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  • Why do condition variables sometimes erroneously wake up?

    - by aspo
    I've known for eons that the way you use a condition variable is lock while not task_done wait on condition variable unlock Because sometimes condition variables will spontaneously wake. But I've never understood why that's the case. In the past I've read it's expensive to make a condition variable that doesn't have that behavior, but nothing more than that. So... why do you need to worry about falsely being woken up when waiting on a condition variable?

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  • Manipulating the address of a variable to store a smaller type?

    - by Sidnicious
    This is what I get for pampering myself with high-level programming languages. I have a function which writes a 32-bit value to a buffer, and a uint64_t on the stack. Is the following code a sane way to store it? uint64_t size = 0; // ... getBytes((uint32_t*)&size+0x1); I'm assuming that this would be the canonical, safe style: uint64_t size = 0; // ... uint32_t smallSize; getBytes(&smallSize); size = smallSize;

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  • How do I get Mathematica to thread a 2-variable function over two lists, using functional programmin

    - by Leah Wrenn Berman
    Lets say I have a function f[x_, y_], and two lists l1, l2. I'd like to evaluate f[x,y] where x runs over the list l1 and y runs over the list l2, and I'd like to do it without having to make all pairs of the form {l1[[i]],l2[[j]]}. (Motivation: I'm trying to implement some basic Haskell programs in Mathematica. In particular, I'd like to be able to code the Haskell program isMatroid::[[Int]]->Bool isMatroid b =and[or[sort(union(xs\\[x])[y]'elem'b|y<-ys]|xs<-b,ys<-b, xs<-x] I think I can do the rest of it, if I can figure out the original question, but I'd like the code to be Haskell-like. Any suggestions for implementing Haskell-like code in Mathematica would be appreciated.)

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  • How can I access a JavaScript variable value in JSP?

    - by Pramod
    function modification() { alert(document.getElementById("record").value); var rec=document.getElementById("record").value; <% Connection connect = DriverManager.getConnection("jdbc:odbc:DSN","scott","tiger"); Statement stm=connect.createStatement(); String record=""; // I want value of "rec" here. ResultSet rstmt=stm.executeQuery("select * from "+record); %> }

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  • How can I pass a const array or a variable array to a function in C?

    - by CSharperWithJava
    I have a simple function Bar that uses a set of values from a data set that is passed in in the form of an Array of data structures. The data can come from two sources: a constant initialized array of default values, or a dynamically updated cache. The calling function determines which data is used and should be passed to Bar. Bar doesn't need to edit any of the data and in fact should never do so. How should I declare Bar's data parameter so that I can provide data from either set? union Foo { long _long; int _int; } static const Foo DEFAULTS[8] = {1,10,100,1000,10000,100000,1000000,10000000}; static Foo Cache[8] = {0}; void Bar(Foo* dataSet, int len);//example function prototype Note, this is C, NOT C++ if that makes a difference; Edit Oh, one more thing. When I use the example prototype I get a type qualifier mismatch warning, (because I'm passing a mutable reference to a const array?). What do I have to change for that?

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  • Problems compiliing c++ code using cygwin

    - by user343403
    I am trying to compile some source code in cygwin (in windows 7) and get the following error when I run the make file g++ -DHAVE_CONFIG_H -I. -I.. -I.. -Wall -Wextra -Werror -g -O2 -MT libcommon_a Fcntl.o -MD -MP -MF .deps/libcommon_a-Fcntl.Tpo -c -o libcommon_a-Fcntl.o `test -f 'Fcntl.cpp' || echo './'`Fcntl.cpp Fcntl.cpp: In function int setCloexec(int): Fcntl.cpp:8: error: 'F_GETFD' was not declared in this scope Fcntl.cpp:8: error: 'fcntl' was not declared in this scope Fcntl.cpp:11: error: 'FD_CLOEXEC' was not declared in this scope Fcntl.cpp:12: error: 'F_SETFD' was not declared in this scope make[4]: *** [libcommon_a-Fcntl.o] Error 1 make[4]: Leaving directory `/abyss-1.1.2/Common' make[3]: *** [all-recursive] Error 1 make[3]: Leaving directory `/abyss-1.1.2' make[2]: *** [all] Error 2 make[2]: Leaving directory `/abyss-1.1.2' make[1]: *** [.build-conf] Error 2 make[1]: Leaving directory `/cygdrive/c/Users/Martin/Documents/NetBeansProjects/abyss-1.1.2_1' make: *** [.build-impl] Error 2 The problem file is:- #include "Fcntl.h" #include <fcntl.h> /* Set the FD_CLOEXEC flag of the specified file descriptor. */ int setCloexec(int fd) { int flags = fcntl(fd, F_GETFD, 0); if (flags == -1) return -1; flags |= FD_CLOEXEC; return fcntl(fd, F_SETFD, flags); } I don't understand what is going on, the file fcntl.h is available and the varaiables that it says were not declared in this scope do not give an error when I compile the file on its own Any help would be much appreciated Many Thanks

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  • How do I maximize a function in Mathematica which takes in a variable length list as input?

    - by Mike
    I have a time-series like function which gives an output based on a list of real numbers(i.e. you can run the function on a list of 1,2,3,... real numbers). The issue I'm encountering is how to maximize the function for a given list length(subject to a set of constraints). I could fix the function to a fixed number of real numbers(i.e. f [x_Real, y_Real] instead of f[x_List]) and treat x and y as the first two elements of the list, and call Maximize on the function, but this is not really elegant. I want to be able to easily change the number of elements in the list. What is the best way to optimize a function like I described, which takes a list as an argument, for a fixed list length?

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  • JS: Why isn't this variable available to the other functions?

    - by Marius Jonsson
    Hello there, I've am trying to make a canvas animation: var context; var meter; var pin; function init() { var meter = new Image(); var pin = new Image(); var context = document.getElementById('canvas').getContext('2d'); meter.src = 'background.png'; pin.src = 'needle.png'; context.drawImage(meter,0,0); context.translate(275,297); context.save(); setTimeout(startup,500); } function startup() { var r=2; // set rpm here. var i=r*36-27; var angleInRadians = 3.14159265 * i/180; //converting degree to radian context.rotate(angleInRadians); //rotating by angle context.drawImage(pin,-250,-3); //adjusting pin center at meter center context.restore(); } You can see the script at http://www.kingoslo.com/instruments/ With firebug I get error saying that context is undefined, which I think is strange. Thanks. Kind regards, Marius

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  • How can you pre-define a variable that will contain an anonymous type?

    - by HitLikeAHammer
    In the simplified example below I want to define result before it is assinged. The linq queries below return lists of anonymous types. result will come out of the linq queries as an IEnumerable<'a but I can't define it that way at the top of the method. Is what I am trying to do possible (in .NET 4)? bool large = true; var result = new IEnumerable(); //This is wrong List<int> numbers = new int[]{1,2,3,4,5,6,7,8,9,10}.ToList<int>(); if (large) { result = from n in numbers where n > 5 select new { value = n }; } else { result = from n in numbers where n < 5 select new { value = n }; } foreach (var num in result) { Console.WriteLine(num.value); } EDIT: To be clear I know that I do not need anonymous types in the example above. It is just to illustrate my question with a small, simple example.

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  • How to set a property of a C# 4 dynamic object when you have the name in another variable

    - by Kieran Benton
    I'm looking for a way to modify properties on a dynamic C# 4.0 object with the name of the property known only at runtime. Is there a way to do something like (ExpandoObject is just used as an example, this could be any class that implements IDynamicMetaObjectProvider): string key = "TestKey"; dynamic e = new ExpandoObject(); e[key] = "value"; Which would be equivalent to: dynamic e = new ExpandoObject(); e.TestKey = "value"; Or is the only way forward reflection?

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  • var in C# - Why can't it be used as a member variable?

    - by David Neale
    Why is it not possible to have implicitly-typed variables at a class level within C# for when these variables are immediately assigned? ie: public class TheClass { private var aList = new List<string>(); } Is it just something that hasn't been implemented or is there a conceptual/technical reason for why it hasn't been done?

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  • how to find the max index of a string from variable in c#?

    - by zoya
    suppose i have a string as string[] _strFile; foreach (ListViewItem item in listview1.Items) { string _strRecFileName = item.SubItems[5].Text; _strFile = _strRecFileName.Split('\\'); } in my listview i have a string as \123\abc\hello\.net\*winxp* now i want to get the last value of the string i.e. winxp in this case.. what is the function to do that? can i use getupperbond function to calculate the upper bound of the string and how to use it?

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  • Adding a computed column to an ActiveRecord query

    - by bmwbzz
    Hi, I am running a query using a scope and some conditions. Something like this: conditions[:offset] = (options[:page].to_i - 1) * PAGE_SIZE unless options[:page].blank? conditions[:limit] = options[:limit] ||= PAGE_SIZE scope = Promo.enabled.active results = scope.all conditions I'd like to add a computed column to the query (at the point when I'm now calling scope.all). Something like this: (ACOS(least(1,COS(0.71106459055501)*COS(-1.2915436464758)*COS(RADIANS(addresses.lat))*COS(RADIANS(addresses.lng))+ COS(0.71106459055501)*SIN(-1.2915436464758)*COS(RADIANS(addresses.lat))*SIN(RADIANS(addresses.lng))+ SIN(0.71106459055501)*SIN(RADIANS(addresses.lat))))*3963.19) as accurate_distance Is there a way to do that without just using find_by_sql and rewriting the whole existing query? Thanks!

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  • PHP Beginner: How to pass PHP variable from one PHP code segment to another ?

    - by Misha Moroshko
    I have index.php which uploads a file to server and sets several PHP variables (like $target_folder_and_file_name). index.php also has the following line (it was originally index.html): <script language="JavaScript" src="main.js.php"></script> After index.php returned to the browser, the browsers asks for main.js.php from the server (right?). Can I access somehow $target_folder_and_file_name from the PHP code in main.js.php ?

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  • How to redirect a URL with GET variables in routes.rb without Rails stripping out the variable first?

    - by Michael Hopkins
    I am building a website in Rails to replace an existing website. In routes.rb I am trying to redirect some of the old URLs to their new equivalents (some of the URL slugs are changing so a dynamic solution is not possible.) My routes.rb looks like this: match "/index.php?page=contact-us" => redirect("/contact-us") match "/index.php?page=about-us" => redirect("/about-us") match "/index.php?page=committees" => redirect("/teams") When I visit /index.php?page=contact-us I am not redirected to /contact-us. I have determined this is because Rails is removing the get variables and only trying to match /index.php. For example, If I pass /index.php?page=contact-us into the below routes I will be redirected to /foobar: match "/index.php?page=contact-us" => redirect("/contact-us") match "/index.php?page=about-us" => redirect("/about-us") match "/index.php?page=committees" => redirect("/teams") match "/index.php" => redirect("/foobar") How can I keep the GET variables in the string and redirect the old URLs the way I'd like? Does Rails have an intended mechanism for this?

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  • problem with sql query, variable value not inserting itself.

    - by Kaustubh
    the old query works, the new on doesnt. the android logcat gives me error as: Failure 1: no such column abcname. abcname is the value of a editview that im trying to get from a popup in android. ================OLD QUERY: MapsActivity.myDB.execSQL("INSERT INTO " +MapsActivity.TableName + " (name, user_comment, latitude, longitude) " + " VALUES ('tagName','tagComment','tagLatitude','tagLongitude');"); ================NEW QUERY: MapsActivity.myDB.execSQL("INSERT INTO " +MapsActivity.TableName + " (name, user_comment, latitude, longitude) " + " VALUES ("+tagName +",'tagComment','tagLatitude','tagLongitude');"); what is the problem?

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  • Doubt in Stored Procedure MySql - how to return multiple values for a variable ?

    - by Eternal Learner
    Hi, I have a stored procedure below. I intend this procedure to return the names of all the movies acted by an actor. Create Procedure ActorMovies( In ScreenName varchar(50), OUT Title varchar(50) ) BEGIN Select MovieTitle INTO Title From Movies Natural Join Acts where Acts.ScreenName = 'ScreenName '; End; I make a call like Call ActorMovies(' Jhonny Depp',@movie); Select @move; The result I get is a Null set , which is not correct.I am expecting a set of movies acted by Jhonny Depp to be returned. I am not sure as to why this is happening?

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  • Is it possible to plot a single density over a discrete variable?

    - by mattrepl
    The x-axis is time broken up into time intervals. There is an interval column in the data frame that specifies the time for each row. Plotting a histogram or line using geom_histogram and geom_freqpoly works great, but I'd like to use geom_density to get a filled area. Perhaps there is a better way to achieve this. Right now, if I use geom_density, curves are created for each discrete factor level instead of smoothing over all of them.

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  • Selenium: How to use stored value in a javascript comparison

    - by dstrube
    I've searched around for the answer to this and found lots of much more complicated questions, but none that gave me insight enough to figure this one out. What I'm doing: 1- open a page with a number that will probably be large 2- get the X Path to where that number is and store it to a variable 3- do a javascript to compare the above stored variable to see if it is bigger than 10, if so, set a new varaible to true; else false (because that is the default value) 4- verify the variable in #3 is true Sounds simple enough, no? Where it goes wrong: At step 3, comparing the variable from step #2 to 10 isn't allowed, at least not the way I'm writing it. Why? Details: <tr> <td>open</td> <td>http://www.google.com/search?hl=en&q=selenium+verifyEval</td> <td></td> </tr> <tr> <td>store</td> <td>/html/body/div[5]/div/p/b[3]</td> <td>resultCount</td> </tr> <tr> <td>storeEval</td> <td>var isMoreThan10 = new Boolean(); isMoreThan10 = (resultCount &gt; 10);</td> <td>isMoreThan10</td> </tr> <tr> <td>verifyExpression</td> <td>${isMoreThan10}</td> <td>true</td> </tr> I just thought of one possible workaround: Exapnd the javascript code to get the value there & assign it to a variable there so I'll be more likely to be able to use that variable in the javascript. Not sure exactly how that would be done- anyone wanna help with that? But surely there is be a better way, isn't there? I must be able to assign a value to a variable in Selenium, then in the next line use that variable in a javascript, right?

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  • how to pass structure variables

    - by deep
    Am having a set of structure variable in one form, i want to use that structure variable as a global variables. i need to use those structure variable in through out my whole application, how to use structure as global variable??

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  • What is the naming convention in Python for variable and function names?

    - by Ray Vega
    Coming from a C# background the naming convention for variables and method names are usually either CamelCase or Pascal Case: // C# example string thisIsMyVariable = "a" public void ThisIsMyMethod() In Python, I have seen the above but I have also seen underscores being used: # python example this_is_my_variable = 'a' def this_is_my_function(): Is there a more preferable, definitive coding style for Python?

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  • How Do I Pass The Value (Not The Reference) of a JS Variable to a Function?

    - by ryan
    Here is a simplified version of something I'm trying to run: for (var i = 0; i < results.length; i++) { marker = results[i]; google.maps.event.addListener(marker, 'click', function() { change_selection(i); }); } but I'm finding that every listener uses the value of results.length (the value when the for loop terminates). How can I add listeners such that each uses the value of i at the time I add it, rather than the reference to i?

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