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  • Is the a pattern for iterating over lists held by a class (dynamicly typed OO languages)

    - by Roman A. Taycher
    If I have a class that holds one or several lists is it better to allow other classes to fetch those lists(with a getter) or to implement a doXList/eachXList type method for that list that take a function and call that function on each element of the list contained by that object. I wrote a program that did a ton of this and I hated passing around all these lists sometimes with method in class a calling method in class B to return lists contained in class C, B contains a C or multiple C's (note question is about dynamically typed OO languages languages like ruby or smalltalk) ex. (that came up in my program) on a Person class containing scheduling preferences and a scheduler class needing to access them.

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  • Typed metaprogramming languages

    - by Jacques Carette
    I want to do some metaprogramming in a statically typed language, where both my programs and my meta-programs will be typed. I mean this in a strong sense: if my program generator compiles, I want the type system to be strong enough that only type-correct programs can be generated. As far as I know, only metaocaml can do this. (No, neither Template Haskell nor C++ templates fit the bill -- see this paper).

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  • How to get the field name of a java (weak) reference pointing to an object in an other class?

    - by Tom
    Imagine I have the following situation: Test1.java import java.lang.ref.WeakReference; public class Test1 { public WeakReference fieldName; public init() { fieldName = new WeakReference(this); Test2.setWeakRef(fieldName); } } Test2.java import java.lang.ref.WeakReference; public class Test2 { public static setWeakRef(WeakReference weakRef) { //at this point I got weakRef in an other class.. now, how do I get the field name this reference was created with? So that it returns exactly "fieldName", because that's the name I gave it in Test1.java? } } At the location of the comment I received the weak reference created in an other class. How would I retreive the field name that this weak reference was created with, in this case "fieldName"? Thanks in advance.

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  • Using Variables for Class Names in Python?

    - by Sam McAfee
    I want to know how to use variables for objects and function names in Python. In PHP, you can do this: $className = "MyClass"; $newObject = new $className(); How do you do this sort of thing in Python? Or, am I totally not appreciating some fundamental difference with Python, and if so, what is it?

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  • C++: type Length from float

    - by anon
    This is kinda like my earlier question: http://stackoverflow.com/questions/2451175/c-vector3-type-wall Except, now, I want to do this to a builtin rather then a user created type. So I want a type "Length" that behaves just like float -- except I'm going to make it's constructor explicit, so I have to explicitly construct Length objects (rather than have random conversions flying around). Basically, I'm going into the type-a-lot camp.

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  • ASP.Net layered communication

    - by Chris Klepeis
    Hi, We're developing a layered web application. The specs: 3 layers, data layer, business layer, ui layer. Programmed in C# Data Layer uses the entity framework Currently we plan on having the data layer return IEnumerable<T> to the business layer via linq 2 entities, and the business layer will return data to the ui layer. Since the ui layer has no knowledge of the existance of the data layer, how would it handle a result of IEnumerable passed to it from the BLL, where T is defined in the data layer? Are there any GOOD example out there on how to do this. Please note that I'm extremely new to factories / interfaces / abstraction to loosely couple layers. I saw the question here http://stackoverflow.com/questions/917457/passing-data-in-an-ntier-application and it was recommended to have the entity layer shared amongst all layers... however I do not want the other layers to be able to query the database.

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  • C++ and its type system: How to deal with data with multiple types?

    - by sub
    "Introduction" I'm relatively new to C++. I went through all the basic stuff and managed to build 2-3 simple interpreters for my programming languages. The first thing that gave and still gives me a headache: Implementing the type system of my language in C++ Think of that: Ruby, Python, PHP and Co. have a lot of built-in types which obviously are implemented in C. So what I first tried was to make it possible to give a value in my language three possible types: Int, String and Nil. I came up with this: enum ValueType { Int, String, Nil }; class Value { public: ValueType type; int intVal; string stringVal; }; Yeah, wow, I know. It was extremely slow to pass this class around as the string allocator had to be called all the time. Next time I've tried something similar to this: enum ValueType { Int, String, Nil }; extern string stringTable[255]; class Value { public: ValueType type; int index; }; I would store all strings in stringTable and write their position to index. If the type of Value was Int, I just stored the integer in index, it wouldn't make sense at all using an int index to access another int, or? Anyways, the above gave me a headache too. After some time, accessing the string from the table here, referencing it there and copying it over there grew over my head - I lost control. I had to put the interpreter draft down. Now: Okay, so C and C++ are statically typed. How do the main implementations of the languages mentioned above handle the different types in their programs (fixnums, bignums, nums, strings, arrays, resources,...)? What should I do to get maximum speed with many different available types? How do the solutions compare to my simplified versions above?

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  • C#: How to find the default value for a run-time Type?

    - by George Mauer
    So given a static type in your code you can do var defaultMyTypeVal = default(MyType); How would you do the same thing given a variable of Type so you can use it during runtime? In other words how do I implement the following method without a bunch of if statements or using Generics (because I will not know the type I'm passing into the method at compile time)? public object GetDefaultValueForType(Type type) { .... }

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  • Haskell type signature with multiple type somethings (predicates?, for example Eq a =>)

    - by Andrew
    I'm not sure if type predicates is the right term, in fact I've never learned the word for this, so an edit to correct would be helpful - I'm referring to when you give the tipe of function f :: a -> b and you want to say a is a Eq and you say f :: Eq a => a -> b, the name for Eq a => - this is the thing i called a type predicate. My question, though, is how to have multiple of these, so if A is an Eq and B is a Num, I could say either f :: Eq a => a -> b or f :: Num b => a -> b. So, how can I have Eq a => and Num b => at the same time? f :: Eq a => Num b => a -> b, f :: Eq a -> Num b => a -> b, and f :: Eq a, Num b => a -> b all didn't do what I wanted.

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  • Is it OK to use dynamic typing to reduce the amount of variables in scope?

    - by missingno
    Often, when I am initializing something I have to use a temporary variable, for example: file_str = "path/to/file" file_file = open(file) or regexp_parts = ['foo', 'bar'] regexp = new RegExp( regexp_parts.join('|') ) However, I like to reduce the scope my variables to the smallest scope possible so there is less places where they can be (mis-)used. For example, I try to use for(var i ...) in C++ so the loop variable is confined to the loop body. In these initialization cases, if I am using a dynamic language, I am then often tempted to reuse the same variable in order to prevent the initial (and now useless) value from being used latter in the function. file = "path/to/file" file = open(file) regexp = ['...', '...'] regexp = new RegExp( regexp.join('|') ) The idea is that by reducing the number of variables in scope I reduce the chances to misuse them. However this sometimes makes the variable names look a little weird, as in the first example, where "file" refers to a "filename". I think perhaps this would be a non issue if I could use non-nested scopes begin scope1 filename = ... begin scope2 file = open(filename) end scope1 //use file here //can't use filename on accident end scope2 but I can't think of any programming language that supports this. What rules of thumb should I use in this situation? When is it best to reuse the variable? When is it best to create an extra variable? What other ways do we solve this scope problem?

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  • Wireless connected but internet not working, modem is fine because I'm typing over wifi on my android

    - by Sandro Livaja
    I can't connect to the Internet in 11.10. I tried switching my wifi card to another USB slot but nothing changed. Is it possible that the card is able to connect while not being able to receive packages? $ ifconfig eth0 Link encap:Ethernet HWaddr 40:61:86:35:11:b0 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:43 Base address:0x6000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) wlan0 Link encap:Ethernet HWaddr 74:ea:3a:8c:d5:5c inet addr:192.168.2.5 Bcast:192.168.2.255 Mask:255.255.255.0 inet6 addr: fe80::76ea:3aff:fe8c:d55c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:12 errors:0 dropped:0 overruns:0 frame:0 TX packets:102 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1209 (1.2 KB) TX bytes:15329 (15.3 KB)

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  • Should we point to an NSManagedObject entity with weak instead of strong pointer?

    - by Jim Thio
    I think because NSManagedObject is managed by the managedObject context the pointer should be weak. Yet it often goes back to 0 in my cases. for (CategoryNearby * CN in sorted) { //[arrayOfItems addObject:[NSString stringWithFormat:@"%@ - %d",CN.name,[CN.order intValue]]]; NearbyShortcutTVC * tvc=[[NearbyShortcutTVC alloc]init]; tvc.categoryNearby =CN; // tvc.titleString=[NSString stringWithFormat:@"%@",CN.name]; // tvc.displayed=CN.displayed; [arrayOfItemsLocal addObject:tvc]; //CN PO(tvc); PO(tvc.categoryNearby); while (false); } self.arrayOfItems = arrayOfItemsLocal; PO(self.categoriesNearbyInArrayOfItems); [self.tableViewa reloadData]; ... Yet somewhere down the line: tvc.categoryNearby becomes nil. I do not know how or when or where it become nil. How do I debug this? Or should the reference be strong instead? This is the interface of NearbyShortcutTVC by the way @interface NearbyShortcutTVC : BGBaseTableViewCell{ } @property (weak, nonatomic) CategoryNearby * categoryNearby; @end To make sure that we're talking about the same object I print all the memory addresses of the NSArray They're both the exact same object. But somehow the categoryNearby property of the object is magically set to null somewhere. self.categoriesNearbyInArrayOfItems: ( 0x883bfe0, 0x8b6d420, 0x8b6f9f0, 0x8b71de0, 0xb073f90, 0xb061a10, 0xb06a880, 0x8b74940, 0x8b77110, 0x8b794e0, 0x8b7bf40, 0x8b7cef0, 0x8b7f4b0, 0x8b81a30, 0x88622d0, 0x8864e60, 0xb05c9a0 ) self.categoriesNearbyInArrayOfItems: ( 0x883bfe0, 0x8b6d420, 0x8b6f9f0, 0x8b71de0, 0xb073f90, 0xb061a10, 0xb06a880, 0x8b74940, 0x8b77110, 0x8b794e0, 0x8b7bf40, 0x8b7cef0, 0x8b7f4b0, 0x8b81a30, 0x88622d0, 0x8864e60, 0xb05c9a0 )

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  • JVMTI: FollowReferences : how to skip Soft/Weak/Phantom references?

    - by Jayan
    I am writing a small code to detect number of objects left behind after certain actions in our tool. This uses FollowReferences() JVMTI-API. This counts instances reachable by all paths. How can I skip paths that included weak/soft/phantom reference? (IterateThroughHeap counts all objects at the moment, so the number is not fully reliable) Thanks, Jayan

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  • Entity Relationships - Can a weak entity take part in a 'one to many' relationship as the 'one'

    - by jonos
    Hi, With the following entity relationship structure I'm struggling to figure out if the relationship between the LOAN and ITEM is valid? The weak entity of Loan uses a partial key of 'loan_dateLeant' and the primary keys from CUSTOMER and ITEM to form its primary key. However LOAN has a 'one to many' relationship with ITEM as a loan can consist of more than one item. But surely this means that if more than one item is loaned, then the loan record will have two item_id values for part of its primary key?

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  • In windows 7, how do I disable "Ease of Access" pop ups on the logon screen as I am typing my passwo

    - by Silfheed
    Heyas So the question is pretty much in the title. Things to note: 'Use On-Screen Keyboard' is un-checked I have disabled Ease of Access by replacing utilman.exe But my problem now is that when I'm typing my password, It'll stop all together on the 'u' or the 'p' character and I have to click on the ease of access button then move focus back to the password to continue. Yes, one obvious solution is to not use a password that has 'u' or 'p' in it (which I've done), but that's obviously not a completely satisfying answer. Thanks! I feel a tumbleweed badge...

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  • [jquery/javascript] Trigger function when mouse click inside textarea AND type stop typing...

    - by marc
    Welcome, In short, my website use BBcode system, and i want allow users to preview message without posting it. I'm using JQuery library. I need 3 actions. 1) When user click in textarea i want display DIV what will contain preview, i want animate opening. 2) When user typing, i want dynamical load parsed by PHP code to DIV. (i'm still thinking what will be best option... refresh every 2 seconds, or maybe we can detect and refresh after 1 second of inactivity [stop typing]) 3) When user click outside textarea i want close preview div with animation. For example the PHP parser will have patch /api/parser.php and variable by POST called $_POST['message']. Any idea my digital friends ?

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  • Trigger function when mouse click inside textarea AND type stop typing...

    - by marc
    Welcome, In short, my website use BBcode system, and i want allow users to preview message without posting it. I'm using JQuery library. I need 3 actions. 1) When user click in textarea i want display DIV what will contain preview, i want animate opening. 2) When user typing, i want dynamical load parsed by PHP code to DIV. (i'm still thinking what will be best option... refresh every 2 seconds, or maybe we can detect and refresh after 1 second of inactivity [stop typing]) 3) When user click outside textarea i want close preview div with animation. For example the PHP parser will have patch /api/parser.php and variable by POST called $_POST['message']. Any idea my digital friends ?

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  • In windows 7, how do I disable "Ease of Access" pop ups on the logon screen as I am typing my password?

    - by Silfheed
    So the question is pretty much in the title. Things to note: 'Use On-Screen Keyboard' is un-checked I have disabled Ease of Access by replacing utilman.exe But my problem now is that when I'm typing my password, It'll stop all together on the 'u' or the 'p' character and I have to click on the ease of access button then move focus back to the password to continue. Yes, one obvious solution is to not use a password that has 'u' or 'p' in it (which I've done), but that's obviously not a completely satisfying answer. Thanks! I feel a tumbleweed badge...

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  • How to trigger an event in input text after I stop typing/writting?

    - by user1386320
    I want to trigger event just right after I stop typing (not while typing) characters in my input textbox. I've tried with: $('input#username').keypress(function() { var _this = $(this); // copy of this object for further usage setTimeout(function() { $.post('/ajax/fetch', { type: 'username', value: _this.val() }, function(data) { if(!data.success) { // continue working } else { // throw an error } }, 'json'); }, 3000); }); But this example produces a timeout for every typed character and I get about 20 AJAX requests if I type-in 20 characters. On this fiddle I demonstrate the same problem with a simple alert instead of an AJAX. Is there a solution for this or I'm just using a bad approach for this?

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  • why is the address bar black in Google chrome so you cannot see what you're typing ? [closed]

    - by Tim
    The address bar background color in Google Chrome is black. I cannot see what I'm typing. What's going on? This is a problem when you're typing in a URL you've never used before (so there's no matching history). Type in a URL you've never used before. Imagine someone is giving it to you over the phone. Make a typo somewhere. Use the back arrow to go back and correct it. You cannot see where the cursor is. This just started happening yesterday. I'm on WinXP Pro.

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