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  • Python - Checking for membership inside nested dict

    - by victorhooi
    heya, This is a followup questions to this one: http://stackoverflow.com/questions/2901422/python-dictreader-skipping-rows-with-missing-columns Turns out I was being silly, and using the wrong ID field. I'm using Python 3.x here. I have a dict of employees, indexed by a string, "directory_id". Each value is a nested dict with employee attributes (phone number, surname etc.). One of these values is a secondary ID, say "internal_id", and another is their manager, call it "manager_internal_id". The "internal_id" field is non-mandatory, and not every employee has one. (I've simplified the fields a little, both to make it easier to read, and also for privacy/compliance reasons). The issue here is that we index (key) each employee by their directory_id, but when we lookup their manager, we need to find managers by their "internal_id". Before, when employee.keys() was a list of internal_ids, I was using a membership check on this. Now, the last part of my if statement won't work, since the internal_ids is part of the dict values, instead of the key itself. def lookup_supervisor(manager_internal_id, employees): if manager_internal_idis not None and manager_internal_id!= "" and manager_internal_id in employees.keys(): return (employees[manager_internal_id]['mail'], employees[manager_internal_id]['givenName'], employees[manager_internal_id]['sn']) else: return ('Supervisor Not Found', 'Supervisor Not Found', 'Supervisor Not Found') So the first question is, how do I check whether the manager_internal_id is present in the dict's values. I've tried substituting employee.keys() with employee.values(), that didn't work. Also, I'm hoping for something a little more efficient, not sure if there's a way to get a subset of the values, specifically, all the entries for employees[directory_id]['internal_id']. Hopefully there's some Pythonic way of doing this, without using a massive heap of nested for/if loops. My second question is, how do I then cleanly return the required employee attributes (mail, givenname, surname etc.). My for loop is iterating over each employee, and calling lookup_supervisor. I'm feeling a bit stupid/stumped here. def tidy_data(employees): for directory_id, data in employees.items(): # We really shouldnt' be passing employees back and forth like this - hmm, classes? data['SupervisorEmail'], data['SupervisorFirstName'], data['SupervisorSurname'] = lookup_supervisor(data['manager_internal_id'], employees) Thanks in advance =), Victor

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  • Naive Bayesian classification (spam filtering) - Doubt in one calculation? Which one is right? Plz c

    - by Microkernel
    Hi guys, I am implementing Naive Bayesian classifier for spam filtering. I have doubt on some calculation. Please clarify me what to do. Here is my question. In this method, you have to calculate P(S|W) - Probability that Message is spam given word W occurs in it. P(W|S) - Probability that word W occurs in a spam message. P(W|H) - Probability that word W occurs in a Ham message. So to calculate P(W|S), should I do (1) (Number of times W occuring in spam)/(total number of times W occurs in all the messages) OR (2) (Number of times word W occurs in Spam)/(Total number of words in the spam message) So, to calculate P(W|S), should I do (1) or (2)? (I thought it to be (2), but I am not sure, so plz clarify me) I am refering http://en.wikipedia.org/wiki/Bayesian_spam_filtering for the info by the way. I got to complete the implementation by this weekend :( Thanks and regards, MicroKernel :) @sth: Hmm... Shouldn't repeated occurrence of word 'W' increase a message's spam score? In the your approach it wouldn't, right?. Lets take a scenario and discuss... Lets say, we have 100 training messages, out of which 50 are spam and 50 are Ham. and say word_count of each message = 100. And lets say, in spam messages word W occurs 5 times in each message and word W occurs 1 time in Ham message. So total number of times W occuring in all the spam message = 5*50 = 250 times. And total number of times W occuring in all Ham messages = 1*50 = 50 times. Total occurance of W in all of the training messages = (250+50) = 300 times. So, in this scenario, how do u calculate P(W|S) and P(W|H) ? Naturally we should expect, P(W|S) P(W|H)??? right. Please share your thought...

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  • Unable to register achievements

    - by abe
    I've been unable to register any achievements. I keep getting the following: {"error":{"message":"(#3502) Object at achievement URL is not of type game.achievement","type":"OAuthException","code":3502}} When I run my URL through the linter, I get: Open Graph Warnings That Should Be Fixed Inferred Property: The 'og:url' property should be explicitly provided, even if a value can be inferred from other tags. Inferred Property: The 'og:title' property should be explicitly provided, even if a value can be inferred from other tags. Although when I load the URL myself I clearly see those set in the meta tags. My HTML looks like: <html> <head prefix="og: http://ogp.me/ns# fb: http://ogp.me/ns/fb# game: http://ogp.me/ns/game#"> <meta property="fb:app_id" content="<MY_APP_ID>" /> <meta property="og:type" content="game.achievement" /> <meta property="og:url" content="http://<MY_DOMAIN>/ach10.html" /> <meta property="og:title" content="Title" /> <meta property="og:description" content="Description" /> <meta property="og:image" content="http://placekitten.com/g/200/300" /> </head> <body> Hmm.. </body> </html> Also interesting, is the graph API sees it as: { "url": "http://<MY_DOMAIN>/ach10.html", "type": "website", "title": "http://<MY_DOMAIN>/ach10.html", "updated_time": "2012-03-09T19:49:14+0000", "id": "<ID>" } And the scraped URL returns nothing ... anyone have any ideas? I've also tried adding the Game Achievement object in the Open Graph settings and every combination of Sandbox Mode/Social Discovery enabled and disabled.

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  • Which text margin does SWT Table use when drawing text?

    - by Zordid
    I got a relatively easy question - but I cannot find anything anywhere to answer it. I use a simple SWT table widget in my application that displays only text in the cells. I got an incremental search feature and want to highlight text snippets in all cells if they match. So when typing "a", all "a"s should be highlighted. To get this, I add an SWT.EraseItem listener to interfere with the background drawing. If the current cell's text contains the search string, I find the positions and calculate relative x-coordinates within the text using event.gc.stringExtent - easy. With that I just draw rectangles "behind" the occurrences. Now, there's a flaw in this. The table does not draw the text without a margin, so my x coordinate does not really match - it is slightly off by a few pixels! But how many?? Where do I retrieve the cell's text margins that table's own drawing will use? No clue. Cannot find anything. :-( Bonus question: the table's draw method also shortens text and adds "..." if it does not fit into the cell. Hmm. My occurrence finder takes the TableItem's text and thus also tries to mark occurrences that are actually not visible because they are consumed by the "...". How do I get the shortened text and not the "real" text within the EraseItem draw handler? Thanks!

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  • List of fonts installed by default in versions of Windows?

    - by Ricket
    I've been seeing more and more websites using fancy antialiased fonts. Every time I hit one, I think to myself "hmm, what web-safe font is that?" - but after looking at the CSS I typically find some font name in quotes, like "Palatino Linotype". Obviously not web-safe, but according to the Wikipedia article, "Palatino Linotype is shipped with Windows 2000 or later, and Microsoft Office Professional Edition 2003." So that covers what, 95% of users that might visit your website? And thanks to the power of CSS, the website can fallback to a similar generic font typename such as 'serif' for non-Windows users with a line like this: font: 16px/20px "Palatino Linotype", serif; Awesome! I want to start using fancy fonts! Is there a set of lists out there, of the fonts that are preinstalled by default in Windows 98, 2000, NT, ME, XP, 2003, etc., and maybe for the Mac OSX versions and various Linux distributions as well? It would be a great reference for picking web font faces! (if not, someone should compile it!) I had never before heard of Palatino Linotype and I want to know what other fonts have existed since old Windows versions that I've never known about!

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  • Haskell Cons Operator (:)

    - by Carson Myers
    I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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  • C# XNA: What can cause SpriteBatch.End() to throw a NRE?

    - by Rosarch
    I don't understand what I'm doing wrong here: public void Draw(GameTime gameTime) // in ScreenManager { SpriteBatch.Begin(SpriteBlendMode.AlphaBlend); for (int i = 0; i < Screens.Count; i++) { if (Screens[i].State == Screen.ScreenState.HIDDEN) continue; Screens[i].Draw(gameTime); } SpriteBatch.End(); // null ref exception } SpriteBatch itself is not null. Some more context: public class MasterEngine : Microsoft.Xna.Framework.Game { public MasterEngine() { graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); // ... spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); screenManager = new ScreenManager(assets, gameEngine, graphicsDeviceManager.GraphicsDevice, spriteBatch); } //... protected override void Draw(GameTime gameTime) { screenManager.Draw(gameTime); // calls the problematic method base.Draw(gameTime); } } Am I failing to initialize something properly? UPDATE: As an experiment, I tried this to the constructor of MasterEngine: spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); spriteBatch.Begin(); spriteBatch.DrawString(assets.GetAsset<SpriteFont>("calibri"), "ftw", new Vector2(), Color.White); spriteBatch.End(); This does not cause a NRE. hmm.... UPDATE 2: This does cause an NRE: protected override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.End(); // boned here //screenManager.Draw(gameTime); base.Draw(gameTime); }

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  • XNA: What can cause SpriteBatch.End() to throw a NRE?

    - by Rosarch
    I don't understand what I'm doing wrong here: public void Draw(GameTime gameTime) // in ScreenManager { SpriteBatch.Begin(SpriteBlendMode.AlphaBlend); for (int i = 0; i < Screens.Count; i++) { if (Screens[i].State == Screen.ScreenState.HIDDEN) continue; Screens[i].Draw(gameTime); } SpriteBatch.End(); // null ref exception } SpriteBatch itself is not null. Some more context: public class MasterEngine : Microsoft.Xna.Framework.Game { public MasterEngine() { graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); // ... spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); screenManager = new ScreenManager(assets, gameEngine, graphicsDeviceManager.GraphicsDevice, spriteBatch); } //... protected override void Draw(GameTime gameTime) { screenManager.Draw(gameTime); // calls the problematic method base.Draw(gameTime); } } Am I failing to initialize something properly? UPDATE: As an experiment, I tried this to the constructor of MasterEngine: spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); spriteBatch.Begin(); spriteBatch.DrawString(assets.GetAsset<SpriteFont>("calibri"), "ftw", new Vector2(), Color.White); spriteBatch.End(); This does not cause a NRE. hmm.... UPDATE 2: This does cause an NRE: protected override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.End(); // boned here //screenManager.Draw(gameTime); base.Draw(gameTime); }

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  • form submit button moves cutting image

    - by flavour404
    Hi I have a submit button and am styling it using the following css: .subm { background-color:Transparent; background-image:url(Images/Button_Send.png); background-repeat:no-repeat; width:82px; height:30px; display:block; border:none; outline:none; overflow:visible;} .subm:hover { background-color:Transparent; background-image:url(Images/Button_Send_Over.png); background-repeat:no-repeat; width:82px; height:30px; display:block; border:none; outline:none; overflow:visible; } Here is the html: <input type="submit" class="subm" value="" /> Nothing surprising. However, what annoys me is that when the submit button is clicked in IE it moves the image up a couple of pixels cutting them off which makes it look, hmm, good word, 'naff.' How can I compensate or stop this? I have tried expanding the image and leaving a couple of blank pixels at the top but it still does the same thing! Thanks R.

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  • Template trick to optimize out allocations

    - by anon
    I have: struct DoubleVec { std::vector<double> data; }; DoubleVec operator+(const DoubleVec& lhs, const DoubleVec& rhs) { DoubleVec ans(lhs.size()); for(int i = 0; i < lhs.size(); ++i) { ans[i] = lhs[i]] + rhs[i]; // assume lhs.size() == rhs.size() } return ans; } DoubleVec someFunc(DoubleVec a, DoubleVec b, DoubleVec c, DoubleVec d) { DoubleVec ans = a + b + c + d; } Now, in the above, the "a + b + c + d" will cause the creation of 3 temporary DoubleVec's -- is there a way to optimize this away with some type of template magic ... i.e. to optimize it down to something equivalent to: DoubleVec ans(a.size()); for(int i = 0; i < ans.size(); i++) ans[i] = a[i] + b[i] + c[i] + d[i]; You can assume all DoubleVec's have the same # of elements. The high level idea is to have do some type of templateied magic on "+", which "delays the computation" until the =, at which point it looks into itself, goes hmm ... I'm just adding thes numbers, and syntheizes a[i] + b[i] + c[i] + d[i] ... instead of all the temporaries. Thanks!

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  • Modify passed, nested dict/list

    - by Gerenuk
    I was thinking of writing a function to normalize some data. A simple approach is def normalize(l, aggregate=sum, norm_by=operator.truediv): aggregated=aggregate(l) for i in range(len(l)): l[i]=norm_by(l[i], aggregated) l=[1,2,3,4] normalize(l) l -> [0.1, 0.2, 0.3, 0.4] However for nested lists and dicts where I want to normalize over an inner index this doesnt work. I mean I'd like to get l=[[1,100],[2,100],[3,100],[4,100]] normalize(l, ?? ) l -> [[0.1,100],[0.2,100],[0.3,100],[0.4,100]] Any ideas how I could implement such a normalize function? Maybe it would be crazy cool to write normalize(l[...][0]) Is it possible to make this work?? Or any other ideas? Also not only lists but also dict could be nested. Hmm... EDIT: I just found out that numpy offers such a syntax (for lists however). Anyone know how I would implement the ellipsis trick myself?

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  • LINQ extention SelectMany in 3.5 vs 4.0?

    - by Moberg
    Hi When I saw Darins suggestion here .. IEnumerable<Process> processes = new[] { "process1", "process2" } .SelectMany(Process.GetProcessesByName); ( http://stackoverflow.com/questions/3059667/process-getprocessesbyname/3059733#3059733 ) .. I was a bit intrigued and I tried it in VS2008 with .NET 3.5 - and it did not compiling unless I changed it to .. IEnumerable<Process> res = new string[] { "notepad", "firefox", "outlook" } .SelectMany(s => Process.GetProcessesByName(s)); Having read some Darins answers before I suspected that it was me that were the problem, and when I later got my hands on a VS2010 with.NET 4.0 - as expected - the original suggestion worked beautifully. My question is : What have happend from 3.5 to 4.0 that makes this (new syntax) possible? Is it the extentionmethods that have been extended(hmm) or new rules for lambda syntax or? I've tried to search but my google-fu was not strong enough. Please forgive if the question is a bit naive and note that I've taged it as beginner :)

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  • Use a foreign key mapping to get data from the other table using Python and SQLAlchemy.

    - by Az
    Hmm, the title was harder to formulate than I thought. Basically, I've got these simple classes mapped to tables, using SQLAlchemy. I know they're missing a few items but those aren't essential for highlighting the problem. class Customer(object): def __init__(self, uid, name, email): self.uid = uid self.name = name self.email = email def __repr__(self): return str(self) def __str__(self): return "Cust: %s, Name: %s (Email: %s)" %(self.uid, self.name, self.email) The above is basically a simple customer with an id, name and an email address. class Order(object): def __init__(self, item_id, item_name, customer): self.item_id = item_id self.item_name = item_name self.customer = None def __repr__(self): return str(self) def __str__(self): return "Item ID %s: %s, has been ordered by customer no. %s" %(self.item_id, self.item_name, self.customer) This is the Orders class that just holds the order information: an id, a name and a reference to a customer. It's initialised to None to indicate that this item doesn't have a customer yet. The code's job will assign the item a customer. The following code maps these classes to respective database tables. # SQLAlchemy database transmutation engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() customers_table = Table('customers', metadata, Column('uid', Integer, primary_key=True), Column('name', String), Column('email', String) ) orders_table = Table('orders', metadata, Column('item_id', Integer, primary_key=True), Column('item_name', String), Column('customer', Integer, ForeignKey('customers.uid')) ) metadata.create_all(engine) mapper(Customer, customers_table) mapper(Orders, orders_table) Now if I do something like: for order in session.query(Order): print order I can get a list of orders in this form: Item ID 1001: MX4000 Laser Mouse, has been ordered by customer no. 12 What I want to do is find out customer 12's name and email address (which is why I used the ForeignKey into the Customer table). How would I go about it?

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  • How to push further as a programmer?

    - by MaXX
    For the last, hmm, 6 months I've been reading into Programming in C, I got myself K&Rv2, BEEJ's socket guide, Expert C programming, Linux Systems Programming, the ISO/IEC 9899:1999 specification (real, and not draft). After receiving them from Amazon, I got Linux installed, and got to it. I'm done with K&R, about halfway through Expert C Programming, but still feel weak as a programmer, I'm sure it takes much more than 6 months of reading to become truly skilled, but my question is this: I've done all the exercises in K&Rv2 (in chapter 1) and some in other chapters, most of which are generally really boring. How do I lift my skills, and become truly great? I've invested money, time and a general lifestyle for something I truly desire, but I'm not sure how exactly to achieve it. Could someone explain to me, perhaps if I need to continuously code, what exactly I'm to code? I'm pretty sure, coding up hello world programs isn't going to teach me any more than I already know about anything. A friend of mine said "read" (with emphasis on read) a man page a day, but reading is all I do, I want to do, but I'm not sure what! I'm interested in security, but I'm not sure as a novice what to code that would be considered enough. Ah, I hope you don't delete this paste :) Thanks

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  • C# XNA: What can cause SpriteBatch.End() to throw a NPE?

    - by Rosarch
    I don't understand what I'm doing wrong here: public void Draw(GameTime gameTime) // in ScreenManager { SpriteBatch.Begin(SpriteBlendMode.AlphaBlend); for (int i = 0; i < Screens.Count; i++) { if (Screens[i].State == Screen.ScreenState.HIDDEN) continue; Screens[i].Draw(gameTime); } SpriteBatch.End(); // null ref exception } SpriteBatch itself is not null. Some more context: public class MasterEngine : Microsoft.Xna.Framework.Game { public MasterEngine() { graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); // ... spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); screenManager = new ScreenManager(assets, gameEngine, graphicsDeviceManager.GraphicsDevice, spriteBatch); } //... protected override void Draw(GameTime gameTime) { screenManager.Draw(gameTime); // calls the problematic method base.Draw(gameTime); } } Am I failing to initialize something properly? UPDATE: As an experiment, I tried this to the constructor of MasterEngine: spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); spriteBatch.Begin(); spriteBatch.DrawString(assets.GetAsset<SpriteFont>("calibri"), "ftw", new Vector2(), Color.White); spriteBatch.End(); This does not cause a NRE. hmm....

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  • How can I install things in Linux with *no yum* and *no wget*?

    - by e9t
    I'm a newbie to Linux (that mainly uses Windows and Mac OS X) needing some advice. I was trying to install git on a Linux machine today, and encountered some problems: Not knowing the version of the installed OS, I've opened the /proc/version file which said: Linux version 2.6.9-42.0.2.ELsmp ([email protected]) (gcc version 3.4.6 20060404 (Red Hat 3.4.6-3)) #1 SMP Thu Aug 17 17:57:31 EDT 2006 Then, as written in the git documents (http://git-scm.com/download/linux), I assumed I could use the yum install git command for Fedora, but got the following result. [root@myserver ~]# yum install git -bash: yum: command not found So I tried installing yum using wget, but wasn't so lucky. [root@myserver ~]# wget http://linux.duke.edu/projects/yum/download/2.0/yum-2.0.7.tar.gz -bash: wget: command not found I googled and found this page and this page, so tried installing yum with rpm, but only got a result full of question marks. (Possibly an encoding problem, hmm...) [root@myserver ~]# rpm -Uvh http://www.eomy.net/linux/install-yum-x86_64/wget-1.10.2-0.40E.x86_64.rpm http://www.eomy.net/linux/install-yum-x86_64/wget-1.10.2-0.40E.x86_64.rpm(??)?? ?????? ?: /var/tmp/rpm-xfer.TbuAOu: V3 DSA signature: NOKEY, key ID 443e1821 ???.. ########################################### [100%] wget-1.10.2-0.40E U???????g??????? wget-1.10.2-0.40E???? ??g??/usr/bin/wget ?? wget-1.10.2-0.40E U?????? ???? wget-1.10.2-0.40E???? ??g??/usr/share/man/man1/wget.1.gz ?? wget-1.10.2-0.40E U?????? ???? [root@myserver ~]# Finally, when I typed rpm --version in the terminal, I got the below results. [root@myserver ~]# rpm --version RPM ???? - 4.3.3 I would like to know what I can do or possibly try now. Is it not possible to wget or yum anything in my situation? Or is there any magical tool like homebrew (http://mxcl.github.com/homebrew/) that I can use? Any comments or advice would be appreciated. Thanks in advance!

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  • how to notify a program of another program? dll? directory? path?

    - by Brady Trainor
    I am trying to experiment with GNUS email in Emacs, in Windows (EDIT: x64 bit). I've got it to work in Ubuntu, but struggling with it in Windows. From http://www.gnu.org/software/emacs/manual/html_mono/emacs-gnutls.html#Help-For-Users I read in second paragraph: This is a little bit trickier on the W32 (Windows) platform, but if you have the GnuTLS DLLs (available from http://sourceforge.net/projects/ezwinports/files/ thanks to Eli Zaretskii) in the same directory as Emacs, you should be OK. I have downloaded and unzipped the gnutls-3.0.9-w32-bin package, but am not sure what to do with it. I have tried putting it in Program Files (x86), which is "the same directory as Emacs". I have tried putting it in the emacs-24.3 folder. I consider merging all the folders in between the two, but am hesitant as that seems a difficult troubleshoot attempt compared to my knowledge on these matters. I think Emacs needs to somehow see the gnutls binaries and/or dlls. My knowledge is limited on this. I've also struggled to understand PATHs for sometime now, and am not sure if that approach is relevant here. FYI, the emacs directory contains folders labeled bin, etc, info, leim, lisp and site-lisp. The gnutls directory contains folder labeled bin, include, lib and share. Hmm, now I'm finding lots of links on adding paths. Still, I'm skeptical that I would only add gnutls.exe path, as it seems the dlls are needed. Some additional data for Ramhound's first comment I have been attempting the (require 'gnutls) route. This seems to be the most relevant parts in the log: Opening connection to imap.gmail.com via tls... gnutls.c: [1] (Emacs) GnuTLS library not found Opening TLS connection to `imap.gmail.com'... Opening TLS connection with `gnutls-cli --insecure -p 993 imap.gmail.com'...failed Opening TLS connection with `gnutls-cli --insecure -p 993 imap.gmail.com --protocols ssl3'...failed Opening TLS connection with `openssl s_client -connect imap.gmail.com:993 -no_ssl2 -ign_eof'...failed Opening TLS connection to `imap.gmail.com'...failed I am not sure what "in stallion" means. Emacs seems to have installed itself in program files (x86), so I assume it is 32 bit. I can try and figure out how to double check, but did not realize I would get such fast response time, and am headed out right now. I will try merging the files later tonight?

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  • How to reset mysql's replication settings completely, without reinstalling it?

    - by user38060
    I set up mysql replication by adding references to binlogs, relay logs etc in my.cnf restarted mysql, it worked. I wanted to change it so I deleted all binlog related files including log-bin.index, removed binlog statements from my.cnf restarted server, works set master to '', purge master logs since now(), reset slave, stop slave, stop master. now, to set up replication again, I added binlog statements to the server. But then I hit this problem when restarting with: sudo mysqld (the only way to see mysql's startup errors) I get this error: /usr/sbin/mysqld: File '/etc/mysql/var/log-bin.index' not found (Errcode: 13) Because indeed, this file does not exist! (I deleted it, while trying to set up a new replication system) Hmm, if I change the config line to: log-bin-index = log-bin.index I get a different error: [ERROR] Can't generate a unique log-filename /etc/mysql/var/bin.(1-999) [ERROR] MSYQL_BIN_LOG::open failed to generate new file name. [ERROR] Aborting The first time I set up replication on this system, I didn't need to create this file. I did the same thing - added references to a previously non-existing file, and mysql created it. Same with relay logs, etc. I don't know why mysql insists on trying to read the old folder. Should I just reinstall the whole package again? That seems like overkill. my my.cnf: [client] port = 3306 socket = /var/run/mysqld/mysqld.sock [mysqld_safe] socket = /var/run/mysqld/mysqld.sock nice = 0 [mysqld] user = mysql socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp skip-external-locking bind-address = IP key_buffer = 16M max_allowed_packet = 16M thread_stack = 192K thread_cache_size = 8 myisam-recover = BACKUP table_cache = 64 sort_buffer =64K net_buffer_length =2K query_cache_limit = 1M query_cache_size = 16M slow_query_log_file = /etc/mysql/var/mysql-slow.log long_query_time = 1 log-queries-not-using-indexes expire_logs_days = 10 max_binlog_size = 100M server-id = 3 log-bin = /etc/mysql/var/bin.log log-slave-updates log-bin-index = /etc/mysql/var/log-bin.index log-error = /etc/mysql/var/error.log relay-log = /etc/mysql/var/relay.log relay-log-info-file = /etc/mysql/var/relay-log.info relay-log-index = /etc/mysql/var/relay-log.index auto_increment_increment = 10 auto_increment_offset = 3 master-host = HOST master-user = USER master-password=PWD replicate-do-db = DBNAME collation_server=utf8_unicode_ci character_set_server=utf8 skip-character-set-client-handshake [mysqldump] quick quote-names max_allowed_packet = 16M [mysql] #no-auto-rehash [myisamchk] key_buffer_size = 16M sort_buffer_size = 8M [mysqlhotcopy] interactive-timeout !includedir /etc/mysql/conf.d/ Update: Changing all the /etc/mysql/var/xxx paths in binlog & relay log statements to local has somehow solved the problem. I thought it was apparmor causing it at first, but when I added /etc/mysql/* rw, to apparmor's config and restarted it, it still couldn't read the full path.

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  • DVD ROM is not working

    - by Cyril N.
    (note: I don't know in which StackExchange site to put this question, I'll thank the moderator that will move it to a more appropriate place, if there is a S.E. available for my question). I have a DVD RW drive that is well listed in the bios, and if no CD is in, it is also present in the "My Computer" of my Fedora 16. But when I put a disc on it, the icon disapear from "My Computer", and I can not do anything with this ! (Like erasing a RW disc). I'd like to boot a Fedora 17 Live CD image. I burned it on an other computer but when I try to run it in bios, nothing is done and I'm redirected to Grub of my HD. The command cdrecord -scanbus shows this : wodim: Warning: controller returns wrong size for CD capabilities page. wodim: Cannot get CD capabilities data. 6,1,0 601) 'HD-DT%ST' 'DVD%RAM G@22NP20' '1&04' Removable CD-ROM And when I try to mount manually the disc, I got this error : mount: block device /dev/sr0 is write-protected, mounting read-only mount: /dev/sr0: can't read superblock Here's a paste of dmesg | grep sr0 : [ 5.161265] sr0: scsi-1 drive [ 5.161621] sr 6:0:1:0: Attached scsi CD-ROM sr0 [ 834.545978] sr0: Hmm, seems the drive doesn't support multisession CD's [ 841.731194] sr0: CDROM (ioctl) error, command: Get configuration 46 00 00 00 00 00 00 00 20 00 [ 842.021640] sr 6:0:1:0: [sr0] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 842.021652] sr 6:0:1:0: [sr0] Sense Key : Aborted Command [current] [ 842.021662] sr 6:0:1:0: [sr0] Add. Sense: No additional sense information [ 842.021672] sr 6:0:1:0: [sr0] CDB: Read(10): 28 00 00 00 00 00 00 00 02 00 [ 842.021688] end_request: I/O error, dev sr0, sector 0 [ 842.021697] Buffer I/O error on device sr0, logical block 0 [ 842.023715] sr 6:0:1:0: [sr0] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 843.048203] sr 6:0:1:0: [sr0] Sense Key : Aborted Command [current] [ 843.048211] sr 6:0:1:0: [sr0] Add. Sense: No additional sense information [ 843.048219] sr 6:0:1:0: [sr0] CDB: Read(10): 28 00 00 00 00 00 00 00 01 00 [ 843.048234] end_request: I/O error, dev sr0, sector 0 [ 843.048274] EXT4-fs (sr0): unable to read superblock [ 843.063155] sr0: CDROM (ioctl) error, command: Get configuration 46 00 00 00 00 00 00 00 20 00 [ 843.075904] sr0: CDROM (ioctl) error, command: Get configuration 46 00 00 00 00 00 00 00 20 00 [ 843.220512] sr 6:0:1:0: [sr0] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 843.220522] sr 6:0:1:0: [sr0] Sense Key : Aborted Command [current] [ 843.220530] sr 6:0:1:0: [sr0] Add. Sense: No additional sense information [ 843.220538] sr 6:0:1:0: [sr0] CDB: Read(10): 28 00 00 00 00 00 00 00 01 00 [ 843.220553] end_request: I/O error, dev sr0, sector 0 [ 843.220609] FAT-fs (sr0): unable to read boot sector The lines from Sense Key .. (line 6) to DRIVER_SENSE (line 11) are repeating a lot. I then changed my DVD player with an other spare one I had, and the disc didn't boot neither. I then changed the IDE cable, but still no success. What can I do to make it work? Thanks for your help.

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  • SQL SERVER – Service Broker and CAP_CPU_PERCENT – Limiting SQL Server Instances to CPU Usage

    - by pinaldave
    I have mentioned several times on this blog that the best part of blogging is the questions I receive from readers. They are often very interesting. The questions from readers give me a good idea what other readers might be thinking as well. After reading my earlier article Simple Example to Configure Resource Governor – Introduction to Resource Governor – I received an email from a reader and we exchanged a few emails. After exchanging emails we both figured out what is going on. It was indeed interesting and reader suggested to that I should blog about it.  I asked for permission to publish his name but he does not like the attention so we will just call him Jeff. I have converted our emails into chat for easy consumption. Jeff: Your script does not work at all. I think either there is a bug in SQL Server. Pinal: Would you please explain in detail? Jeff: Your code does not limit the CPU usage? Pinal: How did you measure it? Jeff: Well, we have third party tools for it but let us say I have limited the resources for Reporting Services and used your script described in your blog. After that I ran only reporting service workload the CPU is still used more than 100% and it is not limited to 30% as described in your script. Clearly something is wrong somewhere. Pinal: Did you say you ONLY ran reporting server load? Jeff: Yeah, to validate I ran ONLY reporting server load and CPU did not throttle at 30% as per your script. Pinal: Oh! I get it here is the answer - CAP_CPU_PERCENT = 30. Use it. Jeff: What is that, I think your earlier script says it will throttle the Reporting Service workload and Application/OLTP workload and balance it. Pinal: Exactly, that is correct. Jeff: You need to write more in email buddy! Just like your blogs, your answers do not make sense! No Offense! Pinal: Hmm…feedback well taken. Let me try again. In SQL Server 2012 there are a few enhancements with regards to SQL Server Resource Governor. One of the enhancement is how the resources are allocated. Let me explain you with examples. Configuration: [Read Earlier Post] Reporting Workload: MIN_CPU_PERCENT=0, MAX_CPU_PERCENT=30 Application/OLTP Workload: MIN_CPU_PERCENT=50, MAX_CPU_PERCENT=100 Example 1: If there is only Reporting Workload on the server: SQL Server will not limit usage of CPU to only 30% workload but SQL Server instance will use all available CPU (if needed). In another word in this scenario it will use more than 30% CPU. Example 2: If there is Reproting Workload and heavy Application/OLTP workload: SQL Server will allocate a maximum of 30% CPU resources to Reporting Workload and allocate remaining resources to heavy application/OLTP workload. The reason for this enhancement is for better utilization of the resources. Let us think, if there is only single workload, which we have limited to max CPU usage to 30%. The other unused available CPU resources is now wasted. In this situation SQL Server allows the workload to use more than 30% resources leading to overall improved/optimized performance. However, in the case of multiple workload where lots of resources are needed the limits specified in MAX_CPU_PERCENT are acknowledged. Example 3: If there is a situation where the max CPU workload has to be enforced: This is a very interesting scenario, in the case when the max CPU workload has to be enforced irrespective of the workload and enhanced algorithm, the keyword CAP_CPU_PERCENT is essential. It specifies a hard cap on the CPU bandwidth that all requests in the resource pool will receive. It will never let CPU usage for reporting workload to go over 30% in our case. You can use the key word as follows: -- Creating Resource Pool for Report Server CREATE RESOURCE POOL ReportServerPool WITH ( MIN_CPU_PERCENT=0, MAX_CPU_PERCENT=30, CAP_CPU_PERCENT=40, MIN_MEMORY_PERCENT=0, MAX_MEMORY_PERCENT=30) GO Notice that there is MAX_CPU_PERCENT=30 and CAP_CPU_PERCENT=40, what it means is that when SQL Server Instance is under heavy load under different workload it will use the maximum CPU at 30%. However, when the SQL Server instance is not under workload it will go over the 30% limit. However, as CAP_CPU_PERCENT is set to 40, it will not go over 40% in any case by limiting the usage of CPU. CAP_CPU_PERCENT puts a hard limit on the resources usage by workload. Jeff: Nice Pinal, you should blog about it. [A day passes by] Pinal: Jeff, it is done! Click here to read it. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Service Broker

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  • F# for the C# Programmer

    - by mbcrump
    Are you a C# Programmer and can’t make it past a day without seeing or hearing someone mention F#?  Today, I’m going to walk you through your first F# application and give you a brief introduction to the language. Sit back this will only take about 20 minutes. Introduction Microsoft's F# programming language is a functional language for the .NET framework that was originally developed at Microsoft Research Cambridge by Don Syme. In October 2007, the senior vice president of the developer division at Microsoft announced that F# was being officially productized to become a fully supported .NET language and professional developers were hired to create a team of around ten people to build the product version. In September 2008, Microsoft released the first Community Technology Preview (CTP), an official beta release, of the F# distribution . In December 2008, Microsoft announced that the success of this CTP had encouraged them to escalate F# and it is now will now be shipped as one of the core languages in Visual Studio 2010 , alongside C++, C# 4.0 and VB. The F# programming language incorporates many state-of-the-art features from programming language research and ossifies them in an industrial strength implementation that promises to revolutionize interactive, parallel and concurrent programming. Advantages of F# F# is the world's first language to combine all of the following features: Type inference: types are inferred by the compiler and generic definitions are created automatically. Algebraic data types: a succinct way to represent trees. Pattern matching: a comprehensible and efficient way to dissect data structures. Active patterns: pattern matching over foreign data structures. Interactive sessions: as easy to use as Python and Mathematica. High performance JIT compilation to native code: as fast as C#. Rich data structures: lists and arrays built into the language with syntactic support. Functional programming: first-class functions and tail calls. Expressive static type system: finds bugs during compilation and provides machine-verified documentation. Sequence expressions: interrogate huge data sets efficiently. Asynchronous workflows: syntactic support for monadic style concurrent programming with cancellations. Industrial-strength IDE support: multithreaded debugging, and graphical throwback of inferred types and documentation. Commerce friendly design and a viable commercial market. Lets try a short program in C# then F# to understand the differences. Using C#: Create a variable and output the value to the console window: Sample Program. using System;   namespace ConsoleApplication9 {     class Program     {         static void Main(string[] args)         {             var a = 2;             Console.WriteLine(a);             Console.ReadLine();         }     } } A breeze right? 14 Lines of code. We could have condensed it a bit by removing the “using” statment and tossing the namespace. But this is the typical C# program. Using F#: Create a variable and output the value to the console window: To start, open Visual Studio 2010 or Visual Studio 2008. Note: If using VS2008, then please download the SDK first before getting started. If you are using VS2010 then you are already setup and ready to go. So, click File-> New Project –> Other Languages –> Visual F# –> Windows –> F# Application. You will get the screen below. Go ahead and enter a name and click OK. Now, you will notice that the Solution Explorer contains the following: Double click the Program.fs and enter the following information. Hit F5 and it should run successfully. Sample Program. open System let a = 2        Console.WriteLine a As Shown below: Hmm, what? F# did the same thing in 3 lines of code. Show me the interactive evaluation that I keep hearing about. The F# development environment for Visual Studio 2010 provides two different modes of execution for F# code: Batch compilation to a .NET executable or DLL. (This was accomplished above). Interactive evaluation. (Demo is below) The interactive session provides a > prompt, requires a double semicolon ;; identifier at the end of a code snippet to force evaluation, and returns the names (if any) and types of resulting definitions and values. To access the F# prompt, in VS2010 Goto View –> Other Window then F# Interactive. Once you have the interactive window type in the following expression: 2+3;; as shown in the screenshot below: I hope this guide helps you get started with the language, please check out the following books for further information. F# Books for further reading   Foundations of F# Author: Robert Pickering An introduction to functional programming with F#. Including many samples, this book walks through the features of the F# language and libraries, and covers many of the .NET Framework features which can be leveraged with F#.       Functional Programming for the Real World: With Examples in F# and C# Authors: Tomas Petricek and Jon Skeet An introduction to functional programming for existing C# developers written by Tomas Petricek and Jon Skeet. This book explains the core principles using both C# and F#, shows how to use functional ideas when designing .NET applications and presents practical examples such as design of domain specific language, development of multi-core applications and programming of reactive applications.

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  • Justifiable Perks.

    - by Phil Factor
        I was once the director of a start-up IT Company, and had the task of recruiting a proportion of the management team. As my background was in IT management, I was rather more familiar with recruiting Geeks for technology jobs, but here, one of my early tasks was interviewing a Marketing Director.  The small group of financiers had suggested a rather strange Irishman called  Halleran.  From my background in City of London dealing-rooms, I was slightly unprepared for the experience of interviewing anyone wearing a pink suit. Many of my older City colleagues would have required resuscitation after seeing his white leather shoes. However, nobody will accuse me of prejudging an interviewee. After all, many Linux experts who I’ve come to rely on have appeared for interview dressed as hobbits. In fact, the interview went well, and we had even settled his salary.  I was somewhat unprepared for the coda.    ‘And I will need to be provided with a Ferrari  by the company.’    ‘Hmm. That seems reasonable.’    Initially, he looked startled, and then a slow smile of victory spread across his face.    ‘What colour would you like?’ I asked genially.    ‘It has to be red.’ He looked very earnest on this point.    ‘Fine. I have to go past Hamleys on the way home this evening, so I’ll pick one up then for you.’    ‘Er.. Hamley’s is a toyshop, not a Ferrari Dealership.’    I stared at him in bafflement for a few seconds. ‘You’re not seriously asking for a real Ferrari are you?’     ‘Well, yes. Not for my own sake, you understand. I’d much prefer a simple run-about, but my position demands it. How could I maintain the necessary status in the office without one? How could I do my job in marketing when my grey Datsun was all too visible in the car Park? It is a tool of the job.’    ‘Excuse me a moment, but I must confer with the MD’    I popped out to see Chris, the MD. ‘Chris, I’m interviewing a lunatic in a pink suit who is trying to demand that a Ferrari is a precondition of his employment. I tried the ‘misunderstanding trick’ but it didn’t faze him.’     ‘Sorry, Phil, but we’ve got to hire him. The VCs insist on it. You’ve got to think of something that doesn’t involve committing to the purchase of a Ferrari. Current funding barely covers the rent for the building.’    ‘OK boss. Leave it to me.’    On return, I slapped O’Halleran’s file on the table with a genial, paternalistic smile. ‘Of course you should have a Ferrari. The only trouble is that it will require a justification document that can be presented to the board. I’m sure you’ll have no problem in preparing this document in the required format.’ The initial look of despair was quickly followed by a bland look of acquiescence. He had, earlier in the interview, argued with great eloquence his skill in preparing the tiresome documents that underpin the essential corporate and government deals that were vital to the success of this new enterprise. The justification of a Ferrari should be a doddle.     After the interview, Chris nervously asked how I’d fared.     ‘I think it is all solved.’    ‘… without promising a Ferrari, I hope.’    ‘Well, I did actually; on condition he justified it in writing.’    Chris issued a stream of invective. The strain of juggling the resources in an underfunded startup was beginning to show.    ‘Don’t worry. In the unlikely event of him coming back with the required document, I’ll give him mine.’    ‘Yours?’ He strode over to the window to stare down at the car park.    He needn’t have worried: I knew that his breed of marketing man could more easily lay an ostrich egg than to prepare a decent justification document. My Ferrari is still there at the back of my garage. Few know of the Ferrari cultivator, a simple inexpensive motorized device designed for the subsistence farmers of southern Italy. It is the very devil to start, but it creates a perfect tilth for the seedbed.

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  • Productivity vs Security [closed]

    - by nerijus
    Really do not know is this right place to ask such a questions. But it is about programming in a different light. So, currently contracting with company witch pretends to be big corporation. Everyone is so important that all small issues like developers are ignored. Give you a sample: company VPN is configured so that if you have VPN then HTTP traffic is banned. Bearing this in mind can you imagine my workflow: Morning. Ok time to get latest source. Ups, no VPN. Let’s connect. Click-click. 3 sec. wait time. Ok getting source. Do I have emails? Ups. VPN is on, can’t check my emails. Need to wait for source to come up. Finally here it is! Ok Click-click VPN is gone. What is in my email. Someone reported a bug. Good, let’s track it down. It is in TFS already. Oh, dam, I need VPN. Click-click. Ok, there is description. Yea, I have seen this issue in stachoverflow.com. Let’s go there. Ups, no internet. Click-click. No internet. What? IPconfig… DHCP server kicked me out. Dam. Renew ip. 1..2..3. Ok internet is back. Google: site: stachoverflow.com 3 min. I have solution. Great I love stackoverflow.com. Don’t want to remember days where there was no stackoveflow.com. Ok. Copy paste this like to studio. Dam, studio is stalled, can’t reach files on TFS. Click-click. VPN is back. Get source out, paste my code. Grand. Let’s see what other comments about an issue in stackoverflow.com tells. Hmm.. There is a link. Click. Dammit! No internet. Click-click. No internet. DHCP kicked me out. Dammit. Now it is even worse: this happens 3-4 times a day. After certain amount of VPN connections open\closed my internet goes down solid. Only way to get internet back is reboot. All my browser tabs/SQL windows/studio will be gone. This happened just now when I am typing this. Back to issue I am solving right now: I am getting frustrated - I do not care about better solution for this issue. Let’s do it somehow and forget. This Click-click barrier between internet and TFS kills me… Sounds familiar? You could say there are VPN settings to change. No! This is company laptop, not allowed to do changes. I am very very lucky to have admin privileges on my machine. Most of developers don’t. So just learned to live with this frustration. It takes away 40-60 minutes daily. Tried to email company support, admins. They are too important ant too busy with something that just ignored my little man’s problem. Politely ignored. Question is: Is this normal in corporate world? (Have been in States, Canada, Germany. Never seen this.)

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  • Why enumerator structs are a really bad idea

    - by Simon Cooper
    If you've ever poked around the .NET class libraries in Reflector, I'm sure you would have noticed that the generic collection classes all have implementations of their IEnumerator as a struct rather than a class. As you will see, this design decision has some rather unfortunate side effects... As is generally known in the .NET world, mutable structs are a Very Bad Idea; and there are several other blogs around explaining this (Eric Lippert's blog post explains the problem quite well). In the BCL, the generic collection enumerators are all mutable structs, as they need to keep track of where they are in the collection. This bit me quite hard when I was coding a wrapper around a LinkedList<int>.Enumerator. It boils down to this code: sealed class EnumeratorWrapper : IEnumerator<int> { private readonly LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } The key line here is the MoveNext method. When I initially coded this, I thought that the call to m_Enumerator.MoveNext() would alter the enumerator state in the m_Enumerator class variable and so the enumeration would proceed in an orderly fashion through the collection. However, when I ran this code it went into an infinite loop - the m_Enumerator.MoveNext() call wasn't actually changing the state in the m_Enumerator variable at all, and my code was looping forever on the first collection element. It was only after disassembling that method that I found out what was going on The MoveNext method above results in the following IL: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000, [1] valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator CS$0$0001) L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: stloc.1 L_0008: ldloca.s CS$0$0001 L_000a: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000f: stloc.0 L_0010: br.s L_0012 L_0012: ldloc.0 L_0013: ret } Here, the important line is 0002 - m_Enumerator is accessed using the ldfld operator, which does the following: Finds the value of a field in the object whose reference is currently on the evaluation stack. So, what the MoveNext method is doing is the following: public bool MoveNext() { LinkedList<int>.Enumerator CS$0$0001 = this.m_Enumerator; bool CS$1$0000 = CS$0$0001.MoveNext(); return CS$1$0000; } The enumerator instance being modified by the call to MoveNext is the one stored in the CS$0$0001 variable on the stack, and not the one in the EnumeratorWrapper class instance. Hence why the state of m_Enumerator wasn't getting updated. Hmm, ok. Well, why is it doing this? If you have a read of Eric Lippert's blog post about this issue, you'll notice he quotes a few sections of the C# spec. In particular, 7.5.4: ...if the field is readonly and the reference occurs outside an instance constructor of the class in which the field is declared, then the result is a value, namely the value of the field I in the object referenced by E. And my m_Enumerator field is readonly! Indeed, if I remove the readonly from the class variable then the problem goes away, and the code works as expected. The IL confirms this: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000) L_0000: nop L_0001: ldarg.0 L_0002: ldflda valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000c: stloc.0 L_000d: br.s L_000f L_000f: ldloc.0 L_0010: ret } Notice on line 0002, instead of the ldfld we had before, we've got a ldflda, which does this: Finds the address of a field in the object whose reference is currently on the evaluation stack. Instead of loading the value, we're loading the address of the m_Enumerator field. So now the call to MoveNext modifies the enumerator stored in the class rather than on the stack, and everything works as expected. Previously, I had thought enumerator structs were an odd but interesting feature of the BCL that I had used in the past to do linked list slices. However, effects like this only underline how dangerous mutable structs are, and I'm at a loss to explain why the enumerators were implemented as structs in the first place. (interestingly, the SortedList<TKey, TValue> enumerator is a struct but is private, which makes it even more odd - the only way it can be accessed is as a boxed IEnumerator!). I would love to hear people's theories as to why the enumerators are implemented in such a fashion. And bonus points if you can explain why LinkedList<int>.Enumerator.Reset is an explicit implementation but Dispose is implicit... Note to self: never ever ever code a mutable struct.

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  • SQL SERVER – Not Possible – Delete From Multiple Table – Update Multiple Table in Single Statement

    - by pinaldave
    There are two questions which I get every single day multiple times. In my gmail, I have created standard canned reply for them. Let us see the questions here. I want to delete from multiple table in a single statement how will I do it? I want to update multiple table in a single statement how will I do it? The answer is – No, You cannot and you should not. SQL Server does not support deleting or updating from two tables in a single update. If you want to delete or update two different tables – you may want to write two different delete or update statements for it. This method has many issues – from the consistency of the data to SQL syntax. Now here is the real reason for this blog post – yesterday I was asked this question again and I replied my canned answer saying it is not possible and it should not be any way implemented that day. In the response to my reply I was pointed out to my own blog post where user suggested that I had previously mentioned this is possible and with demo example. Let us go over my conversation – you may find it interesting. Let us call the user DJ. DJ: Pinal, can we delete multiple table in a single statement or with single delete statement? Pinal: No, you cannot and you should not. DJ: Oh okey, if that is the case, why do you suggest to do that? Pinal: (baffled) I am not suggesting that. I am rather suggesting that it is not possible and it should not be possible. DJ: Hmm… but in that case why did you blog about it earlier? Pinal: (What?) No, I did not. I am pretty confident. DJ: Well, I am confident as well. You did. Pinal: In that case, it is my word against your word. Isn’t it? DJ: I have proof. Do you want to see it that you suggest it is possible? Pinal: Yes, I will be delighted too. (After 10 Minutes) DJ: Here are not one but two of your blog posts which talks about it - SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2 Pinal: Oh! DJ: I know I was correct. Pinal: Well, oh man, I did not mean there what you mean here. DJ: I did not understand can you explain it further. Pinal: Here we go. The example in the other blog is the example of the cascading delete or cascading update. I think you may want to understand the concept of the foreign keys and cascading update/delete. The concept of cascading exists to maintain data integrity. If there primary keys get deleted the update or delete reflects on the foreign key table to maintain the key integrity and data consistency. SQL Server follows ANSI Entry SQL with regard to referential integrity between PrimaryKey and ForeignKey columns which requires the inserting, updating, and deleting of data in related tables to be restricted to values that preserve the integrity. This is all together different concept than deleting multiple values in a single statement. When I hear that someone wants to delete or update multiple table in a single statement what I assume is something very similar to following. DELETE/UPDATE Table 1 (cols) Table 2 (cols) VALUES … which is not valid statement/syntax as well it is not ASNI standards as well. I guess, after this discussion with DJ, I realize I need to do a blog post so I can add the link to this blog post in my canned answer. Well, it was a fun conversation with DJ and I hope it the message is very clear now. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Joins, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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