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• How to increase my "advanced" knowledge of PHP further? (quickly)

  - by Kerry

  I have been working with PHP for years and gotten a very good grasp of the language, created many advanced and not-so-advanced systems that are working very well. The problem I'm running into is that I only learn when I find a need for something that I haven't learned before. This causes me to look up solutions and other code that handles the problem, and so I will learn about a new function or structure that I hadn't seen before. It is in this way that I have learned many of my better techniques (such as studying classes put out by Amazon, Google or other major companies). The main problem with this is the concept of not being able to learn something if you don't know it exists. For instance, it took me several months of programming to learn about the empty() function, and I simply would check the string length using strlen() to check for empty values. I'm now getting into building bigger and bigger systems, and I've started to read blogs like highscalability.com and been researching MySQL replication and server data for scaling. I know that structure of your code is very important to make full systems work. After reading a recent blog about reddit's structure, it made me question if there is some standard or "accepted systems" out there. I have looked into frameworks (I've used Kohana, which I regretted, but decided that PHP frameworks were not for me) and I prefer my own library of functions rather than having a framework. My current structure is a mix between WordPress, Kohana and my own knowledge. The ways I can see as being potentially beneficial are: Read blogs Read tutorials Work with someone else Read a book What would be the best way(s) to "get to the next level" the level of being a very good system developer?

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• Mapping a URL to a service inside a class library

  - by johnk82swe

  I'm developing a small content management solution than can be used in any ASP.NET 3.5 website. The website references some dll's and then lets the aspx's inherit my page baseclass. Some configuration in web.config is also needed, but thats it. Now I'm building a standalone Silverlight editor for the CMS. My idea is that it should communicate with the server using web services. But the question is how to make this service available to the editor? I don't want the website developers having to bother with it. If I used a REST API rather than SOAP I could just create an HttpHandler in my class library and let the website developers add a handler to it in web.config with the path "editor" and then the editor could communicate with that handler on mywebsite.com/editor. Is there any way to achieve the same with a asmx or wcf service? The important thing is that the website developers never have to set up any asmx files or anything. They should only have to specify a url and map that url to a service inside my class library. Thanks in advance!

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• Variable wont echo

  - by jonnnnnnnnnie

  I have the following code, where the var $username doesn't echo, when you type in a value. //TODO: SET AUTH TOKEN as random hash, save in session $auth_token = rand(); if (isset($_POST['action']) && $_POST['action'] == 'Login') { $errors = array(); //USED TO BUILD UP ARRAY OF ERRORS WHICH ARE THEN ECHOED $username = $_POST['username']; if ($username = '') { $errors['username'] = 'Username is required'; } echo $username; // var_dump($username) returns string 0 } require_once 'login_form.html.php'; ?> login_form is this: <form method="POST" action=""> <input type="hidden" name="auth_token" value="<?php echo $auth_token ?>"> Username: <input type="text" name="username"> Password: <input type="password" name="password1"> <input type="submit" name="action" value="Login"> </form> The auth token part isn't important, it just when I type in a value in username textbox and press the login button, the username wont echo, var_dump returns string (0) and print_r is just blank.

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• autoreload webpage on new release

  - by user3726562

  I have a website in PHP which is completely ajax-based. There is an index.php, but a part from it, all the other page are never rendered directly into the browser. Instead, all the post and get request are done tfrom javascript through ajax. So basically, if you go to /contact.php you will not see anything. All the pages are rendered inside index.php. So, there are a lot of people that use this page that are not very good in using the web. Asking them to "refresh" the page makes them to wonder what we are talking about. Unfortunately. The biggest issue happens when we do a new release. Especially the javascript code (but not only) can be the old one in a client's webpage as they maybe havent refreshed the page for some week (lol). S I do an svn-update and the new code is on the server. I just refresh my page and see the new features. However, the poor guys that dont really know how to make a refresh, will not see anything. I have added a big button on the page with the text "refresh". Which makes a location.reload. Hopefully this can help a few of them. But my question is: how to "force" the browser to reload itself when a new svn-version has been released? Hopefully in a simple way, without needing some node.js, javascript timer or stuff like that. It is also quite important to not refresh the page when the user is doing something with the page (maybe writing a mail in the UI, and then suddenly the page get refreshed: not so good).

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• ASP.NET MVC3 ValueProvider drops string input to a double property

  - by Daniel Koverman

  I'm attempting to validate the input of a text box which corresponds to a property of type double in my model. If the user inputs "foo" I want to know about it so I can display an error. However, the ValueProvider is dropping the value silently (no errors are added to the ModelState). In a normal submission, I fill in "2" for the text box corresponding to myDouble and submit the form. Inspecting controllerContext.HttpContext.Request.Form shows that myDouble=2, among other correct inputs. bindingContext.ValueProvider.GetValue("myDouble") == 2, as expected. The bindingContext.ModelState.Count == 6 and bindingContext.ModelState["myDouble"].Errors.Count == 0. Everything is good and the model binds as expected. Then I fill in "foo" for the text box corresponding to myDouble and submitted the form. Inspecting controllerContext.HttpContext.Request.Form shows that myDouble=foo, which is what I expected. However, bindingContext.ValueProvider.GetValue("myDouble") == null and bindingContext.ModelState.Count == 5 (The exact number isn't important, but it's one less than before). Looking at the ValueProvider, is as if myDouble was never submitted and the model binding occurs as if it wasn't. This makes it difficult to differentiate between a bad input and no input. Is this the expected behavior of ValueProvider? Is there a way to get ValueProvider to report when conversion fails without implementing a custom ValueProvider? Thanks!

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• Embedded Development Board

  - by ALF3130

  I'm new to the embedded development world and am looking to get my very first board. After some research, I realize that there aren't many choices with FPUs. This is important in my project as I'm going to be doing quite a bit of floating point computations. I found the Mini2440 which seems to run on the ARM920T core. This particular unit is perfect for my needs (decent price, all the right I/O ports, and a touch screen to boot) but it seems that it doesn't have an FPU. I don't know how big of a penalty I'd be paying for FP emulation, so I'm unsure of whether to pull the trigger on this one. That said: Can someone please confirm whether this product (Mini2440) has an FPU or not? My project will do image capture and analysis. Does anyone have any experience with running things like OpenMP on such platforms? Please suggest any other similar boards in the = $200 price range that have an FPU. This world is new to me. Any other advice or things I should be aware of is much appreciated.

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• how to use q.js promises to work with multiple asynchronous operations

  - by kimsia

  Note: This question is also cross-posted in Q.js mailing list over here. i had a situation with multiple asynchronous operations and the answer I accepted pointed out that using Promises using a library such as q.js would be more beneficial. I am convinced to refactor my code to use Promises but because the code is pretty long, i have trimmed the irrelevant portions and exported the crucial parts into a separate repo. The repo is here and the most important file is this. The requirement is that I want pageSizes to be non-empty after traversing all the dragged'n dropped files. The problem is that the FileAPI operations inside getSizeSettingsFromPage function causes getSizeSettingsFromPage to be async. So I cannot place checkWhenReady(); like this. function traverseFiles() { for (var i=0, l=pages.length; i<l; i++) { getSizeSettingsFromPage(pages[i], calculateRatio); } checkWhenReady(); // this always returns 0. } This works, but it is not ideal. I prefer to call checkWhenReady just ONCE after all the pages have undergone this function calculateRatio successfully. function calculateRatio(width, height, filename) { // .... code pageSizes.add(filename, object); checkWhenReady(); // this works but it is not ideal. I prefer to call this method AFTER all the `pages` have undergone calculateRatio // ..... more code... } How do I refactor the code to make use of Promises in Q.js?

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• Best way to store this data?

  - by Malfist

  I have just been assigned to renovate an old website, and I get to move it from some old archaic system to drupal. The only problem is that it's a real-estate system and a lot of data is stored. Currently all the information is stored in a single table, an id represents the house and then everything else is key/value pairs. There are a possible 243 keys per estate, there are 23840 estates in the system. As you can imagine the system is slow and difficult to query. I don't think a table with 243 rows would be a very good idea, and probably worse than the current situation. I've done some investigating and here's what I've found out: Missing data does not indicate a 0 value, data is merged from two, unique sources/formats. Some guessing is involved. I have no control over the source of the data. There are 4 keys that are common to all estates, all values look like something that is commonly searched for and could be indexed There are 10 keys that are in the [90-100)% range 8 of these are information like who's selling it, and it's address. The other two seem to belong with the below range There are 80 keys that are in the [80-90)% range This range seems to mostly just list room types and how many the house has (e.g. bedrooms_possible, bathrooms, family_room_3rd, etc) This range also includes some minor information like school districts, one or two more pieces of data on the address. The 179 keys that are in the [0-80)% range include all sorts of miscellaneous information about the estate My best idea was a hybrid approach, create a table that stores important, common information and keep a smaller key/value table. How would you store this information?

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• Stop SQL returning the same result twice in a JOIN

  - by nbs189

  I have joined together several tables to get data i want but since I am new to SQL i can't figure out how to stop data being returned more than once. her's the SQL statement; SELECT T.url, T.ID, S.status, S.ID, E.action, E.ID, E.timestamp FROM tracks T, status S, events E WHERE S.ID AND T.ID = E.ID ORDER BY E.timestamp DESC The data that is returned is something like this; +----------------------------------------------------------------+ | URL | ID | Status | ID | action | ID | timestamp | +----------------------------------------------------------------+ | T.1 | 4 | hello | 4 | has uploaded a track | 4 | time | | T.2 | 3 | bye | 3 | has some news | 3 | time | | t.1 | 4 | more | 4 | has some news | 4 | time | +----------------------------------------------------------------+ That's a very basic example but does outline what happens. If you look at the third row the URL is repeated when there is a different status. This is what I want to happen; +-------------------------------------------------------+ | URL or Status | ID | action | timestamp | +-------------------------------------------------------+ | T.1 | 4 | has uploaded a track | time | | hello | 3 | has some news | time | | bye | 4 | has some news | time | +-------------------------------------------------------+ Please notice that the the url (in this case the mock one is T.1) is shown when the action is has uploaded a track. This is very important. The action in the events table is inserted on trigger of a status or track insert. If a new track is inserted the action is 'has uploaded a track' and you guess what it is for a status. The ID and timestamp is also inserted into the events table at this point. Note: There are more tables that go into the query, 3 more in fact, but I have left them out for simplicity.

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• Simulate Golf Game Strategy

  - by Mitchel Sellers

  I am working on what at best could be considered a "primitive" golf game, where after a certain bit of randomness is introduced I need to play out a hole of golf. The hole is static and I am not concerned about the UI aspect as I just have to draw a line on a graphic of the hole after the ball has been hit showing where it traveled. I'm looking for input on thoughts of how to manage the "logic" side of the puzzle, below are some of my thoughts on the matter, input, suggestions, or references are greatly appreciated. Map out the hole into an array with a specific amount of precision, noting the type of surface: out of bounds, fairway, rough, green, sand, water, and most important the hole. Map out "regions" and if the ball is contained inside one of these regions setup parameters for "maximum" angle of departure. (For example the first part of the hole the shot must be between certain angles Using the current placement of the ball, and the region contained in #2, define a routine to randomly select the shooting angle, and power then move the ball, adjust the trajectory and move again. I know this isn't the "most elegant" solution, but in reality, we are looking for a quick and dirty solution, as I just have to do this a few times, set it and forget it afterward. From a languages perspective I'll be using ASP.NET and C# to get this done.

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• Mobile site not rendering mobile within iframe

  - by user2788371

  I'm launching a mobile version of an existing corporate web application that currently loads in an iframe for corporate authentication purposes. When accessing the web app's direct link from a mobile device, it displays beautifully. The problem is that when accessing through the iframe, the site doesn't seem to scale correctly and it looks more like I'm accessing the desktop version of the site. Any suggestions on how make the site within the iframe recognize the mobile device's width and adjust appropriately? I've tried setting the viewport within the HTML and CSS of the site being loaded and even then I'm not getting the change I expect on my iPhone. I haven't had the opportunity to test an Android yet but within our company, iOS is the most important. Some of snippets of code I have tried are listed below. I've also tried 480px and device-width (which I believe I can't access because the iframe is a different domain). Unfortunately, modifying the iframe page and settings are not an option. Also, Javascript cannot be used as a solution for other reasons. Within HTML of web app site: <meta name="viewport" content="width=320px, initial-scale=1.0, user-scalable=no" /> Within CSS of web app site: @viewport { width: 320px; } The above CSS does not seem to render even when not used in device specific @media code.

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• MATLAB: What is an appropriate Data Structure for a Matrix with Random Variable Entries?

  - by user568249

  I'm currently working in an area that is related to simulation and trying to design a data structure that can include random variables within matrices. To motivate this let me say I have the following matrix: [a b; c d] I want to find a data structure that will allow for a, b, c, d to either be real numbers or random variables. As an example, let's say that a = 1, b = -1, c = 2 but let d be a normally distributed random variable with mean 0 and SD 1. The data structure that I have in mind will give no value to d. However, I also want to be able to design a function that can take in the structure, simulate an uniform(0,1), obtain a value for d using an inverse CDF and then spit out an actual matrix. I have several ideas to do this (all related to the MATLAB icdf function) but would like to know how more experienced programmers would do this. In this application, it's important that the structure is as "lean" as possible since I will be working with very very large matrices and memory will be an issue.

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• An Array returned by a model association is not an Array?

  - by Warren

  We have a model association that looks something like this: class Example < ActiveRecord::Base has_many :others, :order => 'others.rank' end The rank column is an integer type. The details of these particular models are not really important though as we have found the same problem with other has_many associations between other models. We have also added to the Enumerable module: module Enumerable def method_missing(name) super unless name.to_s[0..7] == 'collect_' method = name.to_s[8..-1] collect{|element| element.send(method)} end end This adds a collect_id method that we can use to get an array of record ids from an array of ActiveRecord objects. So if we use a normal ActiveRecord find :all, we get a nice array which we can then use collect_id on but if we use Example.others.collect_id, we get NoMethodError: undefined method `collect_id' for #<Class:0x2aaaac0060a0> Example.others.class returns "Array" so is it lying or confused? Our solution thus far has been to use it this way: Example.others.to_a.collect_id This works but this seems a bit strange. Why would you have to do that? We are on Ruby 1.8.7 and Rails 2.3.4

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• Replacing text with variables

  - by Steve

  I have to send out letters to certain clients and I have a standard letter that I need to use. I want to replace some of the text inside the body of the message with variables. Here is my maturity_letter models.py class MaturityLetter(models.Model): default = models.BooleanField(default=False, blank=True) body = models.TextField(blank=True) footer = models.TextField(blank=True) Now the body has a value of this: Dear [primary-firstname], AN IMPORTANT REMINDER… You have a [product] that is maturing on [maturity_date] with [financial institution]. etc Now I would like to replace everything in brackets with my template variables. This is what I have in my views.py so far: context = {} if request.POST: start_form = MaturityLetterSetupForm(request.POST) if start_form.is_valid(): agent = request.session['agent'] start_date = start_form.cleaned_data['start_date'] end_date = start_form.cleaned_data['end_date'] investments = Investment.objects.all().filter(maturity_date__range=(start_date, end_date), plan__profile__agent=agent).order_by('maturity_date') inv_form = MaturityLetterInvestments(investments, request.POST) if inv_form.is_valid(): sel_inv = inv_form.cleaned_data['investments'] context['sel_inv'] = sel_inv maturity_letter = MaturityLetter.objects.get(id=1) context['mat_letter'] = maturity_letter context['inv_form'] = inv_form context['agent'] = agent context['show_report'] = True Now if I loop through the sel_inv I get access to sel_inv.maturity_date, etc but I am lost in how to replace the text. On my template, all I have so far is: {% if show_letter %} {{ mat_letter.body }} <br/> {{ mat_letter.footer }} {% endif %} Much appreciated.

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• What are the potential problems with exposing the Facebook API secret?

  - by genehack

  I'm writing a little web utility that posts status updates to Twitter and/or Facebook. That involved creating 'applications' with both those services in order to get API keys and 'secrets'. My question is how protected I really need to keep those secrets -- in order for this to work at all, you seem to need the secret to interact with the authentication part of the service to grant the app access to your account and/or grant it permission to post updates on your behalf. Facebook's documentation says to protect the secret, but at least one other Facebook utility distributes the API key and secret in the source. It's important to note: this isn't your standard Facebook 'application' that runs within the context of Facebook, nor is it a standard "desktop"-style compiled app -- it's a web-based application intended to be run on your own web server. The audience for this is probably small and somewhat more sophisticated than average -- so, one technical alternative would be to require people to obtain their own API key and secret to use the app. That seems like a lot of work, however, and a fairly large barrier to entry to anybody using this. Anybody know or have any insight on what sort of trouble I'm letting myself in for if I put both the secrets and the API keys in the config for my app and check it into Github for all the world to see?

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• Implementing comparision operators via 'tuple' and 'tie', a good idea?

  - by Xeo

  (Note: tuple and tie can be taken from Boost or C++11.) When writing small structs with only two elements, I sometimes tend to choose a std::pair, as all important stuff is already done for that datatype, like operator< for strict-weak-ordering. The downsides though are the pretty much useless variable names. Even if I myself created that typedef, I won't remember 2 days later what first and what second exactly was, especially if they are both of the same type. This gets even worse for more than two members, as nesting pairs pretty much sucks. The other option for that is a tuple, either from Boost or C++11, but that doesn't really look any nicer and clearer. So I go back to writing the structs myself, including any needed comparision operators. Since especially the operator< can be quite cumbersome, I thought of circumventing this whole mess by just relying on the operations defined for tuple: Example of operator<, e.g. for strict-weak-ordering: bool operator<(MyStruct const& lhs, MyStruct const& rhs){ return std::tie(lhs.one_member, lhs.another, lhs.yet_more) < std::tie(rhs.one_member, rhs.another, rhs.yet_more); } (tie makes a tuple of T& references from the passed arguments.) Edit: The suggestion from @DeadMG to privately inherit from tuple isn't a bad one, but it got quite some drawbacks: If the operators are free-standing (possibly friends), I need to inherit publicly With casting, my functions / operators (operator= specifically) can be easily bypassed With the tie solution, I can leave out certain members if they don't matter for the ordering Are there any drawbacks in this implementation that I need to consider?

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• Can't referr to my get method

  - by chility

  I have this amazing and good looking class: public class SayingsHolder extends Application{ ArrayList<String> SayingsList = new ArrayList<String>(){{ SayingsList.add("1"); SayingsList.add("2"); }}; public ArrayList<String> getSayingsList() { return SayingsList; } } Now I'm trying to call the getSayingsList method inside of my activity's FragmentStatePagerAdapter by: private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter { final SayingsHolder holder = (SayingsHolder).getApplication(); } Everything fine for now, but when I make my code like this: private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter { final SayingsHolder holder = (SayingsHolder).getApplication(); holder.getSayingsList(); } it says: Syntax error on token "getSayingsList", Identifier expected after this token The problem is that holder is not functional at all. What I mean is that when i type the this holder. the getSayingsList is not showing at all. What am I missing here? I know that it is an extremely small issue, but it seems that I can't spot it. My activity extends FragmentActivity if it's important It seems that I'm missing something here. I can't call my method anywhere in my activity. I'm starting a bounty, because I need an example.

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• Standalone Calendar App/Software

  - by Hewittnbut

  We're looking for a standalone (non-cms) calendaring solution to display on the web. It could be open source or a paid service. We're primarily looking for a way to display a calendar on the web complete with when the events are and what the names of the events are. It would be great if it can display in different views like by week, month, year. Month view would be the most important one. We want to keep it as simple as possible. We mainly just want users to view the calendar. The events do not even have to be editable on the end user's side just as long as there is some way for us on the backend to add/delete/import events into the calendar whether it be through .ics (iCal files)/desktop software/via some web interface. We know Google Calendar is around and there is also PHPiCalendar. Are there any other alternatives around? Any suggestions would be appreciated! Thanks!

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• Jquery Mobile is adding text above my "<input type=submit"> automatically, how do i prevent this?

  - by Jack Dalton

  I've just begin work on a mobile version for one of my sites. I've set up my sign up form for my users. It worked fine and the CSS styled it correctly. @using (Html.BeginForm("XXX", "Registration", FormMethod.Post, new { @class = "twitter-sign-in-container" })) { <input type="submit" name="twitter-button" value="Sign in with Twitter" id="twitter-button" /> } Once I added Jquery mobile to the project if found that random unstyled text started to show up. On inspection I found that all input submits where being wrapped in new tags and adding un tagged text == to the inputs "Value": <form action="/registration/xxx" class="twitter-sign-in-container" method="post"> <div class="ui-btn ui-input-btn ui-corner-all ui-shadow"> "Sign in with Twitter" <input type="submit" name="twitter-button" value="Sign in with Twitter" id="twitter-button"> </div> </form> Does anyone have any clue as to why the "sign up with twitter" text is being added, and how i stop it? P.S Less important but I'd also like to know why Jquery wraps form contents in the bellow div.

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• Update all but one result?

  - by Jack M.

  I'm trying to update a table to remove all but the first instance of a group. Basically, I have a table with vehicle data related to an insurance policy. Each policy should only have one power_unit. Everything else should be a towed unit. Unfortunately, a bug has been duplicating power units, and now I need to clean this up. There are ~10k records in the database, and ~4k of them have doubled up power units. The important bits of my table (call it test1 for now) are: +------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+---------+------+-----+---------+----------------+ | id | int(10) | NO | PRI | NULL | auto_increment | | policy_id | int(10) | NO | | NULL | | | power_unit | int(1) | NO | | 0 | | +------------+---------+------+-----+---------+----------------+ And some sample data: +----+-----------+------------+ | id | policy_id | power_unit | +----+-----------+------------+ | 1 | 1 | 1 | | 2 | 1 | 1 | | 3 | 1 | 1 | | 4 | 2 | 1 | | 5 | 2 | 1 | | 6 | 2 | 1 | | 7 | 4 | 1 | | 8 | 4 | 1 | | 9 | 4 | 1 | | 10 | 5 | 1 | | 11 | 5 | 1 | | 12 | 6 | 1 | +----+-----------+------------+ Basically I'd like to end up where policy_id 1 has only one power_unit=1. Same for policy_id 2, 3, 4, etc. For policy_id 6, nothing should change (there is only one entry, and it is a power_unit already). I don't know if this is possible, but it was an intriguing problem for me, so I thought you guys might find it the same.

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• Accessing "pseudo-globals" by their name as a string

  - by rob

  I am now in the process of removing most globals from my code by enclosing everything in a function, turning the globals into "pseudo globals," that are all accessible from anywhere inside that function block. (function(){ var g = 1; var func f1 = function () { alert (g); } var func f2= function () { f1(); } })(); (technically this is only for my "release version", where I append all my files together into a single file and surround them with the above....my dev version still has typically one global per js file) This all works great except for one thing...there is one important place where I need to access some of these "globals" by string name. Previously, I could have done this: var name = "g"; alert (window[name]); and it did the same as alert(g); Now -- from inside the block -- I would like to do the same, on my pseudo-globals. But I can't, since they are no longer members of any parent object ("window"), even though are in scope. Any way to access them by string? Thanks...

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• Is there a Twitter Bootstrap class that means "initially hidden"?

  - by bgp

  Using Bootstrap 3, I have an element on a page I want to show later in response to the user clicking a button. Example: <div id="search_results"> ... gets populated from ajax data later ... </div> <button id="search_button" type="button" class="btn btn-primary pull-right">Search</button> <script> $('#search_button').click(function() { // ... do the call to search // and in the callback: $('#search_results').show(); }); </script> The search_results div should be initially hidden. Is there some normal/best practice way of doing this with bootstrap? Yes, I do realize I can just put style="display:none" on search_results, but is that the best way to do it? It would seem to be a bit better to have a style that semantically means "initially hidden". (NOTE: The hidden or hide classes don't do this as they are !important and show(), toggle(), etc. use an inline style which does not override them, i.e. setting "hidden" as the class makes it unshowable from jQuery.)

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• The perverse hangman problem

  - by Shalmanese

  Perverse Hangman is a game played much like regular Hangman with one important difference: The winning word is determined dynamically by the house depending on what letters have been guessed. For example, say you have the board _ A I L and 12 remaining guesses. Because there are 13 different words ending in AIL (bail, fail, hail, jail, kail, mail, nail, pail, rail, sail, tail, vail, wail) the house is guaranteed to win because no matter what 12 letters you guess, the house will claim the chosen word was the one you didn't guess. However, if the board was _ I L M, you have cornered the house as FILM is the only word that ends in ILM. The challenge is: Given a dictionary, a word length & the number of allowed guesses, come up with an algorithm that either: a) proves that the player always wins by outputting a decision tree for the player that corners the house no matter what b) proves the house always wins by outputting a decision tree for the house that allows the house to escape no matter what. As a toy example, consider the dictionary: bat bar car If you are allowed 3 wrong guesses, the player wins with the following tree: Guess B NO -> Guess C, Guess A, Guess R, WIN YES-> Guess T NO -> Guess A, Guess R, WIN YES-> Guess A, WIN

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• SQL Server: Why use shorter VARCHAR(n) fields?

  - by chryss

  It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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• yet another logic.

  - by Sunil

  I'm working on a research problem out of curiosity and I don't know how to program the logic that I've in mind. Let me explain it to you : I've 4 vectors say for example, v1 = 1 1 1 1 v2 = 2 2 2 2 v3 = 3 3 3 3 v4 = 4 4 4 4 Now what I want to do is to add them combination-wise. i.e v12 = v1+v2 v13 = v1+v3 v14 = v1+v4 v23 = v2+v3 v24 = v2+v4 v34 = v3+v4 Till this step it is just fine. The problem/trick is now, at the end of each iteration I give the obtained vectors into a black box function and it returns only few of the vectors say v12, v13 and v34. Now, I want to add each of these vectors one vector from v1,v2,v3,v4 which it hasn't added before. For example v3 and v4 hasn't been added to v12 so I want to create v123 and v124. similarly for all the vectors like, v12 should become : v123 = v12+v3 v124 = v12+v4 v13 should become : v132 // this should not occur because I already have v123 v134 = v13+v4; v14,v23 and v24 cannot be considered because it was deleted in the black box function so all we have in our hands to work with is v12,v13 and v34. v34 should become : v341 // cannot occur because we have 134 v342 = v34+v2 It is important that I do not do all at one step at the start like for example I can do (4 choose 3) 4C3 and finish it off but I want to do it step by step at each iteration. I've asked a modified version of this question before (without including the black box function) and got answers here. Can anybody tell me how to do it when the black box function is included ? A modification of the previous answer would also be great. Thanks in advance.

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