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  • Declaring an integer Range with step != 1 in Ruby

    - by Dan Tao
    Hey guys, I'm completely new to Ruby, so be gentle. Say I want to iterate over the range of even numbers from 2 to 100; how would I do that? Obviously I could do: (2..100).each do |x| if x % 2 == 0 # my code end end But, obviously (again), that would be pretty stupid. I know I could do something like: i = 2 while i <= 100 # my code i += 2 end I believe I could also write my own custom class that provides its own each method (?). I am almost sure that would be overkill, though. I'm interested in two things: Is it possible to do this with some variation of the standard Range syntax (i.e., (x..y).each)? Either way, what would be the most idiomatic "Ruby way" of accomplishing this (using a Range or otherwise)? Like I said, I'm new to the language; so any guidance you can offer on how to do things in a more typical Ruby style would be much appreciated.

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  • Retrieving Oracle Cursor with JDBC

    - by BeginnerAmongBeginners
    I have been experiencing some frustrations trying to make a simple Oracle cursor retrieval procedure work with JDBC. I keep on getting an error of "[Oracle][ODBC][Ora]ORA-06553: PLS-306: wrong number or types of arguments in call to 'GETNAME'", but I cannot figure out what I am doing wrong. Here is my code in Java: CallableStatement stmt = connection.prepareCall("call getName(?)"); stmt.registerOutputParameter(1, OracleTypes.CURSOR); stmt.execute(); stmt.close(); con.close(); Here is my procedure in Oracle: CREATE OR REPLACE PROCEDURE getName(cur out SYS_REFCURSOR) IS BEGIN OPEN cur FOR SELECT name FROM customer; END; Thanks in advance. By the way, I am working with Oracle 10.2.0.

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  • Windows server issue with a product

    - by peter
    Can you tell me the meaning of this statement.I am using windows 2008 server OS Log Problem must be changed so that it elevates privileges for a user executing the Problem. its done by creating a manifest that indicates that Problem needs Administrator privileges.

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  • MySQL::Eliminating redundant elements from a table?

    - by Legend
    I have a table like this: +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | v1 | int(11) | YES | MUL | NULL | | | v2 | int(11) | YES | MUL | NULL | | +-------+---------+------+-----+---------+-------+ There is a tremendous amount of duplication in this table. For instance, elements like the following: +------+------+ | v1 | v2 | +------+------+ | 1 | 2 | | 1 | 3 | | 1 | 4 | | 1 | 5 | | 1 | 6 | | 1 | 7 | | 1 | 8 | | 1 | 9 | | 2 | 1 | | 4 | 1 | | 5 | 1 | | 6 | 1 | | 7 | 1 | | 8 | 1 | | 9 | 1 | +------+------+ The table is large with 1540000 entries. To remove the redundant entries (i.e. to get a table having only (1,9) and no (9,1) entries), I was thinking of doing it with a subquery but is there a better way of doing this?

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  • Python f.write() at beginning of file?

    - by kristus
    I'm doing it like this now, but i want it to write at the beginning of the file instead. f = open('out.txt', 'a') # or 'w'? f.write("string 1") f.write("string 2") f.write("string 3") f.close() so that the contenst of out.txt will be: string 3 string 2 string 1 and not (like this code does): string 1 string 2 string 3

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  • An old flaw in X Window System. How does it work?

    - by Legend
    I was going through an article today when it mentioned the following: "We've found many errors over the years. One of the absolute best was the following in the X Window System: if(getuid() != 0 && geteuid == 0) { ErrorF("Only root"); exit(1); } It allowed any local user to get root access. (The tautological check geteuid == 0 was intended to be geteuid() == 0. In its current form, it compress the address of geteuid to 0; given that the function exists, its address is never 0)." The article explained what was wrong with the code but I would like to know what it means to say that "It allowed any local user to get root access". I am not an expert in C but can someone give me an exact context in which this exploit would work? Specifically, what I mean is, lets say I am the local user, how would I get root access if we assume this code to be present somewhere?

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  • Efficient way to build a MySQL update query in Python

    - by ensnare
    I have a class variable called attributes which lists the instance variables I want to update in a database: attributes = ['id', 'first_name', 'last_name', 'name', 'name_url', 'email', 'password', 'password_salt', 'picture_id'] Each of the class attributes are updated upon instantiation. I would like to loop through each of the attributes and build a MySQL update query in the form of: UPDATE members SET id = self._id, first_name = self._first name ... Thanks.

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  • Use C function in C++ program; "multiply-defined" error

    - by eom
    I am trying to use this code for the Porter stemming algorithm in a C++ program I've already written. I followed the instructions near the end of the file for using the code as a separate module. I created a file, stem.c, that ends after the definition and has extern int stem(char * p, int i, int j) ... It worked fine in Xcode but it does not work for me on Unix with gcc 4.1.1--strange because usually I have no problem moving between the two. I get the error ld: fatal: symbol `stem(char*, int, int)' is multiply-defined: (file /var/tmp//ccrWWlnb.o type=FUNC; file /var/tmp//cc6rUXka.o type=FUNC); ld: fatal: File processing errors. No output written to cluster I've looked online and it seems like there are many things I could have wrong, but I'm not sure what combination of a header file, extern "C", etc. would work.

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  • how to get the parent dir location using python..

    - by zjm1126
    this code is get the templates/blog1/page.html in b.py: path = os.path.join(os.path.dirname(__file__), os.path.join('templates', 'blog1/page.html')) but i want to get the parent dir location: a |---b.py |---templates |--------blog1 |-------page.html and how to get the a location thanks

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  • Is it a good idea for me to learn Python before C or some other Compiler language?

    - by Dream Lane
    Right now I am going through MIT's introduction to Computer Science course via OpenCourseWare. As a part of this course I am learning the Python Language. I've read a lot of things about the benefits of learning C. Before I dig any deeper into Python I wonder if I will be hindered or helped by learning Python first. Do you think that I will develop any bad habits or anything like that from Python?

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  • error when installing rmagic gem on Ubuntu 12.04 for Ruby on Rails

    - by PeaceDefender
    0 down vote favorite I am trying to get my Ruby on Rails application working and installing RMagic gem. But I get an error that says "Can't install RMagick 2.13.1. Can't find the ImageMagick library or one of the dependent libraries." Altough I have ImageMagick installed with its dependences. Terminal log : http://pastebin.com/vcgkbwZR I even tried to installed RMagic from Synaptic, but I get the same error when I run "bundle" command. Through my search, some people had problem with lib dependencies, but I believed I have them all installed. Another solution I found is this ( error installing RMagick from gem ) a little bit old and not sure if it is going to work for 12.04. BUT, I don't know where those configurations should go.

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  • Exceptions confusion

    - by Misiur
    Hi there. I'm trying to build site using OOP in PHP. Everyone is talking about Singleton, hermetization, MVC, and using exceptions. So I've tried to do it like this: Class building whole site: class Core { public $is_core; public $theme; private $db; public $language; private $info; static private $instance; public function __construct($lang = 'eng', $theme = 'default') { if(!self::$instance) { try { $this->db = new sdb(DB_TYPE.':host='.DB_HOST.';dbname='.DB_NAME, DB_USER, DB_PASS); } catch(PDOException $e) { throw new CoreException($e->getMessage()); } try { $this->language = new Language($lang); } catch(LangException $e) { throw new CoreException($e->getMessage()); } try { $this->theme = new Theme($theme); } catch(ThemeException $e) { throw new CoreException($e->getMessage()); } } return self::$instance; } public function getSite($what) { return $this->language->getLang(); } private function __clone() { } } Class managing themes class Theme { private $theme; public function __construct($name = 'default') { if(!is_dir("themes/$name")) { throw new ThemeException("Unable to load theme $name"); } else { $this->theme = $name; } } public function getTheme() { return $this->theme; } public function display($part) { if(!is_file("themes/$this->theme/$part.php")) { throw new ThemeException("Unable to load theme part: themes/$this->theme/$part.php"); } else { return 'So far so good'; } } } And usage: error_reporting(E_ALL); require_once('config.php'); require_once('functions.php'); try { $core = new Core(); } catch(CoreException $e) { echo 'Core Exception: '.$e->getMessage(); } echo $core->theme->getTheme(); echo "<br />"; echo $core->language->getLang(); try { $core->theme->display('footer'); } catch(ThemeException $e) { echo $e->getMessage(); } I don't like those exception handlers - i don't want to catch them like some pokemons... I want to use things simple: $core-theme-display('footer'); And if something is wrong, and debug mode is enabled, then aplication show error. What should i do?

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  • Trying to reinvent the wheel of StackOverflow to have a good learning experience. Need some suggesti

    - by Legend
    I want to learn and am not able to do it unless I have a real "mission" to complete. SO is my favorite and I can't imagine a better experience than actually recreating it but not in ASP. I'd like to use PHP+MySQL+jQuery. So far, I have been a self-taught programmer but I would like to master one paradigm that forces you to adhere to the standards. For instance, recently, jQuery forced me to use some "rules". The plugins were supposed to be written in a particular way and that's it. When I started off, everything seemed like Greek and Latin but when I finished a very small plugin, I felt really happy because it forced me to program in a certain way. I am looking for something like this only in a larger project. I've heard a lot about MVC and all but I am confused about the various frameworks out there. Zend seems awesome but looks heavy at the same time and also requires you to have a lot more control over the web-server whereas CakePHP is a good and a fast framework that needs only little control. Do I use one of these or just write my own MVC? I have the following goals: Goals: Site should be fast - I know this depends on my coding skills but I will learn on my way. The framework itself should not slow me down) Setting up the site should not require you to use command-line - This requirement is ok during development. But some frameworks like Symphony require you to initialize certain things through command-line Should support pluggable modules - For instance, if I want to be able to use the FCK editor, I should be able to organize things in a good way. Should be possible to extend - For instance, SO is mainly a Q&A site but I should be able to logically extend it into an Idea Management System (optional but I'm curious). This goes more into code re-usability I guess. I am comfortable with MySQL so I should be done with database design etc. with some serious effort. As for PHP, I can write code on my own but haven't really used any frameworks that much. jQuery, I started off recently and love it. I would be glad if someone can guide me during these initial steps. Precisely, when designing something like SO, I have the following questions: Do I use a framework? If yes, should it be MVC? If MVC, which one is a good and a scalable one? (I'd love something like jQuery that will not die anytime soon) How do I balance the functionality? The same logic can sometimes be made server centric or client centric. (more Ajax?). Is it a good idea to make a heavy javascript site considering the recent advances on client-side JS processing? Just in case anyone is wondering, I am not interested in commercializing any of this. I need a reason to learn something :)

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  • An array problem in C++

    - by manugupt1
    To access the array indice at the xth position we can use some sort of illustration as shown below #include<iostream> using namespace std; int main(){ float i[20]; for(int j=0;j<=20;j++) i[j]=0; } However the following piece of code does not work #include<iostream> using namespace std; float oldrand[55]; int jrand; void advance_random(){ int j1; float new_random; for(j1=0;j1<=23;j1++){ int temp = j1+30; new_random = (oldrand[j1]) - (oldrand[temp]); if(new_random <0.0) new_random = new_random+1; oldrand[j1] = new_random; } for(j1=24;j1<=54;j1++){ new_random[j1] = oldrand[j1] - oldrand[j1-23]; if(new_random[j1]<0.0) new_random[j1] = new_random + 1; oldrand[j1]=new_random; } } I recieve the following error ga.cpp:20: error: invalid types ‘float[int]’ for array subscript ga.cpp:21: error: invalid types ‘float[int]’ for array subscript ga.cpp:22: error: invalid types ‘float[int]’ for array subscript I am not able to find a mistake in my code please help me

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  • How to provide global functionality in multi-user database app

    - by Mike B
    I have been building a multi-user database application (in C#/WPF 4.0) that manages tasks for all employees of a company. I now need to add some functionality such as sending an email reminder to someone when a critical task is due. How should this be done? Obviously I don’t want every instance of the program to be performing this function (Heh each user would get 10+ emails). Should I add the capability to the application as a "Mode" and then run a copy on the database server in this mode or would it be better to create a new app altogether to perform "Global" type tasks? Is there a better way?

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  • Java queue and multi-dimension array

    - by javaLearner.java
    First of all, this is my code (just started learning java): Queue<String> qe = new LinkedList<String>(); qe.add("b"); qe.add("a"); qe.add("c"); qe.add("d"); qe.add("e"); My question: Is it possible to add element to the queue with two values, like: qe.add("a","1"); // where 1 is integer So, that I know element "a" have value 1. If I want to add a number let say "2" to element a, I will have like a = 3. If this cant be done, what else in java classes that can handle this? I tried to use multi-dimention array, but its kinda hard to do the queue, like pop, push etc. (Maybe I am wrong) How to call specific element in the queue? Like, call element a, to check its value. [Note] Please don't give me links that ask me to read java docs. I was reading, and I still dont get it. The reason why I ask here is because, I know I can find the answer faster and easier.

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  • Books on Debugging Techniques?

    - by zooropa
    Are there any books on debugging techniques? A friend of mine is learning to code and he asked me this question. I told him I don't know of any. Is it that you just have to go through the School of Hard Knocks to learn?

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  • GoTo statements and alternatives in VB.NET

    - by qais
    I've posted a code snippet on another forum asking for help and people pointed out to me that using GoTo statements is very bad programming practice. I'm wondering: why is it bad? What alternatives to GoTo are there to use in VB.NET that would be considered generally more of a better practice? Consider this snippet below where the user has to input their date of birth. If the month/date/year are invalid or unrealistic(using if statements checking the integer inputs size, if there's a better way to do this, I'd appreciate if you could tell me that also :D) How would I be able to loop back to ask the user again? retryday: Console.WriteLine("Please enter the day you were born : ") day = Console.ReadLine If day > 31 Or day < 1 Then Console.WriteLine("Please enter a valid day") GoTo retryday End If

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