality available in LLBLGen Pro v3.0. LLBLGen Pro v3.0 also supports model-first functionality, which I hope to illustrate in an upcoming video. LLBLGen Pro v3.0 is currently in beta and is scheduled to RTM some time in May 2010. It supports the following frameworks out of the box, with more scheduled to follow in the coming year: LLBLGen Pro RTL (our own o/r mapper framework), Linq to Sql, NHibernate and Entity Framework (v1 and v4). The video I linked to below illustrates the creation of an entity model for Entity Framework v4, by reverse engineering the SQL Server 2008 example database 'AdventureWorks'. The following topics (among others) are included in the video: Abbreviation support (example: convert 'Qty' into 'Quantity' during name construction) Flexible, framework specific settings Attribute definitions for various elements (so no requirement for buddy-classes or messing with generated code or templates) Retrieval of relational model data from a database Reverse engineering of tables into entities, automatically placed in groups Auto-creation of inheritance hierarchies Refactoring of entity fields into Value Type Definitions (DDD) Mapping a Typed view onto a stored procedure resultset Creation of a Typed list (definition of a query with a projection) on a set of related entities Validation and correction of found inconsistencies and errors Generating code using one of the pre-defined presets Illustration of the code in vs.net 2010 It also gives a good overview of what it takes with LLBLGen Pro v3.0 to start from a new project, point it to a database, get an entity model, perform tweaks and validation and generate code which is ready to run. I am no video recording expert so there's no audio and some mouse movements might be a little too quickly. If that's the case, please pause the video. It's rather big (52MB). Click here to open the HTML page with the video (Flash). Opens in a new window. LLBLGen Pro v3.0 is currently in beta (available for v2.x customers) and scheduled to be released somewhere in May 2010.

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  • AWS RDS (SQL Server): SSL Connection - The target principal name is incorrect

    - by AX1
    I have a Amazon Web Services (AWS) Relational Database Service (RDS) instance running SQL Server 2012 Express. I've installed Amazon's aws.amazon.com/rds certificate in the client machine's Trusted Root Certification Authorities store. However, when I connect to the RDS instance (using SQL Server Management Studio 2012) and check off "Encrypt Connection", I get the following error: A connection was successfully established with the server, but then an error occurred during the login process. (provider: SSL Provider, error: 0 - The target principal name is incorrect.) (Microsoft SQL Server) What does this mean, and how can I fix it? Thanks!

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  • SQLAuthority News – Microsoft SQL Server 2008 R2 – PowerPivot for Microsoft Excel 2010

    - by pinaldave
    Microsoft has really and truly created some buzz for PowerPivot. I have been asked to show the demo of Powerpivot in recent time even when I am doing relational database training. Attached is the few details where everyone can download PowerPivot and use the same. Microsoft SQL Server 2008 R2 – PowerPivot for Microsoft Excel 2010 – RTM Microsoft® PowerPivot for Microsoft® Excel 2010 provides ground-breaking technology, such as fast manipulation of large data sets (often millions of rows), streamlined integration of data, and the ability to effortlessly share your analysis through Microsoft® SharePoint 2010. Microsoft PowerPivot for Excel 2010 Samples Microsoft® PowerPivot for Microsoft® Excel 2010 provides ground-breaking technology, such as fast manipulation of large data sets (often millions of rows), streamlined integration of data, and the ability to effortlessly share your analysis through Microsoft® SharePoint 2010. Download examples of the types of reports you can create. Microsoft PowerPivot for Excel 2010 Data Analysis Expressions Sample version 1.0 Microsoft® PowerPivot for Microsoft® Excel 2010 provides ground-breaking technology, such as fast manipulation of large data sets (often millions of rows), streamlined integration of data, and the ability to effortlessly share your analysis through Microsoft® SharePoint 2010. Download this PowerPivot workbook to learn more about DAX calculations. Note: The brief description below the download link is taken from respective download page. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: SQL, SQL Authority, SQL Documentation, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Book Review: &ldquo;Inside Microsoft SQL Server 2008: T-SQL Querying&rdquo; by Itzik Ben-Gan et al

    - by Sam Abraham
    In the past few weeks, I have been reading “Inside Microsoft SQL Server 2008: T-SQL Querying” by Itzik Ben-Gan et al. In the next few lines, I will be providing a quick book review having finished reading this valuable resource on SQL Server 2008. In this book, the authors have targeted most of the common as well as advanced T-SQL Querying scenarios that one would use for development on a SQL Server database. Book content covered sufficient theory and practice to empower its readers to systematically write better performance-tuned queries. Chapter one introduced a quick refresher of the basics of query processing. Chapters 2 and 3 followed with a thorough coverage of applicable relational algebra concepts which set a good stage for chapter 4 to dive deep into query tuning. Chapter 4 has been my favorite chapter of the book as it provided nice illustrations of the internals of indexes, waits, statistics and query plans. I particularly appreciated the thorough explanation of execution plans which helped clarify some areas I may have not paid particular attention to in the past. The book continues to focus on SQL operators tackling a few in each chapter and covering their internal workings and the best practices to follow when used. Figures and illustrations have been particularly helpful in grasping advanced concepts covered therein. In conclusion, Inside Microsoft SQL Server 2008: T-SQL Querying provided me with 750+ pages of focused, advanced and practical knowledge that has added a few tips and tricks to my arsenal of query tuning strategies. Many thanks to the O’Reilly User Group Program and its support of our West Palm Beach Developers’ Group. --Sam Abraham

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  • Create my own database system

    - by Xananax
    Ok so before I get bashed: I know it's something huge for one person; I don't care if the end product can actually be used or not. I need to learn how databases work in order to use them more efficiently, and my way of learning is by doing. So I want to create my own database system. I am not referring to creating a pseudo-database that would use query to parse files; this would simply be a filesystem interface with a query language. I am talking about the actual structure of a database engine. And since what I have in mind is neither relational nor document-oriented (it's "node-oriented", if that even exists), I would need any resource to be as abstract and high-level as possible. So how would I go about creating that? What resources/tutorials/books can I read to understand? The language does not matter in the slightest. Ideally, the code would be pseudo-code to illustrate the concept, not tied to a particular language, but anything would do. I was not able to find anything on the matter on google (since I am so illiterate on the subject, maybe I am just not entering the right search). If such resources are not available, then I guess something about how to create a client would at least be a step in the right direction.

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