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  • Can someone exaplain me implicit parameters in Scala?

    - by Oscar Reyes
    And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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  • Can you explain what's going on in this Ruby code?

    - by samoz
    I'm trying to learn Ruby as well as Ruby on Rails right now. I'm following along with Learning Rails, 1st edition, but I'm having a hard time understanding some of the code. I generally do work in C, C++, or Java, so Ruby is a pretty big change for me. I'm currently stumped with the following block of code for a database migrator: def self.up create_table :entries do |t| t.string :name t.timestamps end end Where is the t variable coming from? What does it actually represent? Is it sort of like the 'i' in a for(i=0;i<5;i++) statement? Also, where is the :entries being defined at? (entries is the name of my controller, but how does this function know about that?)

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  • Where to learn about HTTP?

    - by razass
    I am fluent in HTML and PHP and slowly learning JavaScript however I have noticed that there is a huge hole in my knowledge when it comes to understanding how web software communications actually work. I understand the flow of information across the net however I would like to learn about HTTP protocols to better understand how the data is actually sent back and forth through the internet to help me understand things like REST, HTTP Headers, AJAX requests, etc. However, I must be searching the wrong terms because I haven't been able to find a good description of HTTP protocols. Any help is appreciated to point me in the right direction. Thanks!

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  • Refactor or Rewrite

    - by Rick J
    Hmm I have a application in flex (codebase around 20K lines) ... its sort of a social network meets digg kind of thing, I need to add more features to it. This is my first ever flex project. Now im in a dilemma as to whether to refactor or rewrite the application. Im having a lot of trouble understanding the existing code (there is no documentation and the original developer is missing!!). Anyone faced with such a dilemma before? any opinions on what i should do?

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  • nth-child doesn't respond to class

    - by Arne Stephensson
    Is it possible to get the nth-child pseudo-selector to work with a specific class? See this example: http://jsfiddle.net/fZGvH/ I want to have the second DIV.red turn red, but it doesn't apply the color as expected. Not only that, but when you specify this, it changes the 5th DIV to red: div.red:nth-child(6) When you specify this, it changes the 8th DIV to red: div.red:nth-child(9) It seems to be one DIV behind. There are only 8 DIV tags in the example so I don't know why nth-child(9) even works. Testing using Firefox 3.6, but in my actual production code the same problem occurs in Chrome. I'm not understanding something about how this is supposed to work, would appreciate clarification. Also, this will change the 6th DIV to red, but what I actually want is for it to change the second DIV.red to red: div.red:nth-of-type(6) And I don't understand why nth-child() and nth-of-type() respond differently, since there are only eight tags of the same type in the document.

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  • TTPhotoViewController thumbnails rotate but images don't

    - by Koray Balci
    I have PhotoTest1Controller very similiar to the one in Three20 samples. I implemented necessary shouldRotate methods in necessary places in UITabBarController and UINavController derived classes as well as the table that contains PhotoTest1Controller. A funny thing is happening, when in thumbnail mode, the view rotates properly, but when showing a picture it does not respond to rotation. Moreover, If I rotate in thumbnail view and then switch to single image view in that rotation, I find that the image is properly rotated in the background. It only ignores rotation when it is the topmost view! So, my understanding is that shouldRotate events are properly propagated, but for some reason single image view does not rotate when in top view, unlike the example code which is %98 equal to my code...

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  • Question about mysql indexes on low to medium cardinality columns

    - by Kevin J
    I have a general question about the way that database indexing works, particularly in mysql. Let's say I have a table with a million rows with a column "ClientID" that is distributed relatively equally among 30 values. Thus, this column is very low cardinality (30) relative to the primary key (1 million). Now, I understand that you shouldn't create indexes on low cardinality fields. However, in this case, queries are only ever done with one of the 30 clientIDs. Thus, wouldn't creating an index on ClientID be helpful, as the search space is automatically reduced to 1/30th what it normally would be? Or is my understanding of how the index works flawed? Thanks

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  • Using DataTypeAttribute to validate a date

    - by Andy Evans
    I'm having some difficulty understanding how to validate a date (DOB) using MVC2. What I want to do is 1. Is the date entered a valid date and, 2. Is the date at lease 13 years in the past. For example, to validate an email I use the following code: [Required(ErrorMessage = "Email address is required.")] [StringLength(320, ErrorMessage = "Email must be less than 320 characters.")] [Email(ErrorMessage = "This email address is invalid.")] public string email { get; set; } To validate the email I use: public class EmailAttribute : RegularExpressionAttribute { public EmailAttribute() : base("insert long regex expression here") { } } Any assistance would be greatly appreciated, thanks!

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  • How Java Runtime Maps to Targets

    - by zharvey
    According to the Javadocs for Runtime here: Every Java application has a single instance of class Runtime that allows the application to interface with the environment in which the application is running. The current runtime can be obtained from the getRuntime method. An application cannot create its own instance of this class. My question is: what's their definition of an application? Is each JAR/WAR/EAR considered a standalone application? What about a plain ole' Driver.class class with a main() method? What about JEE containers that house EARs and EJBs? I guess I'm trying to understand how many Runtime instances could be up and running inside a complex (JEE) system. And understanding that requires me to understand what specific "things" constitute an "application" in Java terminology. Thanks in advance!

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  • What is recursion? -- In plain english.

    - by Christopher Altman
    I hear this word everyday, but cannot give a meaningful, concise, or plain-english answer to what it is. Recursion is defined by the bastian of knowledge as: Recursion in computer science is a method where the solution to a problem depends on solutions to smaller instances of the same problem.1 The approach can be applied to many types of problems, and is one of the central ideas of computer science.[2] Source Is recursion simply something that repeats itself to get a solution? I am looking for a "Recursion for Dummies" definition, and maybe simple examples. My goal is to be able to understand and explain recursion in my own words. I do not like simply thinking I know the meaning of something because I hear it referenced daily, but have not paused to form my own understanding.

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  • Considering getting into reverse engineering/disassembly

    - by Zombies
    Assuming a decent understanding of assembly on common CPU architectures (eg: x86), how can one explore a potential path (career, fun and profit, etc) into the field of reverse engineering? There is so little educational guides out there so it is difficult to understand what potential uses this has today (eg: is searching for buffer overflow exploits still common, or do stack monitoring programs make this obselete?). I am not looking for any step by step program, just some relevant information such as tips on how to efficiently find a specific area of a program. Basic things in the trade. As well as what it is currently being used for today. So to recap, what current uses does reverse engineering yield today? And how can one find some basic information on how to learn the trade (again it doesn't have to be step-by-step, just anything which can through a clue would be helpful).

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  • Arrays & Pointers

    - by Thomas
    Hi, Looking for some help with arrays and pointers and explanation of what I am trying to do. I want to create a new array on the heap of type Foo* so that I may later assign objects that have been created else where to this array. I am having troubles understanding what I am creating exactly when I do something like the following. Foo *(*f) = new Foo*[10]; Also once I have created my array how do I access each element for example. (f + 9)->fooMember(); ?????? Thanks in advance.

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  • How can I teach a know-it-all beginner programmer?

    - by Liran Orevi
    I need to teach a teenage beginner programmer (private tutoring style). The problem is that despite their poor knowledge and skills, they are sure of their abilities, to the point where I find it hard to teach them "better ways". What's the best way to tackle this? Just to be clear what I'm talking about: Constantly changing between tools/IDEs/libraries when it's tough. Blind certainty that really bad designs are really very good. Copying and pasting from the Internet, without understanding the code, and "marking" it as a project.

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  • Retain, alloc, properties ... Topic to make your Obj-c life easier !

    - by gotye
    Hey everyone, The more I code, the more I get lost ... so I decided to create a topic entirely dedicated to the memory management for me (and others) not to waste hours understanding obj-c basics ... I'll update it as new questions are asked ! Okay below is some examples : // myArray is property (retain) myArray = otherArray; //myArray isn't a property myArray = otherArray; //myArray is a property (retain) myArray = [[NSArray alloc] init]; //myArray isn't a property myArray = [[NSArray alloc] init]; Could you explain to me what happens in every cases ? And especially the number 3 ;) Thanks for the time. Gotye.

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  • car and cdr in Scheme are driving me crazy ...

    - by kristian Roger
    Hi Im facing a problem with the car and cdr functions for example: first I defined a list called it x (define x (a (bc) d ( (ef) g ) )) so x now is equal to (a (bc) d ( (ef) g ) ) now for example I need to get the g from this list using only car and cdr (!! noshortcuts as caddr cddr !!) the correct answer is: (car(cdr(car(cdr(cdr(cdr x)))))) BUT how ? :-( I work according to the rules (the car gives the head of list and cdr gives the tail) and instead of getting the answer above I keep reaching wrong answers. Can any one help me in understanding this ... give me step or a way to solve it step by step Thanks in advance. I'm really sick of Scheme.

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  • Quick example of multi-column results with jQueryUI's new Autocomplete?

    - by Lance May
    I just found out that the jQueryUI now has it's own built-in auto-complete combo box. Great news! Unfortunately, the next thing I found is that making it multi-column doesn't seem nearly that simple (at least via documentation). There is a post here where someone mentions that they've done it (and even gives code), but I'm having trouble understanding what some of their code is doing. I'm just curious if anyone has ran across this before and could post a quick and easy sample of making a multi-column result set. Thanks much in advance.

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  • Android 2.1: Muliple Handlers in a Single Activity

    - by Soumya Simanta
    Hi, I've more than one Handlers in an Activity. I create all the handlers in the onCreate() of the main activity. My understanding is the handlerMessage() method of each handler will never be called at the same time because all messages are put in the same queue (the Activity thread MessageQueue). Therefore, they will be executed in the order in which are put into the Queue. They will also be executed in the main activity thread. Is this correct ? public void onCreate() { this.handler1 = new Handler() { @Override public void handleMessage(Message msg) { //operation 1 : some operation with instanceVariable1 super.handleMessage(msg); } }; this.handler2 = new Handler() { @Override public void handleMessage(Message msg) { //Operation 2: some operation with instanceVariable1 super.handleMessage(msg); } }; this.handler3 = new Handler() { @Override public void handleMessage(Message msg) { //Operation 3: some operation with instanceVariable1 super.handleMessage(msg); } }; }

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  • Modular enterprise architecture using MVC and Orchard CMS

    - by MrJD
    I'm making a large scale MVC application using Orchard. And I'm going to be separating my logic into modules. I'm also trying to heavily decouple the application for maximum extensibility and testability. I have a rudimentary understanding of IoC, Repository Pattern, Unit of Work pattern and Service Layer pattern. I've made myself a diagram. I'm wondering if it is correct and if there is anything I have missed regarding an extensible application. Note that each module is a separate project.

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  • php mysql flex unicode

    - by JonoB
    I have a problem with saving the £ symbol to a mysql database. I am running a flex front end, with a php + mysql backend When I save a record from flex, the string gets sent to the server as "This amount is £10" php views the string as above, and when it gets saved into the DB, it gets saved as "This amount is £10". My understanding is that this is correct based on MySQL or PHP is appending a  whenever the £ is used I now retrieve the above record, and it gets sent to flex as "This amount is £10". Flex correctly displays this in a textarea as "This amount is £10" I change another field in the same record in flex, and re-save the transaction. The string now gets sent to the server as "This amount is £10" The record is now saved into the DB as "The amount is £10". Each time the record is re-saved, this effect snowballs. Thanks for any advice you can give.

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  • Does Seaside scale?

    - by Richard Durr
    Seaside is known as "the heretical web framework". One of the points that make it heretical is that it has much shared state. That however is something which, in my current understanding, hinders easy scaling. Ruby on rails on the other hand shares as less state as possible. It has been known to scale pretty well, even if it is dog slow compared to modern smalltalk vms. flickr uses php and has scaled to an extremly big infrastructure... So has anybody some experience in the scaling of Seaside?

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  • Sqlalchemy layout with WSGI application

    - by TheDude
    I'm working on writing a small WSGI application using Bottle and SqlAlchemy and am confused on how the "layout" of my application should be in terms of SqlAlchemy. My confusion is with creating engines and sessions. My understanding is that I should only create one engine with the 'create_engine' method. Should I be creating an engine instance in the global namespace in some sort of singleton pattern and creating sessions based off of it? How have you done this in your projects? Any insight would be appreciated. The examples in the documentation dont seem to make this entirely clear (unless I'm missing something obvious). Any thoughts?

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  • OWL inferencing question

    - by user439170
    I am using the Jena semantic web framework version 2.6.3. I have code that creates a model with owl inferencing and then adds the following triples: [:bnode-3 rdf:type owl:Restriction] [:bnode-3 owl:onProperty :offspringOf] [:bnode-3 owl:someValuesFrom :Person] [:bnode-3 rdfs:subClassOf :Person] bnode-3 is supposed to be a restriction class which, for example, would contain :joe if :bob is a :Person and the following triple were asserted: [:joe :offspringOf :bob]. Then, since the restriction class is a subclass of Person, :joe would also be a person. And, in fact, this works. Whats confusing to me is that after I assert just the 4 triples at the top of this post, the inferencer creates a blank node which is a Person. In other words, the following triple is now in the model: [_:b0 rdf:type :Person] I don't understand why it would do this. Any help in understanding this would be greatly appreciated. Thanks. Kent.

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  • [Single|Double|Or no] Quotes when using grep?

    - by Hamy
    Grep acts differently depending on what kind of quotes I surround the regex with. I can't seem to get a clear understanding of why this is. Here is an example of the problem: hamiltont$ grep -e show\( test.txt variable.show(); variable.show(a); variable.show(abc, 132); variableshow(); hamiltont$ grep -e "show\(" test.txt grep: Unmatched ( or \( hamiltont$ grep -e 'show\(' test.txt grep: Unmatched ( or \( I am just assuming there is some proper way to enclose the regex with single/double quotes. Any help? FWIW, grep --version returns grep (GNU grep) 2.5.1

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  • dangling pointer, reason for value change after free()?

    - by Aman Jain
    In the following code segment, after free(x), why does y becomes 0? As per my understanding, the memory in the heap that was being pointed to by x, and is still being pointed by y, hasn't been allocated to someone else, so how can it change to 0? And moreover, I don't think it is free(x) that changed it to 0. Any comments? #include <stdio.h> int main ( int argc, char *argv[] ) { int *y = NULL; int *x = NULL; x = malloc(4); *x = 5; y = x; printf("[%d]\n", *y); //prints 5 free(x); printf("[%d]\n", *y); //why doesn't print 5?, prints 0 instead return 0; }

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  • How to implement a Google-chrome-like title bar for Java SWT application

    - by MartyC
    I have inherited development of a Java/SWT application running on Windows only. One of the feature requests that I need to scope is a Google-chrome-type title bar in place of the SWT windows title bar. The application's tabs appear at the same level as the window control buttons. My understanding is that I will need to: write a Windows widget capable of rendering the custom look and managing tabs as opposed to menus. expose the Windows widget as a dll for use in Java via JNI write a custom SWT widget to wrap it and expose the tab management interface. I have a lot of experience with Java programming, GUI programming with Swing/AWT, and non-GUI C# programming. Windows GUI programming and SWT are new to me so I'm not sure where to start. The best I have found so far is a 2001 article on writing your own SWT widget. My biggest unknown is the best way to implement a custom Windows application-window.

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