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  • Precompile Lambda Expression Tree conversions as constants?

    - by Nathan
    It is fairly common to take an Expression tree, and convert it to some other form, such as a string representation (for example this question and this question, and I suspect Linq2Sql does something similar). In many cases, perhaps even most cases, the Expression tree conversion will always be the same, i.e. if I have a function public string GenerateSomeSql(Expression<Func<TResult, TProperty>> expression) then any call with the same argument will always return the same result for example: GenerateSomeSql(x => x.Age) //suppose this will always return "select Age from Person" GenerateSomeSql(x => x.Ssn) //suppose this will always return "select Ssn from Person" So, in essence, the function call with a particular argument is really just a constant, except time is wasted at runtime re-computing it continuously. Assuming, for the sake of argument, that the conversion was sufficiently complex to cause a noticeable performance hit, is there any way to pre-compile the function call into an actual constant?

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  • DataAdapter Select string from base table schema?

    - by MattSlay
    When I built my .xsd, I had to choose the columns for each table, and it made a schema for the tables, right? So how can I get that Select string to use as a base Select command for new instances of dataadapters, and then just append a Where and OrderBy clause to it as needed? That would keep me from having to keep each DataAdapter's field list (for the same table) in synch with the schema of that table in the .xsd file. Isn't it common to have several DataAdapters that work on a certain table schema, but with different params in the Where and OrderBy clauses? Surely one does not have to maintain (or even redundently build) the field list part of the Select strings for half a dozen DataAdapters that all work off of the same table schema. I'm envisioning something like this pseudo code: BaseSelectString = MyTypedDataSet.JobsTable.GetSelectStringFromSchema() // Is there such a method or technique? WhereClause = " Where SomeField = @Param1 and SomeOtherField = @Param2" OrderByClause = " Order By Field1, Field2" SelectString=BaseSelectString + WhereClause + OrderByClause OleDbDataAdapter adapter = new OleDbDataAdapter(SelectString, MyConn)

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  • Why are my hard drives failing?

    - by WishCow
    I have a small Ubuntu server running at home, with 2 HDDs. There are two software raids (raid1) on the disks, managed by mdadm, which I believe is irrelevant, but mentioning it anyway. Both of the HDDs are Western Digital, and have been used for around 2 years, when one of them started making clicking noises, and died. I figured that maybe it's natural after 2 years, so I bought a new one, and resynced the raid arrays. After about a month, the other drive also died. I didn't get suspicious, since both drives have been bought at the same time, it's not that surprising to see both of them near each other, so I bought another one. So far, 2 old drives failed, and 2 brand new in the system. After one month, one of the new drives died. This is when it started getting suspicious. Since the PC was put together from some really old parts (think AthlonXP), I figured that maybe the motherboard's SATA controller is the culprit. Of course you can't switch parts easily in an old PC like this, so I bought a whole system, new MB, new CPU, new RAM. Took the just failed drive back, since it was under warranty, and got it replaced. So it is up to 2 failed drives from the old ones, and 1 failed drive from the new ones. No problems, for 1 month. After that errors were creeping up again in /var/log/messages, and mdadm was reporting raid array failures. I started tearing my hair out. Everything is new in the system, it's up to the third brand new HDD, it's simply not possible that all of the new drives that I bought were faulty. Let's see what is still common... the cables. Okay, long shot, let's replace the SATA cables. Take HDD back, smile to the guy at the counter and say that I'm really unlucky. He replaces the HDD. I come home, one month passes and one of HDDs fails, again. I'm not joking. Two of the brand new HDDs have failed. Maybe it's a bug in the OS. Let's see what the manufacturer's testing tool says. Download testing tool, burn it to a CD, reboot, leave HDD testing overnight. Test says that the drive is faulty, and I should back up everything, if I still can. I don't know what's happening, but it does not look like a software problem, something is definitely thrashing the HDDs. I should mention now, that the whole system is in a shoebox. Since there are a load of "build your own ikea case" stuff, I thought there shouldn't be any problems throwing the thing in a box, and stuffing it away somewhere. The box is well ventilated, but I thought that just maybe the drives were overheating. There is no other possible answer to this. So I took the HDD back, and got it replaced (for the 3rd time), and bought HDD coolers. And just now, I have heard the sound of doom. click click whizzzzzzzzz. SSH into the box: You have new mail! mail r 1 DegradedArrayEvent on /dev/md0 ... dmesg output: [47128.000051] ata3: lost interrupt (Status 0x50) [47128.000097] end_request: I/O error, dev sda, sector 58588863 [47128.000134] md: super_written gets error=-5, uptodate=0 [48043.976054] ata3: lost interrupt (Status 0x50) [48043.976086] ata3.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [48043.976132] ata3.00: cmd c8/00:18:bf:40:52/00:00:00:00:00/e1 tag 0 dma 12288 in [48043.976135] res 40/00:00:00:4f:c2/00:00:00:00:00/00 Emask 0x4 (timeout) [48043.976208] ata3.00: status: { DRDY } [48043.976241] ata3: soft resetting link [48044.148446] ata3.00: configured for UDMA/133 [48044.148457] ata3.00: device reported invalid CHS sector 0 [48044.148477] ata3: EH complete Recap: No possibility of overheating 6 drives have failed, 4 of those have been brand new. I'm not sure now that the original two have been faulty, or suffered the same thing that the new ones. There is nothing common in the system, apart from the OS which is Ubuntu Karmic now (started with Jaunty). New MB, new CPU, new RAM, new SATA cables. No, the little holes on the HDD are not covered I'm crying. Really. I don't have the face to return to the store now, it's not possible for 4 drives to fail under 4 months. A few ideas that I have been thinking: Is it possible that I fuck up something when I partition and resync the drives? Can it be so bad that it physicaly wrecks the drive? (since the vendor supplied tool says that the drive is damaged) I do the partitoning with fdisk, and use the same block size for the raid1 partitions (I check the exact block sizes with fdisk -lu) Is it possible that the linux kernel or mdadm, or something is not compatible with this exact brand of HDDs, and thrashes them? Is it possible that it may be the shoebox? Try placing it somewhere else? It's under a shelf now, so humidity is not a problem either. Is it possible that a normal PC case will solve my problem (I'm going to shoot myself then)? I will get a picture tomorrow. Am I just simply cursed? Any help or speculation is greatly appreciated. Edit: The power strip is guarded against overvoltage. Edit2: I have moved inbetween these 4 months, so the possibility of the cause being "dirty" electricity in both places, is very low. Edit3: I have checked the voltages in the BIOS (couldn't borrow a multimeter), and they are all seem correct, the biggest discrepancy is in the 12V, because it's supplying 11.3. Should I be worried about that? Edit4: I put my desktop PC's PSU into the server. The BIOS reported much more accurate voltage readings, and also it has successfully rebuilt the raid1 array, which took some 3-4 hours, so I feel a little positive now. Will get a new PSU tomorrow to test with that. Also, attaching the picture about the box: (disregard the 3rd drive)

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  • asp.net free cms for library

    - by Andrew Florko
    We have library website written in classic ASP that allows to browse and search by multiple (50+) filter criterias (author, publication year, ISSN ... ). There are lots of security holes and we have only one developer who hardly maintain this ASP-site with some minor features for last 3 years. There are two common user groups - administrators (librarians) and students (5000+) who have books on hands and searches for them. We don't want to rewrite it from scratch, just to use standard free CMS (.net based) and migrate library data and user accounts with minimum effort. What CMS will you suggest? Thank you in advance.

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  • Stop browser from filling textboxes with details

    - by TenaciousImpy
    Hi, I've run into a really annoying problem, and I'm hoping it's just a setting I've missed. I've got an ASP.NET application which allows users to enter their username/password in various places (e.g. login, change password, change username etc..). When I logged in, the browser asked if I would like to store the user details. Usually, I click 'no', but this time I decided to click 'yes'. Now, certain textboxes in my form are prefilled with the username or password. Is it possible to remove these, as they sometimes appear in textboxes which shouldn't be prefilled. I tried setting AutoCompleteType=none and Text='' but it still gets prefilled. The textboxes don't have much in common, except the same CssClass and, for password boxes, TextMode=password. The names are different, although sometimes they include the word name (e.g. fullName, userName). Is there a way to stop the browser from filling certain textboxes? Thanks

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  • Matlab tutorial for programmers

    - by Jonas
    I'm getting some new students soon, who will be writing Matlab code. They're new to Matlab, but they have experience coding in Java and C++. I'm going to have them go through the 'Getting Started' section of the Matlab help. In addition, I want to give a small tutorial with the goal to prevent them from making some of the most common mistakes people make when switching to Matlab ("Matlab starts counting at 1"), and show them some features that they may not be aware of when coming from other languages ("you can subtract a scalar directly from an array, and for vectors, there's bsxfun"). What are the most important things I should tell them?

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  • Illustration for code presentation

    - by Lasse V. Karlsen
    I got an odd request, and I fear it will be closed as off-topic. So be it, but it's worth a shot. I'm creating a presentation about dependency injection and inversion of control, and I thought I'd make the point of interchangeable parts that serve a common purpose, but has different implementations, by showing an image I've seen before. Basically the image is of a man or a woman, but the image is split up into four parts: Head Torso uhm... not sure the name of this part, stomach, etc. Legs Possibly a fifth with feet and for each part you can choose among a few variants, creating odd people in the process. ie. a man torso with a woman head. But, I can't find such an image now of course. Does anyone know of such an image and can provide me with an url?

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  • translate by replacing words inside existing text

    - by Berry Tsakala
    What are common approaches for translating certain words (or expressions) inside a given text, when the text must be reconstructed (with punctuations and everythin.) ? The translation comes from a lookup table, and covers words, collocations, and emoticons like L33t, CUL8R, :-), etc. Simple string search-and-replace is not enough since it can replace part of longer words (cat dog ? caterpillar dogerpillar). Assume the following input: s = "dogbert, started a dilbert dilbertion proces cat-bert :-)" after translation, i should receive something like: result = "anna, started a george dilbertion process cat-bert smiley" I can't simply tokenize, since i loose punctuations and word positions. Regular expressions, works for normal words, but don't catch special expressions like the smiley :-) but it does . re.sub(r'\bword\b','translation',s) ==> translation re.sub(r'\b:-\)\b','smiley',s) ==> :-) for now i'm using the above mentioned regex, and simple replace for the non-alphanumeric words, but it's far from being bulletproof. (p.s. i'm using python)

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  • Code reading: where can i read great, modern, and well-documented C++ code?

    - by baol
    Reading code is one of the best ways to learn new idioms, tricks, and techniques. Sadly it's very common to find badly written C++ code. Some use C++ as it was C, others as if it was Java, some just shoot in their feet. I believe gtkmm is a good example of C++ design, but a binding could not be the better code to read (you need to know the C library behind that). Boost libraries (at least the one I read) tend to be less readable than I'd like. Can you mention open source projects (or other projects which source is freely readable) that are good example of readable, modern, well-documented, and auto-contained, C++ code to learn from? (I believe that one project per answer will be better, and I'd include the motivation that led you to selecting that one.)

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  • What is your longest-held programming assumption that turned out to be incorrect?

    - by Demi
    I am doing some research into common errors and poor assumptions made by junior (and perhaps senior) software engineers. What was your longest-held poor assumption that was eventually corrected? For example: I at one point failed to understand that the size of an integer was not a standard (depends on the language and target). A bit embarrassing to state, but there it is. Be frank: what hard-held belief did you have, and roughly how long did you maintain the assumption? It can be about an algorithm, a language, a programming concept, testing, anything under the computer science domain.

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  • How do I debug random Timeout::Error: execution expired

    - by ChrisH
    We are using Rails 2.3.5 and have been experiencing seemingly random Timeout::Error: execution expired errors. The errors reported by Hoptoad are not consistently in any particular controller and show up everywhere from user sessions to account settings to some of our core functionality controllers. The vast majority of requests do not Timeout but there are enough to cause concern. Is this normal? If so, what are some things to look at to decrease the occurance? If not, has anyone run into this and what are some common problems that can trigger an error like this.

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  • Help repaiting a Component

    - by serhio
    I am working with Microsoft.VisualBasic.PowerPacks.RectangleShape, but the question is common for components or controls in general. I added to a TextRectangleShape : RectangleShape a Text property: Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs) MyBase.OnPaint(e) Dim f As Font = Me.Font Dim g As Graphics = e.Graphics Dim textRect As Rectangle = New Rectangle(Me.Location, Me.Size) Using br As New SolidBrush(Me._TextColor) g.DrawString(_Text, f, br, textRect) End Using End Sub Now when I move this control the text does not disappear from the former location. Maybe I could invalidate each time the Parent in the OnPaint, but if this is not a good solution if the parent has a time consuming repaint logic or I have a lot of my custom component moving at the same time. How do I properly repaint the component?

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  • CSS repeat pattern with linear gradient

    - by luca
    I'm on my first approach with photoshop patterns.I'm buildin a webpage where I want to use my pattern to give a nice effect to my webpage background. The pattern I found is 120x120 px If I was done here I should use this css: background-imag:url(mypattern.jpg); background-repeat:repeat; But Im not done.Id like to *add to my page's background a linear gradient(dir=top/down col=light-blue/green) with the pattern fill layer on top of it, with blending mode=darken *. This is the final effect: I come to the point. QUESTION: Combining linear vertical-gradient effect and my 120x120 pattern is it possible to find a pattern that I could use to repeat itself endlessly both vertical and horizontal??which is a common solution in this case? Hope It's clear thanks Luca

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  • DNS Lookup in ASP / ASP.Net

    - by Dave Forgac
    I have a Windows server that is intermittently losing the ability to lookup DNS information. I'm trying to get to the root cause of the problem but in the mean time I'd like to be able to monitor whether the server can perform lookups. Basically, it should attempt to lookup some common hostnames and the display 'Success' if the lookups are successful. I see lots of examples of doing this with third party components in ASP but I would prefer to be able to do this with a single ASP / ASP.Net script that would be portable and not require anything additional be installed.

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  • How are vector patterns used in syntax-rules?

    - by Jay
    Hi, I have been writing Common Lisp macros, so Scheme's R5Rs macros are a bit unnatural to me. I think I got the idea, except that I don't understand how one would use vector patterns in syntax-rules: (define-syntax mac (syntax-rules () ((mac #(a b c d)) (let () (display a) (newline) (display d) (newline))))) (expand '(mac #(1 2 3 4))) ;; Chicken's expand-full extension shows macroexpansion => (let746 () (display747 1) (newline748) (display747 4) (newline748)) I don't see how I'd use a macro that requires its arguments to be written as a vector: (mac #(1 2 3 4)) => 1 4 Is there some kind of technique that uses those patterns? Thank you!

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  • Can SVG render partially if gzipped and chunk-transferred?

    - by Scott Stafford
    Hi - I have some large, dynamically generated SVGs that are being served over a relatively slow internet connection. I'm trying to optimize them to be viewable as fast as possible. If I set the server to Content-Encoding: gzip and Transfer-Encoding: chunked, will any SVG viewers take advantage of that and render it partially, as it is transferred? If not, are there other ways to get it to render as-it-streams? I could break it up into several SVG pieces but that will be a lot of work, I was hoping for server settings... The most common users use IE7 with the Adobe SVG Viewer plugin. I doubt it matters but I'm serving with C#/ASP.NET and IIS6.

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  • Using different languages in one project

    - by Tarbal
    I recently heard about the use of several different languages in a (big) project, I also read about famous services such as Twitter using Rails as frontend, mixed with some other languages, and Scala I think it was as backend. Is this common practice? Who does that? I'm sure there are disadvantages to this. I think that you will have problems with the different interpreters/compilers and seamlessly connecting the different languages. Is this true? Why is this actually done? For performance?

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  • Good input validation loop using cin - C++

    - by Alex
    Hi there, I'm in my second OOP class, and my first class was taught in C#, so I'm new to C++ and currently I am practicing input validation using cin. So here's my question: Is this loop I constructed a pretty good way of validating input? Or is there a more common/accepted way of doing it? Thanks! Code: int taxableIncome; int error; // input validation loop do { error = 0; cout << "Please enter in your taxable income: "; cin >> taxableIncome; if (cin.fail()) { cout << "Please enter a valid integer" << endl; error = 1; cin.clear(); cin.ignore(80, '\n'); } }while(error == 1);

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  • Django template not loading javascript and css properly due to urlpatterns

    - by fmsf
    Hey, When this one runs everything goes fine: (r"^newobject$", "views.myobjects.newobject"), All the CSS + JS files are properly fetched from: static/css/... static/js/... When this one runs: (r"^mybjects/(([a-z]|[A-Z]|[0-9])+)$","views.myobjects.loadobject"), All the css and JS files that are being fetched, are run trough the urlpatterns and are returning my defailt page: (r"", 'views.main.index'), This makes all my CSS and JS code to actualy be HTML. My guess is that i'm giving some noob mistake. Is there any common reason why this should happen? And how to fix it?

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  • IIS7 + ASP.NET MVC Client Caching Headers Not Working

    - by Tobin Harris
    Hey folks I've deployed an ASP.NET MVC app on IIS7 and Windows Server 2008. I've read posts on here, and around the web, but can't get the darn client-side caching to work. I'm trying to cache everything in the /Content folder. So far I've select that folder in IIS manager, and set the appropriate HTTP Response Headers (under Common Headers). I've also checked the web.config file in the /Content folder and the values there are being set. All resources in /Content come back with this (from FireBug): Cache-Control no-cache, no-store, must-revalidate Pragma no-cache Content-Type image/png Expires -1 Last-Modified Sun, 11 Oct 2009 19:01:40 GMT Accept-Ranges bytes Etag "f318d643a54aca1:0" Server Microsoft-IIS/7.0 X-Powered-By ASP.NET Date Sun, 11 Oct 2009 20:40:01 GMT Content-Length 620 Note the Cache-Control and Expires values for this static image being requested. The site is currently compiled in Debug (this will change), but surely that wouldn't make a difference? Obviously I'm overlooking something, any ideas would be appreciated. Thanks

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  • Simple but efficient way to store a series of small changes to an image?

    - by finnw
    I have a series of images. Each one is typically (but not always) similar to the previous one, with 3 or 4 small rectangular regions updated. I need to record these changes using a minimum of disk space. The source images are not compressed, but I would like the deltas to be compressed. I need to be able to recreate the images exactly as input (so a lossy video codec is not appropriate.) I am thinking of something along the lines of: Composite the new image with a negative of the old image Save the composited image in any common format that can compress using RLE (probably PNG.) Recreate the second image by compositing the previous image with the delta. Although the images have an alpha channel, I can ignore it for the purposes of this function. Is there an easy-to-implement algorithm or free Java library with this capability?

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  • How to add file revision (not the last changed revision) to Subclipse "Label decorations"?

    - by mlvljr
    Firstly, please beware I'm new to SVN. Then, my question has much in common with Get current revision number in Subclipse?. The (seeming) problem is (I use Ecpilse v3.5.0 (build id I20090611-1540)): My freshly installed Subclipse plugin offers "revision - last revision loaded into workspace" label under "Windows > Preferences > Team > SVN > Label decorations" That seems to correspond to "Last changed revision" under "File > Properties > Subversion" (and not the "Revision" there). Hence, the question.

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  • PHP Dynamic Breadcrumb, small modification

    - by Adrian M.
    Hello, I got this code from someone and it works very well, I just want to remove the link from the last element of the array: //get rid of empty parts $crumbs = array_filter($crumbs); $result = array(); $path = ''; foreach($crumbs as $crumb){ $path .= '/' . $crumb; $name = ucfirst(str_replace(array(".php","_"),array(""," "), $crumb)); $result[] = "<a href=\"$path\">$name</a>"; } print implode(' > ', $result); This will output for example: Content Common File I just want a to remove the link from the last item - "File" to be just plain text.. I tried myself to count the array items and then if the array item is the last one then to print as plain text the last item.. but I'm still noob, I haven't managed to get a proper result.. Thank you!

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  • 2D World design question

    - by Maciek
    I'm facing a problem which is probably extremely common in game-design. Let's assume that we've got a 2D world The world's size is M x N rect The world may contain some items in it The items have (x,y) coords The world can be browsed via a window that is physically (m x n) large. The browser window can be zoomed in / out The browser window can be panned up/down + left right, while in the extents of the world's rect. How should I go about implementing this? I'm especially concerned about the browser window. Can anyone recommend any good reads ? This is not a homework - it's more of a task which I've set myself to complete.

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  • Map Reduce Frameworks/Infrastructure

    - by Johannes Rudolph
    Map Reduce is a pattern that seems to get a lot of traction lately and I start to see it manifest in one of my projects that is focused on an event processing pipeline (iPhone Accelerometer and GPS data). I needed to built a lot of infrastructure for this project, in fact it overweighs the logic code interacting with it by 2x. Some of the components I built where EventProcessors (with in- and output plus buffering, timing etc.), multiplexers and aggregators. This leads me to my question what the "common" required infrastrucutre for map reduce is. Since I am working with .Net a lot I can see map reduce infrastructure built into the Framework and language constructs. Functional languages support this paradigm per se. It seems every language can be used with map reduce, some have better support than others, others again are built around that concept (e.g. Go). And there are Frameworks like Apache Hadoop to support map reduce.

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