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  • Debugging Post Request with Chrome Dev Tools

    - by benek
    I am trying to use Chrome Dev for debugging the following Angular post request : $http.post("http://picjboss.puma.lan:8880/fluxpousse/api/flow/createOrUpdateHeader", flowHeader) After running the statement with right-click / evaluate, I can see the post in the network panel with a pending state. How can I get the result or "commit" the request and leave easily this "pending" state from the dev console ? I am not yet very familiar with JS callbacks, some code is expected. Thanks. EDIT I have tried to run from the console : $scope.$apply(function(){$http.post("http://picjboss.puma.lan:8880/fluxpousse/api/flow/createOrUpdateHeader", flowHeader).success(function(data){console.log("error "+data)}).error(function(data){console.log("error "+data)})}) It returns : undefined EDIT The post I am trying to solve generate an HTTP 400. Here is the result : Request URL:http://picjboss.puma.lan:8880/fluxpousse/api/flow/createOrUpdateHeader Request Method:POST Status Code:400 Mauvaise Requ?te Request Headersview source Accept:application/json, text/plain, / Accept-Encoding:gzip,deflate,sdch Accept-Language:fr-FR,fr;q=0.8,en-US;q=0.6,en;q=0.4 Connection:keep-alive Content-Length:5354 Content-Type:application/json;charset=UTF-8 Cookie:JSESSIONID=285AF523EA18C0D7F9D581CDB2286C56 Host:picjboss.puma.lan:8880 Origin:http://picjboss.puma.lan:8880 Referer:http://picjboss.puma.lan:8880/fluxpousse/ User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/30.0.1599.101 Safari/537.36 X-Requested-With:XMLHttpRequest Request Payloadview source {refHeader:IDSFP, idEntrepot:619, codeEntreprise:null, codeBanniere:null, codeArticle:7,…} cessionPrice: 78 codeArticle: "7" codeBanniere: null codeDateAppro: null codeDateDelivery: null codeDatePrepa: null codeEntreprise: null codeFournisseur: null codeUtilisateur: null codeUtilisateurLastUpdate: null createDate: null dateAppro: null dateDelivery: null datePrepa: null hasAssortControl: null hasCadenceForce: null idEntrepot: 619 isFreeCost: null labelArticle: "Mayonnaise de DIJON" labelFournisseur: null listDetail: [,…] pcbArticle: 12 pvc: 78 qte: 78 refCommande: "ref" refHeader: "IDSFP" state: "CREATED" stockArticle: 1200 updateDate: null Response Headersview source Connection:close Content-Length:996 Content-Type:text/html;charset=utf-8 Date:Fri, 08 Nov 2013 15:19:30 GMT Server:Apache-Coyote/1.1 X-Powered-By:Servlet 2.5; JBoss-5.0/JBossWeb-2.1

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  • XMLHttpRequst return null on Chrome

    - by BoltBait
    I have the following code that works fine in IE: <HTML> <BODY> <script language="JavaScript"> text=""; req = new XMLHttpRequest(); if (req) { req.onreadystatechange = processStateChange; req.open("GET", "http://www.boltbait.com", true); req.send(); } function processStateChange() { // is the data ready for use? if (req.readyState == 4) { // process my data alert(req.status); alert(req.responseText); } } </script> </BODY> </HTML> In IE, the first alert returns 200, the second returns the web page. However, in Chrome the first alert returns 0 and the second returns the empty string. My intent is to grab a web page into a string for processing. If I'm not doing this right, how should I be doing this? Thanks.

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  • Recursive QuickSort suffering a StackOverflowException -- Need fresh eyes

    - by jon
    I am working on a Recursive QuickSort method implementation in a GenericList Class. I will have a second method that accepts a compareDelegate to compare different types, but for development purposes I'm sorting a GenericList<int I am recieving stackoverflow areas in different places depending on the list size. I've been staring at and tracing through this code for hours and probably just need a fresh pair of (more experienced)eyes. Definitely wanting to learn why it is broken, not just how to fix it. public void QuickSort() { int i, j, lowPos, highPos, pivot; GenericList<T> leftList = new GenericList<T>(); GenericList<T> rightList = new GenericList<T>(); GenericList<T> tempList = new GenericList<T>(); lowPos = 1; highPos = this.Count; if (lowPos < highPos) { pivot = (lowPos + highPos) / 2; for (i = 1; i <= highPos; i++) { if (this[i].CompareTo(this[pivot]) <= 0) leftList.Add(this[i]); else rightList.Add(this[i]); } leftList.QuickSort(); rightList.QuickSort(); for(i=1;i<=leftList.Count;i++) tempList.Add(leftList[i]); for(i=1;i<=rightList.Count;i++) tempList.Add(rightList[i]); this.items = tempList.items; this.count = tempList.count; } }

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  • Getting random record from database with group by

    - by Saif Bechan
    Hello i have a question on picking random entries from a database. I have 4 tables, products, bids and autobids, and users. Products ------- id 20,21,22,23,24(prime_key) price........... etc........... users ------- id(prim_key) name user1,user2,user3 etc bids ------- product_id user_id created autobids -------- user_id product_id Now a multiple users can have an autobid on an product. So for the next bidder I want to select a random user from the autobid table example of the query in language: for each product in the autobid table I want a random user, which is not the last bidder. On product 20 has user1,user2,user3 an autobidding. On product 21 has user1,user2,user3 an autobidding Then I want a resultset that looks for example like this 20 – user2 21 – user3 Just a random user. I tried miximg the GOUP BY (product_id) and making it RAND(), but I just can't get the right values from it. Now I am getting a random user, but all the values that go with it don't match. Can someone please help me construct this query, I am using php and mysql

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  • PostgreSQL: return select count(*) from old_ids;

    - by Alexander Farber
    Hello, please help me with 1 more PL/pgSQL question. I have a PHP-script run as daily cronjob and deleting old records from 1 main table and few further tables referencing its "id" column: create or replace function quincytrack_clean() returns integer as $BODY$ begin create temp table old_ids (id varchar(20)) on commit drop; insert into old_ids select id from quincytrack where age(QDATETIME) > interval '30 days'; delete from hide_id where id in (select id from old_ids); delete from related_mks where id in (select id from old_ids); delete from related_cl where id in (select id from old_ids); delete from related_comment where id in (select id from old_ids); delete from quincytrack where id in (select id from old_ids); return select count(*) from old_ids; end; $BODY$ language plpgsql; And here is how I call it from the PHP script: $sth = $pg->prepare('select quincytrack_clean()'); $sth->execute(); if ($row = $sth->fetch(PDO::FETCH_ASSOC)) printf("removed %u old rows\n", $row['count']); Why do I get the following error? SQLSTATE[42601]: Syntax error: 7 ERROR: syntax error at or near "select" at character 9 QUERY: SELECT select count(*) from old_ids CONTEXT: SQL statement in PL/PgSQL function "quincytrack_clean" near line 23 Thank you! Alex

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  • LINQ-SQL Updating Multiple Rows in a single transaction

    - by RPM1984
    Hi guys, I need help re-factoring this legacy LINQ-SQL code which is generating around 100 update statements. I'll keep playing around with the best solution, but would appreciate some ideas/past experience with this issue. Here's my code: List<Foo> foos; int userId = 123; using (DataClassesDataContext db = new FooDatabase()) { foos = (from f in db.FooBars where f.UserId = userId select f).ToList(); foreach (FooBar fooBar in foos) { fooBar.IsFoo = false; } db.SubmitChanges() } Essentially i want to update the IsFoo field to false for all records that have a particular UserId value. Whats happening is the .ToList() is firing off a query to get all the FooBars for a particular user, then for each Foo object, its executing an UPDATE statement updating the IsFoo property. Can the above code be re-factored to one single UPDATE statement? Ideally, the only SQL i want fired is the below: UPDATE FooBars SET IsFoo = FALSE WHERE UserId = 123 EDIT Ok so looks like it cant be done without using db.ExecuteCommand. Grr...! What i'll probably end up doing is creating another extension method for the DLINQ namespace. Still require some hardcoding (ie writing "WHERE" and "UPDATE"), but at least it hides most of the implementation details away from the actual LINQ query syntax.

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  • How to easily map c++ enums to strings

    - by Roddy
    I have a bunch of enum types in some library header files that I'm using, and I want to have a way of converting enum values to user strings - and vice-versa. RTTI won't do it for me, because the 'user strings' need to be a bit more readable than the enumerations. A brute force solution would be a bunch of functions like this, but I feel that's a bit too C-like. enum MyEnum {VAL1, VAL2,VAL3}; String getStringFromEnum(MyEnum e) { switch e { case VAL1: return "Value 1"; case VAL2: return "Value 2"; case VAL1: return "Value 3"; default: throw Exception("Bad MyEnum"); } } I have a gut feeling that there's an elegant solution using templates, but I can't quite get my head round it yet. UPDATE: Thanks for suggestions - I should have made clear that the enums are defined in a third-party library header, so I don't want to have to change the definition of them. My gut feeling now is to avoid templates and do something like this: char * MyGetValue(int v, char *tmp); // implementation is trivial #define ENUM_MAP(type, strings) char * getStringValue(const type &T) \ { \ return MyGetValue((int)T, strings); \ } ; enum eee {AA,BB,CC}; - exists in library header file ; enum fff {DD,GG,HH}; ENUM_MAP(eee,"AA|BB|CC") ENUM_MAP(fff,"DD|GG|HH") // To use... eee e; fff f; std::cout<< getStringValue(e); std::cout<< getStringValue(f);

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  • How to enforce users to create objects of class derived from mine with "new" only?

    - by sharptooth
    To implement reference counting we use an IUnknown-like interface and a smart pointer template class. The interface has implementation for all the reference-count methods, including Release(): void IUnknownLike::Release() { if( --refCount == 0 ) { delete this; } } The smart pointer template class has a copy constructor and an assignment operator both accepting raw pointers. So users can do the following: class Class : public IUnknownLike { }; void someFunction( CSmartPointer<Class> object ); //whatever function Class object; someFunction( &object ); and the program runs into undefined behavior - the object is created with reference count zero, the smart pointer is constructed and bumps it to one, then the function returns, smart pointer is destroyed, calls Release() which leads to delete of a stack-allocated variable. Users can as well do the following: struct COuter { //whatever else; Class inner;// IUnknownLike descendant }; COuter object; somefunction( &object.Inner ); and again an object not created with new is deleted. Undefined behavior at its best. Is there any way to change the IUnknownLike interface so that the user is forced to use new for creating all objects derived from IUnknownLike - both directly derived and indirectly derived (with classes in between the most derived and the base)?

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  • Are programming languages and methods inefficient? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in assembler form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually truly believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1: Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when address you desire is further translated before reaching actual RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Because you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect addressing, "my" way would be even faster. 2: Variable allocation duplicity: When you run application, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actual instruction for do so, and that actual number in memory. So, there are 2 entries of the same value in RAM. One in form of instruction, second in form of actual bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • Does/Will autofac's ASP.NET integration support PreInit or Init events?

    - by David Rubin
    I see from poking around in the 1.4.4 source that Autofac's ASP.NET integration (via Autofac.Integration.Web) peforms injection of properties on the Page as part of the HttpContext.PreRequestHandlerExecute event handling, but that the page's child controls don't get their properties injected until Page.PreLoad. What this means, though is that the injected properties of child controls are unavailable for use in the OnInit event handler. For example, this works fine: HelloWorld.aspx: <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="HelloWorld.aspx.cs" Inherits="HelloWorld" %> <html> <body> <asp:Label runat="server" id="lblMsg" OnInit="HandleInit"/> </body> </html> HelloWorld.aspx.cs: ... protected void HandleInit() { lblMsg.Text = _msgProvider.GetMessage(); } public IMsgProvider _msgProvider { private get; set; } // <-- Injected But changing the HelloWorld Page to a UserControl (.acsx) and putting the UserControl in another page doesn't work because _msgProvider isn't injected early enough. Is there a way to make Autofac inject properties of child controls earlier? Or is this something that can be addressed in a future build? Thanks!

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  • Chinese records of sqlite databse are in not accessable in iphone app

    - by Mas
    Hi! I'm creating an iphone app. In which I'm reading data from the sqlite db and presenting it in the tableview control. Problem is that the data is in chinese language. Due to unknown reason, when I read/fetch record from the sqlite table, some records are presented and other are missed by objc. Even objc reads some columns of the missing values, But returns the nil results of the some columns. In reality these columns are not empty. I tried many solutions but didn't find any suitable. Same database is working perfectly in the android version of the app. Any one can help here is the code of reading the chinese records from table Quote *q = [[Quote alloc] init]; q.catId = sqlite3_column_int(statement, 0); q.subCatId = sqlite3_column_int(statement, 1); q.quote = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 2)]; and here is the some records which iphone misses ??????·??? ??????,????????! ??????,??????? Thanks

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  • Problem with writing mobilesubstrate plugins for iOS

    - by overboming
    I am trying to hooking message sending for iOS 3.2, I implement my own hook on a working ExampleHook program I find on the web. But my hook apparently caused segmentation fault everytime it hooks and I don't know why. I want to hook to [NSURL initWithString:(NSString *)URLString relativeToURL:(NSURL *)baseURL; and here is my related implementation static id __$GFWInterceptor_NSURL_initWithString2(NSURL<GFWInterceptor> *_NSURL, NSString *URLString, NSURL* baseURL){ NSLog(@"We have intercepted this url: %@",URLString); [_NSURL __HelloNSURL_initWithString:URLString relativeToURL:baseURL]; establish hook Class _$NSURL = objc_getClass("NSURL"); MSHookMessage(_$NSURL, @selector(initWithString:relativeToURL:), (IMP) &__$GFWInterceptor_NSURL_initWithString2, "__HelloNSURL_"); original method declaration - (void)__HelloNSURL_initWithString:(NSString *)URLString relativeToURL:(NSURL *)baseURL; and here is my gdb backtrace Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address: 0x74696e71 0x335625f8 in objc_msgSend () (gdb) bt 0 0x335625f8 in objc_msgSend () 1 0x32c05b1a in CFStringGetLength () 2 0x32c108a8 in _CFStringIsLegalURLString () 3 0x32b1c32a in -[NSURL initWithString:relativeToURL:] () 4 0x000877c0 in __$GFWInterceptor_NSURL_initWithString2 () 5 0x32b1c220 in +[NSURL URLWithString:relativeToURL:] () 6 0x32b1c1f4 in +[NSURL URLWithString:] () 7 0x3061c614 in createUniqueWebDataURL () 8 0x3061c212 in +[WebFrame(WebInternal) _createMainFrameWithSimpleHTMLDocumentWithPage:frameView:withStyle:editable:] () and apparently it hooks, but there is some memory issue there and I can't find anything to blame now

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  • How can I simply change a class variable from another class in ObjectiveC?

    - by Daniel
    I simply want to change a variable of an object from another class. I can compile without a problem, but my variable always is set to 'null'. I used the following code: Object.h: @interface Object : NSObject { //... NSString *color; //... } @property(nonatomic, retain) NSString* color; + (id)Object; - (void)setColor:(NSString*)col; - (NSString*)getColor; @end Object.m: +(id)Object{ return [[[Object alloc] init] autorelease]; } - (void)setColor:(NSString*)col { self.color = col; } - (NSString*)getColor { return self.color; } MyViewController.h #import "Object.h" @interface ClassesTestViewController : UIViewController { Object *myObject; UILabel *label1; } @property UILabel *label1; @property (assign) Object *myObject; @end MyViewController.m: #import "Object.h" @implementation MyViewController @synthesize myObject; - (void)viewDidLoad { [myObject setColor:@"red"]; NSLog(@"Color = %@", [myObject getColor]); [super viewDidLoad]; } The NSLog message is always Color = (null) I tried many different ways to solve this problem, but no success. Any help would be appreciated.

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  • Create new or update existing entity at one go with JPA

    - by Alex R
    A have a JPA entity that has timestamp field and is distinguished by a complex identifier field. What I need is to update timestamp in an entity that has already been stored, otherwise create and store new entity with the current timestamp. As it turns out the task is not as simple as it seems from the first sight. The problem is that in concurrent environment I get nasty "Unique index or primary key violation" exception. Here's my code: // Load existing entity, if any. Entity e = entityManager.find(Entity.class, id); if (e == null) { // Could not find entity with the specified id in the database, so create new one. e = entityManager.merge(new Entity(id)); } // Set current time... e.setTimestamp(new Date()); // ...and finally save entity. entityManager.flush(); Please note that in this example entity identifier is not generated on insert, it is known in advance. When two or more of threads run this block of code in parallel, they may simultaneously get null from entityManager.find(Entity.class, id) method call, so they will attempt to save two or more entities at the same time, with the same identifier resulting in error. I think that there are few solutions to the problem. Sure I could synchronize this code block with a global lock to prevent concurrent access to the database, but would it be the most efficient way? Some databases support very handy MERGE statement that updates existing or creates new row if none exists. But I doubt that OpenJPA (JPA implementation of my choice) supports it. Event if JPA does not support SQL MERGE, I can always fall back to plain old JDBC and do whatever I want with the database. But I don't want to leave comfortable API and mess with hairy JDBC+SQL combination. There is a magic trick to fix it using standard JPA API only, but I don't know it yet. Please help.

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  • Hashtable is that fast

    - by Costa
    Hi s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]. Is the hash function of the java string, I assume the rest of languages is similar or close to this implementation. If we have hash-Table and a list of 50 elements. each element is 7 chars ABCDEF1, ABCDEF2, ABCDEF3..... ABCDEFn If each bucket of hashtable contains 5 strings (I think this function will make it one string per bucket, but let us assume it is 5). If we call col.Contains("ABCDEFn"); // will do 6 comparisons and discover the difference on the 7th. The hash-table will take around 70 operations (multiplication and additions) to get the hashcode and to compare with 5 strings in bucket. and BANG it found. For list it will take around 300 comparisons to find it. for the case that there is only 10 elements, the list will take around 70 operations but the Hashtable will take around 50 operations. and note that hashtable operations are more time consuming (it is multiplications). I conclude that HybirdDictionary in .Net probably is the best choice for that most cases that require Hashtable with unknown size, because it will let me use a list till the list becomes more than 10 elements. still need something like HashSet rather than a Dictionary of keys and values, I wonder why there is no HybirdSet!! So what do u think? Thanks

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  • Windows Phone 8 Panorama SelectionIndex not changing on swiping through items

    - by Balraj Singh
    I have created Panorama control and binded PanoramaItem from ItemSource. Now when i am changing the selected Panoramaitem by swiping over them the Selected index is always set to -1. I dont know what wrong i am doing while implementation. neither selectionchange event is getting fired. Code: <phone:Panorama Grid.Row="1" Visibility="Visible" x:Name="PnrVwMainNews" ItemsSource="{Binding ParnormaItemsData}" ItemContainerStyle="{StaticResource PanoramaContainerItemStyle}"> <phone:Panorama.ItemTemplate> <DataTemplate> <!-- Panorma Items Template --> <Controls:DynamicContentControl Content="{Binding UsrCntrlDynamic}" /> </DataTemplate> </phone:Panorama.ItemTemplate> </phone:Panorama> PanoramaContainerItemStyle <Style x:Key="PanoramaContainerItemStyle" TargetType="phone:PanoramaItem"> <Setter Property="HorizontalContentAlignment" Value="Stretch" /> <Setter Property="VerticalContentAlignment" Value="Stretch" /> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="phone:PanoramaItem"> <Grid Background="{TemplateBinding Background}" Margin="12,0,0,0"> <Grid.RowDefinitions> <RowDefinition Height="auto" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <ContentPresenter Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" Grid.Row="1" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" /> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style>

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  • How do common web frameworks (Django, Rails, Symfony, etc) handle multiple instances of the same plu

    - by Steven Wei
    Do any of the popular web frameworks solve this problem well? Here's an example: suppose you're running one of these web frameworks and you want to install a blog plugin. Except instead of a single blog, you need to run two separate instances of the blog plugin, and you want to keep them segregated. Or say you want to install multiple instances of a user authentication plugin, because you want to segregate your administrative users from your customer user accounts. Or say you want to install multiple instances of a wiki plugin for different parts of your site, or multiple instances of a comments plugin, or whatever else. It seems to me that at the basic level, each instance of plugin would need to be able to configured with a different set of database tables, and would need to be 'installed' at a different URL path. My experience is mostly with Django and Symfony, and I haven't seen a clean solution to this problem in either of them. They both tend to assume that each plugin (or app, in Django's case) is only ever going to be installed once. I'm curious if the Rails folks have figured out a clean solution to this problem, or any other framework authors (in any language). And if you were going to design a solution to this problem, what would it look like?

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  • Help me write my LISP :) LISP environments, Ruby Hashes...

    - by MikeC8
    I'm implementing a rudimentary version of LISP in Ruby just in order to familiarize myself with some concepts. I'm basing my implementation off of Peter Norvig's Lispy (http://norvig.com/lispy.html). There's something I'm missing here though, and I'd appreciate some help... He subclasses Python's dict as follows: class Env(dict): "An environment: a dict of {'var':val} pairs, with an outer Env." def __init__(self, parms=(), args=(), outer=None): self.update(zip(parms,args)) self.outer = outer def find(self, var): "Find the innermost Env where var appears." return self if var in self else self.outer.find(var) He then goes on to explain why he does this rather than just using a dict. However, for some reason, his explanation keeps passing in through my eyes and out through the back of my head. Why not use a dict, and then inside the eval function, when a new "sub-environment" needs to be created, just take the existing dict and update the key/value pairs that need to be updated, and pass that new dict into the next eval? Won't the Python interpreter keep track of the previous "outer" envs? And won't the nature of the recursion ensure that the values are pulled out from "inner" to "outer"? I'm using Ruby, and I tried to implement things this way. Something's not working though, and it might be because of this, or perhaps not. Here's my eval function, env being a regular Hash: def eval(x, env = $global_env) ........ elsif x[0] == "lambda" then ->(*args) { eval(x[2], env.merge(Hash[*x[1].zip(args).flatten(1)])) } ........ end The line that matters of course is the "lambda" one. If there is a difference, what's importantly different between what I'm doing here and what Norvig did with his Env class? If there's no difference, then perhaps someone can enlighten me as to why Norvig uses the Env class. Thanks :)

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  • Encapsulating user input of data for a class (C++)

    - by Dr. Monkey
    For an assignment I've made a simple C++ program that uses a superclass (Student) and two subclasses (CourseStudent and ResearchStudent) to store a list of students and print out their details, with different details shown for the two different types of students (using overriding of the display() method from Student). My question is about how the program collects input from the user of things like the student name, ID number, unit and fee information (for a course student) and research information (for research students): My implementation has the prompting for user input and the collecting of that input handled within the classes themselves. The reasoning behind this was that each class knows what kind of input it needs, so it makes sense to me to have it know how to ask for it (given an ostream through which to ask and an istream to collect the input from). My lecturer says that the prompting and input should all be handled in the main program, which seems to me somewhat messier, and would make it trickier to extend the program to handle different types of students. I am considering, as a compromise, to make a helper class that handles the prompting and collection of user input for each type of Student, which could then be called on by the main program. The advantage of this would be that the student classes don't have as much in them (so they're cleaner), but also they can be bundled with the helper classes if the input functionality is required. This also means more classes of Student could be added without having to make major changes to the main program, as long as helper classes are provided for these new classes. Also the helper class could be swapped for an alternative language version without having to make any changes to the class itself. What are the major advantages and disadvantages of the three different options for user input (fully encapsulated, helper class or in the main program)?

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  • Reversible numerical calculations in Prolog

    - by user8472
    While reading SICP I came across logic programming chapter 4.4. Then I started looking into the Prolog programming language and tried to understand some simple assignments in Prolog. I found that Prolog seems to have troubles with numerical calculations. Here is the computation of a factorial in standard Prolog: f(0, 1). f(A, B) :- A > 0, C is A-1, f(C, D), B is A*D. The issues I find is that I need to introduce two auxiliary variables (C and D), a new syntax (is) and that the problem is non-reversible (i.e., f(5,X) works as expected, but f(X,120) does not). Naively, I expect that at the very least C is A-1, f(C, D) above may be replaced by f(A-1,D), but even that does not work. My question is: Why do I need to do this extra "stuff" in numerical calculations but not in other queries? I do understand (and SICP is quite clear about it) that in general information on "what to do" is insufficient to answer the question of "how to do it". So the declarative knowledge in (at least some) math problems is insufficient to actually solve these problems. But that begs the next question: How does this extra "stuff" in Prolog help me to restrict the formulation to just those problems where "what to do" is sufficient to answer "how to do it"?

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  • OOP, Interface Design and Encapsulation

    - by Mau
    C# project, but it could be applied to any OO languages. 3 interfaces interacting: public interface IPublicData {} public /* internal */ interface IInternalDataProducer { string GetData(); } public interface IPublicWorker { IPublicData DoWork(); IInternalDataProducer GetInternalProducer(); } public class Engine { Engine(IPublicWorker worker) {} IPublicData Run() { DoSomethingWith(worker.GetInternalProducer().GetData()); return worker.DoWork(); } } Clearly Engine is parametric in the actual worker that does the job. A further source of parametrization is how we produce the 'internal data' via IInternalDataProducer. This implementation requires IInternalDataProducer to be public because it's part of the declaration of the public interface IPublicWorker. However, I'd like it to be internal since it's only used by the engine. A solution is make the IPublicWorker produce the internal data itself, but that's not very elegant since there's only a couple of ways of producing it (while there are many more worker implementations), therefore it's nice to delegate to a couple of separate concrete classes. Moreover, the IInternalDataProducer is used in more places inside the engine, so it's good for the engine to pass around the actual object. I'm looking for elegant ideas/patterns. Cheers :-)

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  • CSS style refresh in IE after dynamic removal of style link

    - by rybz
    Hi! I've got a problem with the dynamic style manipulation in IE7 (IE8 is fine). Using javascript I need to add and remove the < link / node with the definition of css file. Adding and removing the node as a child of < head / works fine under Firefox. Unfortunately, after removing it in the IE, although The tag is removed properly, the page style does not refresh. In the example below a simple css (makes background green) is appended and removed. After the removal in FF the background turns default, but in IE stays green. index.html <html> <head> </head> <script language="javascript" type="text/javascript"> var node; function append(){ var headID = document.getElementsByTagName("head")[0]; node = document.createElement('link'); node.type = 'text/css'; node.rel = 'stylesheet'; node.href = "s.css"; node.media = 'screen'; headID.appendChild(node); } function remove(){ var headID = document.getElementsByTagName("head")[0]; headID.removeChild(node); } </script> <body> <div onClick="append();"> add </div> <div onClick="remove();"> remove </div> </body> </html> And the style sheet: s.css body { background-color:#00CC33 } Here is the live example: http://rlab.pl/dynamic-style/ Is there a way to get it working?

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  • Bulletin board - Database optimisation

    - by andrew
    This question is a follow on from this Question The project and problem The project I am currently working on is a bulletin board for a large non-profit organisation. The bulletin board will be used to allow inter-office communication within the organisation. I am building the application and have been having trouble extracting the results that I need from my database because I don't think it is properly normalized and because of limitations in my knowledge of relational database theory and mysql. I would appreciate input into the design of the board in general and in particular, ways that the database structure can be improved to facilitate efficient queries and help me develop this application and future application faster Business Logic The bulletin board will be used in the following way Posting bulletins and responses to bulletins Employees or 'users' in offices around the country will be able to post messages to the bulletin board.Bulletins must be posted to a location and categorised- i'll call these "bulletins". Users will be able to post any number of replies to any one bulletin and users will be able to reply to their own bulletin - i'll call these 'replies'. Rating bulletins and replies Users will be able to either 'like' or 'dislike' a bulletin or a reply and the total number of likes or dislikes will be shown for each bulletin or reply. Viewing the bulletin board and responses Bulletins can be displayed chronologically. Users can sort bulletins chronologically or chronologically by the latest reply to that bulletin(let me know if you need more explanation) When a particular bulletin is selected, replies to that bulletin will be displayed chronologically @PerformanceDBA - edited 10:34 est 28/12/10I have begun implementing the data model. I assume that the 6th data model is the physical model because it contains the associative tables. I am going to post any questions that I have below. I will put up a database dump once I am done. I will then put up a list of all the queries that I need to run on the database and begin writing them. I hope you had a good Christmas. I'm in Canada and there's snow! Implementation of Physical model

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  • How to develop Online Shopping Portal Application using PHP ?

    - by Sarang
    I do not know PHP & I have to develop a Shopping Portal with following Definition : Scenario: Online Shopping Portal XYZ.com wants to create an online shopping portal for managing its registered customers and their shopping. The customers need to register themselves first before they do shopping using the shopping portal. However, everyone, whether registered or not, can view the various products along with the prices listed in the portal. The registered customers, after logging in, are allowed to place order for one or more products from the products listed in the portal. Once the order is placed, the customer gets a reference order number and the order status should be “order in process”. The customers can track their order using the given reference number. The management of XYZ.com should be able to modify the order status of a particular reference order number to “shipped” once the products are shipped to the shipping address entered by the customer at the time of placing the order. The Functionalities required are : Create the interface for the XYZ.com shopping portal using HTML/XHTML and CSS. Implement the client side validations using JavaScript. Create the tables using MySQL. Implement the functionality using the server side scripting language, PHP. Integrate all the above tasks and make the XYZ.com shopping portal functional. How do I develop this application with following proper steps of development ?

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  • Most Elegant Way to write isPrime in java

    - by Anantha Kumaran
    public class Prime { public static boolean isPrime1(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } for (int i = 2; i <= Math.sqrt(n) + 1; i++) { if (n % i == 0) { return false; } } return true; } public static boolean isPrime2(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } for (int i = 3; i <= Math.sqrt(n) + 1; i = i + 2) { if (n % i == 0) { return false; } } return true; } } public class PrimeTest { public PrimeTest() { } @Test public void testIsPrime() throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { Prime prime = new Prime(); TreeMap<Long, String> methodMap = new TreeMap<Long, String>(); for (Method method : Prime.class.getDeclaredMethods()) { long startTime = System.currentTimeMillis(); int primeCount = 0; for (int i = 0; i < 1000000; i++) { if ((Boolean) method.invoke(prime, i)) { primeCount++; } } long endTime = System.currentTimeMillis(); Assert.assertEquals(method.getName() + " failed ", 78498, primeCount); methodMap.put(endTime - startTime, method.getName()); } for (Entry<Long, String> entry : methodMap.entrySet()) { System.out.println(entry.getValue() + " " + entry.getKey() + " Milli seconds "); } } } I am trying to find the fastest way to check whether the given number is prime or not. This is what is finally came up with. Is there any better way than the second implementation(isPrime2).

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