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• Performance of fopen vs stat

  - by Alex Marshall

  Hello, I'm writing several C programs for an embedded system where every bit of performance we can squeeze out will matter. Part of that is accessing log files. When determining if a file exists, is there any performance difference between using open / fopen, and stat ? I've been using stat on the assumption that it only has to do a quick check against the file system, whereas fopen would have to actually gain access to a file and manipulate internal data structures before returning. Is there any merit to this ?

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• Are there any purely functional Schemes or Lisps?

  - by nickname

  Over the past few months, I've put a lot of effort into learning (or attempting to learn) several functional programming languages. I really like math, so they have been very natural for me to use. Simply to be more specific, I have tried Common Lisp, Scheme, Haskell, OCaml, and (a little bit of) Erlang. I did not like the syntax of OCaml and do not have enough Erlang knowledge to make a judgment on it yet. Because of its consistent and beautiful (non-)syntax, I really like Scheme. However, I really do appreciate the stateless nature of purely functional programming languages such as Haskell. Haskell looks very interesting, but the amount of inconsistent and non-extendable syntax really bothered me. In the interest of preventing a Lisp vs Haskell flame war, just pretend that I can't use Haskell for some other reason. Therefore, my question is: Are there any purely functional Schemes (or Lisps in general)?

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• 'Array of arrays' in matlab?

  - by waitinforatrain

  Hey, having a wee bit of trouble. Trying to assign a variable length 1d array to different values of an array, e.g. a(1) = [1, 0.13,0.52,0.3]; a(2) = [1, 0, .268]; However, I get the error: ??? In an assignment A(I) = B, the number of elements in B and I must be the same. Error in ==> lab2 at 15 a(1) = [1, 0.13,0.52,0.3]; I presume this means that it's expecting a scalar value instead of an array. Does anybody know how to assign the array to this value? I'd rather not define it directly as a 2d array as it is for are doing solutions to different problems in a loop Edit: Got it! a(1,1:4) = [1, 0.13,0.52,0.3]; a(2,1:3) = [1, 0, .268];

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• Password reset by email without a database table

  - by jpatokal

  The normal flow for resetting a user's password by mail is this: Generate a random string and store it in a database table Email string to user User clicks on link containing string String is validated against database; if it matches, user's pw is reset However, maintaining a table and expiring old strings etc seems like a bit of an unnecessary hassle. Are there any obvious flaws in this alternative approach? Generate a MD5 hash of the user's existing password Email hash string to user User clicks on link containing string String is validated by hashing existing pw again; if it matches, user's pw is reset Note that the user's password is already stored in a hashed and salted form, and I'm just hashing it once more to get a unique but repeatable string. And yes, there is one obvious "flaw": the reset link thus generated will not expire until the user changes their password (clicks the link). I don't really see why this would be a problem though -- if the mailbox is compromised, the user is screwed anyway.

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• Error Using PDCurses: Cannot Open File Libc.C

  - by cam

  I'm getting the error: 1>LINK : fatal error LNK1104: cannot open file 'LIBC.lib' Here's my source code: #include <curses.h> int main() { initscr(); /* Start curses mode */ printw("Hello World !!!"); /* Print Hello World */ refresh(); /* Print it on to the real screen */ getch(); /* Wait for user input */ endwin(); /* End curses mode */ return 0; } I've configured the PDcurses library properly (added to Additional Include libraries, added folder to Additional Library Directories). I've looked around for a bit, and I've tried adding Libc.C to the 'Ignore Library' list, which in turn causes about 150 errors. Not sure what to do from here.

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• 'script/console test' with spork and rspec not loading the whole environment?

  - by TheDeeno

  I'm trying to load up console to interact with some of my rspec mocking helpers. I expected that running script/console test would load an env similar to when I run spec. However, this doesn't appear to be the case. It looks like spec_helper is never loaded. Or, if it is, it's not actually running through the logic because spork has polluted it a bit. In short, is there a quick and easy way to get an interactive rspec party going?

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• Nesting Patterns Algorithms / Cutting Waste Problem

  - by WedTM

  First off, I'd like to say that I'm already looking into the "Cutting Stock Problem" algorithm, however I feel that I need a bit more clarification, and possibly some help with some of the math (Not my strong point). What I need to do is have an offset pattern that causes the circle to fit in the crevasse created by having the two circular dies sitting next to each other on the previous line, like so: O O O O O O O O O O O O O O O O O I'm hoping someone can point me towards the right algorithm for this! Thanks!

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• Scrapy Not Returning Additonal Info from Scraped Link in Item via Request Callback

  - by zoonosis

  Basically the code below scrapes the first 5 items of a table. One of the fields is another href and clicking on that href provides more info which I want to collect and add to the original item. So parse is supposed to pass the semi populated item to parse_next_page which then scrapes the next bit and should return the completed item back to parse Running the code below only returns the info collected in parse If I change the return items to return request I get a completed item with all 3 "things" but I only get 1 of the rows, not all 5. Im sure its something simple, I just can't see it. class ThingSpider(BaseSpider): name = "thing" allowed_domains = ["somepage.com"] start_urls = [ "http://www.somepage.com" ] def parse(self, response): hxs = HtmlXPathSelector(response) items = [] for x in range (1,6): item = ScrapyItem() str_selector = '//tr[@name="row{0}"]'.format(x) item['thing1'] = hxs.select(str_selector")]/a/text()').extract() item['thing2'] = hxs.select(str_selector")]/a/@href').extract() print 'hello' request = Request("www.nextpage.com", callback=self.parse_next_page,meta={'item':item}) print 'hello2' request.meta['item'] = item items.append(item) return items def parse_next_page(self, response): print 'stuff' hxs = HtmlXPathSelector(response) item = response.meta['item'] item['thing3'] = hxs.select('//div/ul/li[1]/span[2]/text()').extract() return item

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• What should I grab as a development platform, an iPod or an iPad?

  - by mmr

  Hey all, I've recently gotten into the world of contract programming, and two of my clients have indicated that they'd like to do something 'trendy', like ipod touch/iphone/ipad development. I have a mac laptop (first gen macbook pro) that I'll have to upgrade to snow leopard to do the development for any of them, from what I've read. So that's already a bit of a commitment, given all the stuff I have on that laptop I'll have to make sure is recoverable from backup. My budget is limited, but I think I need to learn this skill. Which device should I get to learn this kind of development, an iPod touch or an iPad? I don't have the money for an iPhone. I think that the iPhone/iPad SDK has an emulator mode, but I like to have the device I'm going to roll out on available to make sure that everything works as I'd expect, ie, what's easily readable on a laptop screen is still readable on the touch, etc.

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• How can I share Configuration Settings across multiple projects in Visual Studio?

  - by Muneeb

  Ok I know this may be a design issue, so I would love to have remarks on that as well. I have a Visual Studio web application solution. I have three projects as UserInterface, BusinessLogic and DataAccess. I had to store some user defined settings and I created configSections in the config file. I access these configSections through classes which inherit from .NET's ConfigurationSection base class. So in short for every project I had a separate configSection and for that corresponding configSection I had a class in that project inheriting from ConfigurationSection to access the config section settings. This works all sweet. But the problem arises if there is any setting which I need to use across multiple projects. So If I need to use a setting defined in UserInterface project configSection in, let say, BusinessLogic project I have to actually make a copy of that setting in the BusinessLogic's configSection. This ends up having the same setting copied across multiple configSections. Isn't this a bit too redundant?

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• How do I configure the Python logging module in Django?

  - by mipadi

  I'm trying to configure logging for a Django app using the Python logging module. I have placed the following bit of configuration code in my Django project's settings.py file: import logging import logging.handlers import os date_fmt = '%m/%d/%Y %H:%M:%S' log_formatter = logging.Formatter(u'[%(asctime)s] %(levelname)-7s: %(message)s (%(filename)s:%(lineno)d)', datefmt=date_fmt) log_dir = os.path.join(PROJECT_DIR, "var", "log", "my_app") log_name = os.path.join(log_dir, "nyrb.log") bytes = 1024 * 1024 # 1 MB if not os.path.exists(log_dir): os.makedirs(log_dir) handler = logging.handlers.RotatingFileHandler(log_name, maxBytes=bytes, backupCount=7) handler.setFormatter(log_formatter) handler.setLevel(logging.DEBUG) logging.getLogger().setLevel(logging.DEBUG) logging.getLogger().addHandler(handler) logging.getLogger(__name__).info("Initialized logging subsystem") At startup, I get a couple Django-related messages, as well as the "Initialized logging subsystem", in the log files, but then all the log messages end up going to the web server logs (/var/log/apache2/error.log, since I'm using Apache), and use the standard log format (not the formatter I designated). Am I configuring logging incorrectly?

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• Unit testing UDP socket handling code

  - by JustJeff

  Are there any 'good' ways to cause a thread waiting on a recvfrom() call to become unblocked and return with an error? The motivation for this is to write unit tests for a system which includes a unit that reads UDP datagrams. One of the branches handles errors on the recvfrom call itself. The code isn't required to distinguish between different types of errors, it just has to set a flag. I've thought of closing the socket from another thread, or do a shutdown on it, to cause recvfrom to return with an error, but this seems a bit heavy handed. I've seen mention elsewhere that sending an over-sized packet would do it, and so set up an experiment where a 16K buffer was sent to a recvfrom waiting for just 4K, but that didn't result in an error. The recvfrom just return 4096, to indicate it had gotten that many bytes.

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• .NET Decimal = what in SQL?

  - by dmose

  What's the best data type in SQL to represent Decimal in .NET? We want to store decimal numbers with up to 9 decimal place precision and want to avoid rounding errors etc on the front end. Reading about data types, it appears using Decimal in .NET is the best option because you will not get rounding errors, although it is a bit slower than a Double. We want to carry this through down to the DB and want minimum conversion issues when moving data through the layers. Any suggestions?

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• C# "Could not find a part of the path" - Creating Local File

  - by Pyronaut

  I am trying to write to a folder that is located on my C:\ drive. I keep getting the error of : Could not find a part of the path .. etc My filepath looks basically like this : C:\WebRoot\ManagedFiles\folder\thumbs\5c27a312-343e-4bdf-b294-0d599330c42d\Image\lighthouse.jpg And I am writing to it like so : using (MemoryStream memoryStream = new MemoryStream()) { thumbImage.Save(memoryStream, ImageFormat.Jpeg); using (FileStream diskCacheStream = new FileStream(cachePath, FileMode.CreateNew)) { memoryStream.WriteTo(diskCacheStream); } memoryStream.WriteTo(context.Response.OutputStream); } Don't worry too much about the memory stream. It is just outputting it (After I save it). Since I am creating a file, I am a bit perplexed as to why it cannot find the file (Shouldn't it just write to where I tell it to, regardless?). The strange thing is, It has no issue when I'm testing it above using File.Exists. Obviously that is returning false, But it means that atleast my Filepath is semi legit. Any help is much appreciated.

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• Best implementation for MySQL replication with Rails 3?

  - by vonconrad

  We're looking at potentially setting up replication for our primary MySQL database, and while setting up the replication seems pretty straight-forward, the application implementation seems a bit murkier. My first idea would be to set up a master-slave configuration and RW-splitting, with all write queries (CREATE, INSERT, UPDATE) going to master, and all read queries (SELECT) going to slave. Having read up on it, it seems that there are essentially two options for how to implement this with our app: Using an independent middleware layer for all MySQL connections, such as MySQL proxy or DBSlayer. However, the former is in Alpha and the latter has limited documentation. Using a Ruby-based gem/plugin, such as Octopus to achieve RW-splitting in the framework. If we wanted to go with a master-slave setup, what you recommend moving forward? The other thought I've had was to use a master-master configuration, but am unsure about the implementation of such a setup. Thoughts?

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• What if I have an API method and a contoller/view method with the same name in RoR?

  - by Chad Johnson

  Suppose I want to be able to view a list of products on my site by going to /product/list. Great. So this uses my 'list' view and outputs some HTML which my web browser will render. But now suppose I want to provide a REST API to my client where they can get a list of their products. So I suppose I'd have them authenticate with oAuth and then they'd call /product/list which would return a JSON array of their products. But like I said earlier, /product/list displays an HTML web page. So, I have a conflict. What is normal practice as far as providing APIs in Rails? Should I have a subdirectory, 'api', in /app/controller, and another 'product' controller? So my client would go to /api/product/list to get a list of their products? I'm a bit new to RoR, so I don't have the best grasp of the REST functionality yet, but hopefully my question makes sense.

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• Eclipse jvm.dll error when loading

  - by Dan James Palmer

  Trying to open Eclipse after a couple of months and get this error: So I checked that folder to see if it existed, and it did: I checked my PATH Was correct and it was also correct: When this error first occurred I had 3 Java installations. JRE 7 Update 10, JDK 7 Update 7 32bit and 64 bit. I uninstall ALL and restarted my machine. Eclipse then stated, as expected that I needed a JRE or a JDK. So I downloaded and installed the latest JDK and now I get this error, despite everything appearing to be correct. Any ideas?

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• Convert mediawiki to LaTeX syntax

  - by Amit Kumar

  I need to convert mediawiki into LaTeX syntax. The formulas should stay the same, but I need to transform, for example = something = into \chapter{something}. Although this can be obtained with a bit of sed, things get a little dirty with the itemize environment, so I was wondering if a better solution can be produced. Anything that can be useful for this task ? This is the reverse of this question (graciously copied). Pandoc was the answer to that question, but probably not yet for this.

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• Database indexes - what should they be

  - by WebweaverD

  Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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• getting a gridview and dropdownlist to remember their states after navigate away and back button scr

  - by nat

  hi i have a page filling a gridview which is all working fine. the grid is basically the result of a search .. the filters for which are a number of dropdowns and a couple of textboxes the data from the grid and dropdowns are saved in the session and the whole page lives inside an updatepanel when i navigate away from the page (as it happens by clicking a link inside the grid) and then back button to it, all the droppers are back to their unselected values and the grid is nowhere to be seen.. i understand that this is because of the scriptmanager doesnt do 'standard' postbacks so the browser doesnt realise what has happened. however i have set the EnableHistory to true in the scriptmanager is there an easy way to get this to remember without dropping the updatepanel/scriptmanager? also to complicate things further the scriptmanger /updatepanel is actually in a master page. so not really sure how i can get the navigate bits to work in the scriptmanager.. clearly i am a bit confuised and any help that someone could provide would be happily received thanks nat

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• .NET Application using a native DLL (build management)

  - by moogs

  I have a .NET app that is dependent on a native DLL. I have the .NET app set as AnyCPU. In the post-build step, I plan to copy the correct native DLL from some directory (x86 or AMD64) and place it in the target path. However, this doesn't work. On a 64-bit machine, the environment variable PROCESSOR_ARCHITECTURE is "x86" in Visual Studio. My alternative right now is to create a small tool that outputs the processor architecture. This will be used by the post-build step. Is there a better alternative? (Side Note: when deploying/packaging the app, the right native DLL is copied to the right platform. But this means we have two separate release folders for x86 and AMD64, which is OK since this is for a device driver. The app is a utility tool for the driver).

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• How I do I make controls/elements move with inertia?

  - by Kris Erickson

  Modern UI's are starting to give their UI elments nice inertia when moving. Tabs slide in, page transitions, even some listboxes and scroll elments have nice inertia to them (the iphone for example). What is the best algorythm for this? It is more than just gravity as they speed up, and then slow down as they fall into place. I have tried various formulae's for speeding up to a maximum (terminal) velocity and then slowing down but nothing I have tried "feels" right. It always feels a little bit off. Is there a standard for this, or is it just a matter of playing with various numbers until it looks/feels right?

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• Apache Axis2 tried books

  - by josh

  I am looking to get my hands wet in Java Web Services. Apache CXF and Axis2 seem to be in demand a lot. I googled a bit for finding a good Axis2 book that has lot of working examples. some books like Quick Start Apache Axis 2 seem to have bad reviews on Amazon and titles like Web Services with Apache CXF and Axis2 seem to lack working examples. I want to get opinion from people who currently work with Axis2 and have read a book or two on the subject. Which is a good book for an Axis2 n00b.

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• Which language to learn C# or Salesforce.com/apex for C++ programmer

  - by polapts

  Being a C++ programmer with 7-8 years of experience, I wanted to know the market trends. When I searched a little bit I found more jobs with keyword C# than C++ or Java. I am just wondering if it is a good idea to learn C# or Java from a career perspective. Also, I read somewhere about Salesforce/apex. It was mentioned that this is something in vogue. So my question is which technology I should go for C#/Java/Salesforce(Apex) from career perspective? Thanks

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• Large Scale VHDL techniques

  - by oxinabox.ucc.asn.au

  I'm thinking about implimenting a 16 bit CPU in VHDL. A simplish CPU. ADD, MULS, NEG, BitShift, JUMP, Relitive Jump, BREQ, Relitive BREQ, i don't know somethign along these lines Probably all only working with 16bit operands. I might even cut it down and use only a single operand and a accumulator. With Some status regitsters, Carry, Zero, Neg (unless i use a Accumlator), I know how to design all the parts from logic gates, and plan to build them up from first priciples, So for my ALU I'll need to 'build' a ADDer, proably a Carry Look ahead, group adder, this adder it self is make up oa a couple of parts, wich are themselves made up of a couple of parts. Anyway, my problem is not the CPU design, or the VHDL (i know the language, more or less). It's how i should keep things organised. How should I use packages, How should I name my processes and port maps? (i've never seen the benifit of naming the port maps, or processes)

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