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  • Visual Studio expression containing a term named "by" cannot be evaluated in the watch window

    - by Andrei Pana
    Consider my C++ code below: int _tmain(int argc, _TCHAR* argv[]) { int by = 10; printf("%d\n", by); int bx = 20; printf("%d\n", (by + bx)); return 0; } which works fine. The funny thing is with the "by" variable. If I try to add a watch for a simple expression that contains by, the result will be CXX0030: Error: expression cannot be evaluated. For example, on a breakpoint on return 0, if I add the following watches I get the results mentioned: by : 10 bx : 20 by + 5 : CXX0030: Error: expression cannot be evaluated bx + 5 : 25 by + bx : CXX0030: Error: expression cannot be evaluated (by) + bx : 30 by + (bx) : CXX0030: Error: expression cannot be evaluated bx + (by) : CXX0014: Error: missing operrand This happens on VS2010, VS2008 on multiple computers. So, more out of curiosity, what is happening with "by"? Is it some kind of strange operator? Why doesn't bx get the same treatment? (I've tried google on this but it is quite difficult to get some relevant hits with terms like "by")

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  • Typecasting EnityObject

    - by AJ
    Hello, I'm new to C# and am stuck on the following. I have a Silverlight web service that uses LINQ to query a ADO.NET entity object. e.g.: [OperationContract] public List<Customer> GetData() { using (TestEntities ctx = new TestEntities()) { var data = from rec in ctx.Customer select rec; return data.ToList(); } } This works fine, but what I want to do is to make this more abstract. The first step would be to return a List<EntityObject> but this gives a compiler error, e.g.: [OperationContract] public List<EntityObject> GetData() { using (TestEntities ctx = new TestEntities()) { var data = from rec in ctx.Customer select rec; return data.ToList(); } } The error is: Error 1 Cannot implicitly convert type 'System.Collections.Generic.List<SilverlightTest.Web.Customer>' to 'System.Collections.Generic.IEnumerable<System.Data.Objects.DataClasses.EntityObject>'. An explicit conversion exists (are you missing a cast?) What am i doing wrong? Thanks, AJ

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  • how to get cartesian products between database and local sequences in linq?

    - by JD
    I saw this similar question here but can't figure out how to use Contains in Cartesian product desired result situation: http://stackoverflow.com/questions/1712105/linq-to-sql-exception-local-sequence-cannot-be-used-in-linq-to-sql-implementatio Let's say I have following: var a = new [] { 1, 4, 7 }; var b = new [] { 2, 5, 8 }; var test = from i in a from j in b select new { A = i, B = j, AB = string.Format("{0:00}a{1:00}b", i, j), }; foreach (var t in test) Console.Write("{0}, ", t.AB); This works great and I get a dump like so (note, I want the cartesian product): 01a02b, 01a05b, 01a08b, 04a02b, 04a05b, 04a08b, 07a02b, 07a05b, 07a08b, Now what I really want is to take this and cartesian product it again against an ID from a database table I have. But, as soon as I add in one more from clause that instead of referencing objects, references SQL table, I get an error. So, altering above to something like so where db is defined as a new DataContext (i.e., class deriving from System.Data.Linq.DataContext): var a = new [] { 1, 4, 7 }; var b = new [] { 2, 5, 8 }; var test = from symbol in db.Symbols from i in a from j in b select new { A = i, B = j, AB = string.Format("{0}{1:00}a{2:00}b", symbol.ID, i, j), }; foreach (var t in test) Console.Write("{0}, ", t.AB); The error I get is following: Local sequence cannot be used in LINQ to SQL implementations of query operators except the Contains operator Its related to not using Contains apparently but I'm unsure how Contains would be used when I don't really want to constrict the results - I want the Cartesian product for my situation. Any ideas of how to use Contains above and still yield the Cartesian product when joining database and local sequences?

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  • (C#) Get index of current foreach iteration

    - by Graphain
    Hi, Is there some rare language construct I haven't encountered (like the few I've learned recently, some on Stack Overflow) in C# to get a value representing the current iteration of a foreach loop? For instance, I currently do something like this depending on the circumstances: int i=0; foreach (Object o in collection) { ... i++; } Answers: @bryansh: I am setting the class of an element in a view page based on the position in the list. I guess I could add a method that gets the CSSClass for the Objects I am iterating through but that almost feels like a violation of the interface of that class. @Brad Wilson: I really like that - I've often thought about something like that when using the ternary operator but never really given it enough thought. As a bit of food for thought it would be nice if you could do something similar to somehow add (generically to all IEnumerable objects) a handle on the enumerator to increment the value that an extension method returns i.e. inject a method into the IEnumerable interface that returns an iterationindex. Of course this would be blatant hacks and witchcraft... Cool though... @crucible: Awesome I totally forgot to check the LINQ methods. Hmm appears to be a terrible library implementation though. I don't see why people are downvoting you though. You'd expect the method to either use some sort of HashTable of indices or even another SQL call, not an O(N) iteration... (@Jonathan Holland yes you are right, expecting SQL was wrong) @Joseph Daigle: The difficulty is that I assume the foreach casting/retrieval is optimised more than my own code would be. @Jonathan Holland: Ah, cheers for explaining how it works and ha at firing someone for using it.

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  • How can I get browser to prompt to save password?

    - by Eric
    Hey, I'm working on a web app that has a login dialog that works like this: User clicks "login" Login form HTML is loaded with AJAX and displayed in DIV on page User enters user/pass in fields and clicks submit. It's NOT a <form> -- user/pass are submitted via AJAX If user/pass are okay, page reloads with user logged in. If user/pass are bad, page does NOT reload but error message appears in DIV and user gets to try again. Here's the problem: the browser never offers the usual "Save this password? Yes / Never / Not Now" prompt that it does for other sites. I tried wrapping the <div> in <form> tags with "autocomplete='on'" but that made no difference. Is it possible to get the browser to offer to store the password without a major rework of my login flow? thanks Eric p.s. to add to my question, I'm definitely working with browers that store passwords, and I've never clicked "never for this site" ...this is a technical issue with the browser not detecting that it's a login form, not operator error :-)

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  • When does it makes sense to use a map?

    - by kiwicptn
    I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have five categories (see below). Assuming more exist, what are they? Please limit each answer to one unique category, put up an example, and vote up the fascinating ones. Property values (like a bean) age -> 30 sex -> male loc -> calgary Histograms peter -> 1 john -> 7 paul -> 5 Presence, with O(1) performance peter -> 1 john -> 1 paul -> 1 Functions peter -> treatPeter() john -> dealWithJohn() paul -> managePaul() Conversion peter -> pierre john -> jean paul -> paul

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  • How to force c# binary int division to return a double?

    - by Wayne
    How to force double x = 3 / 2; to return 1.5 in x without the D suffix or casting? Is there any kind of operator overload that can be done? Or some compiler option? Amazingly, it's not so simple to add the casting or suffix for the following reason: Business users need to write and debug their own formulas. Presently C# is getting used like a DSL (domain specific language) in that these users aren't computer science engineers. So all they know is how to edit and create a few types of classes to hold their "business rules" which are generally just math formulas. But they always assume that double x = 3 / 2; will return x = 1.5 however in C# that returns 1. A. they always forget this, waste time debugging, call me for support and we fix it. B. they think it's very ugly and hurts the readability of their business rules. As you know, DSL's need to be more like natural language. Yes. We are planning to move to Boo and build a DSL based on it but that's down the road. Is there a simple solution to make double x = 3 / 2; return 1.5 by something external to the class so it's invisible to the users? Thanks! Wayne

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  • How to force c# binary int division to return a double?

    - by Wayne
    How to force double x = 3 / 2; to return 1.5 in x without the D suffix or casting? Is there any kind of operator overload that can be done? Or some compiler option? Amazingly, it's not so simple to add the casting or suffix for the following reason: Business users need to write and debug their own formulas. Presently C# is getting used like a DSL (domain specific language) in that these users aren't computer science engineers. So all they know is how to edit and create a few types of classes to hold their "business rules" which are generally just math formulas. But they always assume that double x = 3 / 2; will return x = 1.5 however in C# that returns 1. A. they always forget this, waste time debugging, call me for support and we fix it. B. they think it's very ugly and hurts the readability of their business rules. As you know, DSL's need to be more like natural language. Yes. We are planning to move to Boo and build a DSL based on it but that's down the road. Is there a simple solution to make double x = 3 / 2; return 1.5 by something external to the class so it's invisible to the users? Thanks! Wayne

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  • Singleton with inheritance, Derived class is not able to get instantiated in parent?

    - by yesraaj
    Below code instantiates a derived singleton object based on environment variable. The compiler errors saying error C2512: 'Dotted' : no appropriate default constructor. I don't understand what the compiler is complaining about. #include <stdlib.h> #include <iostream> #include <string> using namespace std; class Dotted; class Singleton{ public: static Singleton instant(){ if (!instance_) { char * style = getenv("STYLE"); if (!style){ if (strcmp(style,"dotted")==0) { instance_ = new Dotted(); return *instance_; } } else{ instance_ = new Singleton(); return *instance_; } } return *instance_; } void print(){cout<<"Singleton";} ~Singleton(){}; protected: Singleton(){}; private: static Singleton * instance_; Singleton(const Singleton & ); void operator=(const Singleton & ); }; class Dotted:public Singleton{ public: void print(){cout<<"Dotted";} protected: Dotted(); }; Dotted::Dotted():Singleton(){} int main(){ Singleton::instant().print(); cin.get(); }

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  • Converting VS2008 Solution to VS2010 Creates compile errors in ASP.NET 3.5 SP1

    - by Lukasz
    I am converting a large solution from Visual Studio 2008 to Visual Studio 2010. The conversion completes without errors. When I go to build the solution one particular section of the application throws error but it didn't when the solution was 2008. Error 1 Could not load file or assembly 'System.Web.DataVisualization, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified. C:\MyProject\Results\Result.ascx 3 And C:\CMyProject\Results\Result.ascx(3): Build (web): Could not load file or assembly 'System.Web.DataVisualization, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified. The dll is in the bin and it is not in the GAC. The .refresh file is pointing to the correct location. And all sections in the Web.Config are there, if you need to see them let me know. I have gone over the fixes I found online and nothing seems to help. I would really appreciate if someone could help me or point me in the right direction? Thank You.

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  • How to parse xml in sql server to process NULL value in DateTime DataType.

    - by Shantanu Gupta
    I have created a sample query in sql server to parse data from xml and to display it right now. Although I will be inserting this data in my table but before that I am facing a simple problem. I want to insert NULL in datetime field ADDED_DATE="NULL" as shown in xml given below. But when I executes this query. It gives me error Conversion failed when converting datetime from character string. What mistake am i doing. Please highlight my mistake. declare @xml varchar(1000) set @xml= ' <ROOT> <TX_MAP FK_GUEST_ID="1" FK_CATEGORY_ID="2" ATTRIBUTE="Test" DESCRIPTION="TestDesc" IS_ACTIVE="1" ADDED_BY="NULL" ADDED_DATE="NULL" MODIFIED_BY="NULL" MODIFIED_DATE="NULL"></TX_MAP> <TX_MAP FK_GUEST_ID="2" FK_CATEGORY_ID="1" ATTRIBUTE="Test2" DESCRIPTION="TestDesc2" IS_ACTIVE="1" ADDED_BY="NULL" ADDED_DATE="NULL" MODIFIED_BY="NULL" MODIFIED_DATE="NULL"></TX_MAP> </ROOT> ' declare @handle int exec sp_xml_preparedocument @handle output, @xml select * from OPENXML(@handle,'/ROOT/TX_MAP',1) with ( FK_GUEST_ID INT ,FK_CATEGORY_ID VARCHAR(10) ,ATTRIBUTE VARCHAR(100) ,[DESCRIPTION] VARCHAR(100) ,IS_ACTIVE VARCHAR(10) ,ADDED_BY VARCHAR(100) ,ADDED_DATE DATETIME NULL ,MODIFIED_BY VARCHAR(100) ,MODIFIED_DATE DATETIME NULL ) I am using Sql Server 2005.

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  • Re-Convert timestamp DATE back to original format (when editing) PHP MySQL

    - by Jess
    Ok so I have managed to get the format of the date presented in HTML (upon display) to how I want (dd/mm/yyy)...However, the user also can change the date via a form. So this is how it's setup as present. Firstly, the conversion from YYYY-MM-DD to DD/MM/YYYY and then display in HTML: $timestamp = strtotime($duedate); echo date('d/m/Y', $timestamp); Now when the user selects to update the due date, the value already stored value is drawn up and presented in my text field (using exactly the same code as above).. All good so far. But when my user runs the update script (clicks submit), the new due date is not being stored, and in my DB its seen as '0000-00-00'. I know I need to convert it back to the correct format that MySQL wants to have it in, in order for it to be saved, but I'm not sure on how to do this. This is what I have so far in my update script (for the due date): $duedate = $_POST['duedate']; $timestamp = strtotime($duedate); date('Y/m/d', $timestamp); $query = "UPDATE films SET filmname= '".$filmname."', duedate= '".$duedate; Can somebody please point me in the right direction to have the new date, when processed, converted back to the accepted format by MySQL. I appreciate any help given! Thanks.

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  • IValueConverter from string

    - by Aleksandar Toplek
    I have an Enum that needs to be shown in ComboBox. I have managed to get enum values to combobox using ItemsSource and I'm trying to localize them. I thought that that could be done using value converter but as my enum values are already strings compiler throws error that IValueConverter can't take string as input. I'm not aware of any other way to convert them to other string value. Is there some other way to do that (not the localization but conversion)? I'm using this marku extension to get enum values [MarkupExtensionReturnType(typeof (IEnumerable))] public class EnumValuesExtension : MarkupExtension { public EnumValuesExtension() {} public EnumValuesExtension(Type enumType) { this.EnumType = enumType; } [ConstructorArgument("enumType")] public Type EnumType { get; set; } public override object ProvideValue(IServiceProvider serviceProvider) { if (this.EnumType == null) throw new ArgumentException("The enum type is not set"); return Enum.GetValues(this.EnumType); } } and in Window.xaml <Converters:UserTypesToStringConverter x:Key="userTypeToStringConverter" /> .... <ComboBox ItemsSource="{Helpers:EnumValuesExtension Data:UserTypes}" Margin="2" Grid.Row="0" Grid.Column="1" SelectedIndex="0" TabIndex="1" IsTabStop="False"> <ComboBox.ItemTemplate> <DataTemplate DataType="{x:Type Data:UserTypes}"> <Label Content="{Binding Converter=userTypeToStringConverter}" /> </DataTemplate> </ComboBox.ItemTemplate> </ComboBox> And here is converter class, it's just a test class, no localization yet. public class UserTypesToStringConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { return (int) ((Data.UserTypes) value) == 0 ? "Fizicka osoba" : "Pravna osoba"; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { return default(Data.UserTypes); } }

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  • Is there a programming toolkit for converting "any file type" to a TIFF image?

    - by Ryan
    Hello, I've written several variations of a program. The purpose of the program is to convert "any file type" to a TIFF image represenation of that file, as if it were being printed using a printer. I'm currently using a third party printer driver that I send files to, and it outputs a TIFF image. This is nice, but it requires me to use Office Interop files, and interact with each individual processing application in order to print the files. I had previously tried a toolkit, called Apose .NET, which did not rely on Office Interop, and did not require any printer driver. It did the conversion all on its own and would create a TIFF image. The problem with Aspose .NET was that it did not support a wide variety of input file types. Most notably, it can't do Visio files. My project calls for the ability to create a TIFF image for virtually "any file type". (excluding exes, music files, and stuff) I know that finding something that handles literally any file type is probably not a very feasible task, so I figure if it can at least handle all the Office file types, Adobe types, and other major standard file types, then I can write a custom extension parsing module that uses those processing applications to do the printing of any file type that can be viewed using those applications. So, does anyone know of a toolkit that can do this? Preferably one that does not rely on Office or a printer driver. It does not have to be free, or open source. Or, if you know of an amazing printer driver that does this, I'm open to that too. Thanks in advance, Ryan

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  • Draw multiple circles in Google Maps

    - by snorpey
    Hi. I want to draw multiple circles on a map, using the Google Maps API anj jQuery. The following code works as long as the line with drawMapCircle() is commented out (The markers are positioned correctly). What's wrong with my code? $.getJSON( "ajax/show.php", function(data) { $.each(data.points, function(i, point) { map.addOverlay(new GMarker(new GLatLng(point.lat, point.lng))); drawMapCircle(point.lat, point.lng, 0.01, '#0066ff', 2, 0.8, '#0cf', 0.1); }); } ); function drawMapCircle(lat, lng, radius, strokeColor, strokeWidth, strokeOpacity, fillColor, fillOpacity) { var d2r = Math.PI / 180; var r2d = 180 / Math.PI; var Clat = radius * 0.014483; // statute miles into degrees latitude conversion var Clng = Clat/Math.cos(lat * d2r); var Cpoints = []; for (var i = 0; i < 33; i++) { var theta = Math.PI * (i / 16); Cy = lat + (Clat * Math.sin(theta)); Cx = lng + (Clng * Math.cos(theta)); var P = new GLatLng(Cy, Cx); Cpoints.push(P); } var polygon = new GPolygon(Cpoints, strokeColor, strokeWidth, strokeOpacity, fillColor, fillOpacity); map.addOverlay(polygon); }

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  • How do I avoid repetition in Java ResourceBundle strings?

    - by Trejkaz
    We had a lot of strings which contained the same sub-string, from sentences about checking the log or how to contact support, to branding-like strings containing the company or product name. The repetition was causing a few issues for ourselves (primarily typos or copy/paste errors) but it also causes issues in that it increases the amount of text our translator has to translate. The solution I came up with went something like this: public class ExpandingResourceBundleControl extends ResourceBundle.Control { public static final ResourceBundle.Control EXPANDING = new ExpandingResourceBundleControl(); private ExpandingResourceBundleControl() { } @Override public ResourceBundle newBundle(String baseName, Locale locale, String format, ClassLoader loader, boolean reload) throws IllegalAccessException, InstantiationException, IOException { ResourceBundle inner = super.newBundle(baseName, locale, format, loader, reload); return inner == null ? null : new ExpandingResourceBundle(inner, loader); } } ExpandingResourceBundle delegates to the real resource bundle but performs conversion of {{this.kind.of.thing}} to look up the key in the resources. Every time you want to get one of these, you have to go: ResourceBundle.getBundle("com/acme/app/Bundle", EXPANDING); And this works fine -- for a while. What eventually happens is that some new code (in our case autogenerated code which was spat out of Matisse) looks up the same resource bundle without specifying the custom control. This appears to be non-reproducible if you write a simple unit test which calls it with and then without, but it occurs when the application is run for real. Somehow the cache inside ResourceBundle ejects the good value and replaces it with the broken one. I am yet to figure out why and Sun's jar files were compiled without debug info so debugging it is a chore. My questions: Is there some way of globally setting the default ResourceBundle.Control that I might not be aware of? That would solve everything rather elegantly. Is there some other way of handling this kind of thing elegantly, perhaps without tampering with the ResourceBundle classes at all?

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  • 'strcpy' error and warning

    - by Leejo
    I'm getting a 'strcpy' error and warning for the following lines: _tcscpy(strCommandLine,_T("MyProgram.exe /param1")); _tcscpy(strApplicationName,_T("MyProgram.exe")); Not sure why I'm getting a 'strcpy' error or warning since I'm not using 'strcpy'. The only lines related to this is: LPCTSTR strApplicationName; LPTSTR strCommandLine; _tcscpy(strCommandLine,_T("MyProgram.exe /param1")); //warning is on this line _tcscpy(strApplicationName,_T("MyProgram.exe")); //error is on this line The output is: 1c:\documents and settings\X.X\my documents\sandbox\sample.cpp(52) : warning C4996: 'strcpy': This function or variable may be unsafe. Consider using strcpy_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. 1 c:\program files\microsoft visual studio 8\vc\include\string.h(74) : see declaration of 'strcpy' 1c:\documents and settings\X.X\my documents\sandbox\sample.cpp(53) : error C2664: 'strcpy' : cannot convert parameter 1 from 'LPCTSTR' to 'char *' 1 Conversion loses qualifiers Any ideas on what this could means? These are my headers: iostream windows.h stdio.h tchar.h winnt.h

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  • How do I pass a const reference in C#?

    - by Maciek
    In C++, passing const references is a common practice - for instance : #include <iostream> using namespace std; class X { public : X() {m_x = 0; } X(const int & x) {m_x = x; } X(const X & other) { *this = other; } X & operator = (const X & other) { m_x = other.m_x; return *this; } void print() { cout << m_x << endl; } private : int m_x; }; void main() { X x1(5); X x2(4); X x3(x2); x2 = x1; x1.print(); x2.print(); x3.print(); } This very simple example illustrates how it's done - pretty much. However I've noticed that in C# this doesn't seem to be the case. Do I have to pass const references in C# ? what do I need the "ref" keyword for? Please note that I know and understand what C# reference and value types are.

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  • Retrive data from two tables in asp.net mvc using ADO.Net Entity Framework

    - by user192972
    Please read my question carefully and reply me. I have two tables as table1 and table2. In table1 i have columns as AddressID(Primary Key),Address1,Address2,City In table2 i have columns as ContactID(Primary Key),AddressID(Foriegn Key),Last Name,First Name. By using join operation i can retrive data from both the tables. I created a Model in my MVC Application.I can see both the tables in enitity editor. In the ViewData folder of my solution explorer i created two class as ContactViewData.cs and SLXRepository.cs In the ContactViewData.cs i have following code public IEnumerable<CONTACT> contacts { get; set; } In the SLXRepository.cs i have following code public IEnumerable<CONTACT> GetContacts() { var contact = ( from c in context.CONTACT join a in context.ADDRESS on c.ADDRESSID equals a.ADDRESSID select new { a.ADDRESS1, a.ADDRESS2, a.CITY, c.FIRSTNAME, c.LASTNAME } ); return contact; } I am getting the error in return type Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Collections.Generic.IEnumerable'. An explicit conversion exists (are you missing a cast?)

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  • Map large integer to a phrase

    - by Alexander Gladysh
    I have a large and "unique" integer (actually a SHA1 hash). I want (for no other reason than to have fun) to find an algorithm to convert that SHA1 hash to a (pseudo-)English phrase. The conversion should be reversible (i.e., knowing the algorithm, one must be able to convert the phrase back to SHA1 hash.) The possible usage of the generated phrase: the human readable version of Git commit ID, like a motto for a given program version (which is built from that commit). (As I said, this is "for fun". I don't claim that this is very practical — or be much more readable than the SHA1 itself.) A better algorithm would produce shorter, more natural-looking, more unique phrases. The phrase need not make sense. I would even settle for a whole paragraph of nonsense. (Though quality — englishness — of a paragraph should probably be better than for a mere phrase.) A variation: it is OK if I will be able to work only with a part of hash. Say, first six digits is OK. Possible approach: In the past I've attempted to build a probability table (of words), and generate phrases as Markov chains, seeding the generator (picking branches from probability tree), according to the bits I read from the SHA. This was not very successful, the resulting phrases were too long and ugly. I'm not sure if this was a bug, or the general flaw in the algorithm, since I had to abandon it early enough. Now I'm thinking about attempting to solve the problem once again. Any advice on how to approach this? Do you think Markov chain approach can work here? Something else?

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  • Good hash function for a 2d index

    - by rlbond
    I have a struct called Point. Point is pretty simple: struct Point { Row row; Column column; // some other code for addition and subtraction of points is there too } Row and Column are basically glorified ints, but I got sick of accidentally transposing the input arguments to functions and gave them each a wrapper class. Right now I use a set of points, but repeated lookups are really slowing things down. I want to switch to an unordered_set. So, I want to have an unordered_set of Points. Typically this set might contain, for example, every point on a 80x24 terminal = 1920 points. I need a good hash function. I just came up with the following: struct PointHash : public std::unary_function<Point, std::size_t> { result_type operator()(const argument_type& val) const { return val.row.value() * 1000 + val.col.value(); } }; However, I'm not sure that this is really a good hash function. I wanted something fast, since I need to do many lookups very quickly. Is there a better hash function I can use, or is this OK?

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  • Are there some cases where Python threads can safely manipulate shared state?

    - by erikg
    Some discussion in another question has encouraged me to to better understand cases where locking is required in multithreaded Python programs. Per this article on threading in Python, I have several solid, testable examples of pitfalls that can occur when multiple threads access shared state. The example race condition provided on this page involves races between threads reading and manipulating a shared variable stored in a dictionary. I think the case for a race here is very obvious, and fortunately is eminently testable. However, I have been unable to evoke a race condition with atomic operations such as list appends or variable increments. This test exhaustively attempts to demonstrate such a race: from threading import Thread, Lock import operator def contains_all_ints(l, n): l.sort() for i in xrange(0, n): if l[i] != i: return False return True def test(ntests): results = [] threads = [] def lockless_append(i): results.append(i) for i in xrange(0, ntests): threads.append(Thread(target=lockless_append, args=(i,))) threads[i].start() for i in xrange(0, ntests): threads[i].join() if len(results) != ntests or not contains_all_ints(results, ntests): return False else: return True for i in range(0,100): if test(100000): print "OK", i else: print "appending to a list without locks *is* unsafe" exit() I have run the test above without failure (100x 100k multithreaded appends). Can anyone get it to fail? Is there another class of object which can be made to misbehave via atomic, incremental, modification by threads? Do these implicitly 'atomic' semantics apply to other operations in Python? Is this directly related to the GIL?

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  • NAMESPACE_SEPARATOR constant

    - by ts
    Hello, Having namespaces in PHP is great. Having '\' as namespace separator is a little bit ... awkward (but if there is someone who thinks that is cool & sexy, I am adding tag "rant" to this post. ;) . So, here goes the question: Are you using in your code NAMESPACE_SEPARATOR constant? As in code below: <?php if (!\defined('NAMESPACE_SEPARATOR') { \define('NAMESPACE_SEPARATOR', '\\'); } // if Pros: consistent with DIRECTORY_SEPARATOR (which all of us are using ;) no mess with escaping (think of '\Foo\Bar' but '\\' . Foo' . '\\' . 'Bar') more readable (IMHO) which gives us in effect an opportunity to write good, namespace-aware autoloaders can resist another change if something scary happens (as with ol'good '::' from PHP 6 alpha) can hide uniquess of '\' as namespace operator in programming language land from strangers ;) Cons: "The reason for DIRECTORY_SEPARATOR is that the value is platform dependent, the namespace separator isn't." (as stated in http://bugs.php.net/bug.php?id=43046) 19 characters instead of 1 ( \ ) or 4 ('\\') There are places where you can't use this (full qualified class names as default class variables) ie: class A { protected $sDefaultReporterClass = '\My\Namespace\DefaultReporter'; } So, what are you thinking ?

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  • linq-to-sql combine child expressions

    - by VictorS
    I need to create and combine several expressions for child entity into one to use it on "Any" operator of a parent. Code now looks like this: Expresion<Child, bool> startDateExpression = t => t.start_date >= startDate; Expression<Child, bool> endDateExpression = t => t.end_date <= endDate; .... ParameterExpression param = startDateExpression.Parameters[0]; Expression<Func<T, bool>> Combined = Expression.Lambda<Func<Child, bool>>( Expression.AndAlso(startDateExpression.Body, startDateExpression.Body), param); //but now I am trying to use combined expression on parent //this line fails just to give an idea on what I am trying to do: //filter type is IQueryable<Parent>; var filter = filter.Where(p =>p.Children.Any(Combined)); How can I do that? Is there better(more elegant way way of doing it?

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  • struts2 trim all string obtained from forms

    - by aelkin
    Hi All, I develop web application using struts2. I want to improve getting string from forms. For this need trim all string and if obtained string is empty then set null to field. For this, I created StringConverter. public class StringConverter extends StrutsTypeConverter { @Override public Object convertFromString(Map context, String[] strings, Class toClass) { if (strings == null || strings.length == 0) { return null; } String result = strings[0]; if (result == null) { return null; } result = result.trim(); if (result.isEmpty()) { return null; } return result; } @Override public String convertToString(Map context, Object object) { if (object != null && object instanceof String) { return object.toString(); } return null; } } Next, I added row to xwork-conversion.properties java.lang.String=com.mypackage.StringConverter Thats all. But I did not get the desired result. convertToString() method is called when jsp build form, but convertFromString() doesn't invoke. What I do wrong? How can I get the same behaviour using another way? Please, not offer solutions such as: remove the value of such form elements using javascript. create util method which will make it using reflection. Then call it for each form bean. Thanks in advance, Alexey.

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