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• Any way to have delayed_job execute some run-once code at startup and use across all jobs?

  - by Rob Cameron

  So I've got a delayed_job task that pushes some info to an XMPP server. Ideally you create a connection to XMPP once and then constantly push data to it, rather than creating a new connection every time you have some data to send. Is there any kind of facility in delayed_job for running a sort of 'setup' method when a worker starts, have it set some instance variables (like the XMPP connection object) that can then be used by all the jobs that come up? It's okay if each worker runs its own setup method. I just don't want every job (thousands per day) connecting to the XMPP server from scratch every time. Thanks for any help!

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• when is java faster than c++ (or when is JIT faster then precompiled)?

  - by kostja

  I have heard that under certain circumstances, Java programs or rather parts of java programs are able to be executed faster than the "same" code in C++ (or other precompiled code) due to JIT optimizations. This is due to the compiler being able to determine the scope of some variables, avoid some conditionals and pull similar tricks at runtime. Could you give an (or better - some) example, where this applies? And maybe outline the exact conditions under which the compiler is able to optimize the bytecode beyond what is possible with precompiled code? NOTE : This question is not about comparing Java to C++. Its about the possibilities of JIT compiling. Please no flaming. I am also not aware of any duplicates. Please point them out if you are.

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• PHP Sessions - Locking and Sharing questions

  - by Nuno Peralta

  Hi, I would like to know if it is possible to read $_SESSION attributes without locking it. Currently, session_start() locks SESSION, that means other PHP processes will wait until it is unlocked. But, some processes just want to get some $_SESSION variables, not to write on them. Is that possible to implement some function like session_get(string $id) which doesn't lock SESSION? Also, it is possible to share SESSIONs between browsers, once the user is logged in the same account, for example, using session_id('shared_vars_of_'.$userid). But, is that secure? Is this discouraged? Thanks, Nuno

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• javascript table - update on data request

  - by flyingcrab

  Hi, I am trying to update a table based on a json request. The first update / draw works fine - but any subsequent changes to the variables (the start and end date) do not show up - even though the json pulled from the server seems to be correct (according to firebug). AFAIK the code below should re-initialize everything - no sure what is going on (I'm using the Google vizulization api)? function handleQueryResponse(response) { if (response.isError()) { //alert('Error in query: ' + response.getMessage() + ' ' + response.getDetailedMessage()); return; } visualization = new google.visualization.Table(document.getElementById('visualization')); visualization.draw(response.getDataTable(), null); } One more thing: I'm working on a page that displays textbased tables and currently trying to decide between the google table (viz api) and a jQuery alternative I came across jqGrid any good ones I am missing?

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• Why doesn't CSS support constants?

  - by Adiel Mittmann

  CSS has never supported constants or variables directly. Whenever I'm writing code like this: span.class1 { color: #377fb6; } div.class2 { border: solid 1px #377fb6; /* Repeated color */ } I wonder why such a seemingly simple feature has never made it into the standard. What could be hard about implementing a scheme whereby we could avoid repetition, something like this: $theme_color1: #377fb6; span.class1 { color: $theme_color1; } div.class2 { border: solid 1px $theme_color1; } I know there are workarounds, like using a class for each color or generating CSS code from templates, but my question is: given that CSS is so rich and complex, why weren't CSS constants ever introduced?

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• Corrupted image if variable is not static

  - by Jaka Jancar

  I'm doing the following: static GLfloat vertices[3][3] = { {0.0, 1.0, 0.0}, {1.0, 0.0, 0.0}, {-1.0, 0.0, 0.0} }; glColor4ub(255, 0, 0, 255); glEnableClientState(GL_VERTEX_ARRAY); glVertexPointer(3, GL_FLOAT, 0, vertices); glDrawArrays(GL_TRIANGLES, 0, 9); glDisableClientState(GL_VERTEX_ARRAY); This works ok: However, if I remove static from vertices and therefore re-create the data on the stack on each rendering, I get the following: This happens both on the simulator and on the device. Should I be keeping the variables around after I call glDrawArrays?

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• Xcodebuild failing to pick up environment values from project file?

  - by egrunin

  I'm using Xcode 3.2.6, MacOSX. I have a globally visible environment setting: ICU_SRC=~/Documents/icu/source This really is an environment setting, it's set at login time. When I open up Terminal, it's there. In my project, under Header Search Paths I've added this: $(ICU_SRC)/i18n $(ICU_SRC)/common These expand correctly when I compile inside the IDE. When I look at the build results, I see this: -I/Users/eric.grunin/Documents/icu/source/i18n -I/Users/eric.grunin/Documents/icu/source/common When I build from the command line, however, it fails. What I see is this: -I/i18n -I/common Here's the command I'm using to compile: /usr/bin/env -i xcodebuild -project my_project.xcodeproj -target "my_program" -configuration Release -sdk macosx10.6 build What am I doing wrong? Edited to add: Apple explains Setting environment variables for user processes

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• Create a triangle out of stars using only recursion

  - by Ramblingwood

  I need to to write a method that is called like printTriangle(5);. We need to create an iterative method and a recursive method (without ANY iteration). The output needs to look like this: * ** *** **** ***** This code works with the iterative but I can't adapt it to be recursive. public void printTriangle (int count) { int line = 1; while(line <= count) { for(int x = 1; x <= line; x++) { System.out.print("*"); } System.out.print("\n"); line++; } } I should not that you cannot use any class level variables or any external methods. Thanks.

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• Inline function and calling cost in C

  - by Eonil

  I'm making a vector/matrix library. (GCC, ARM NEON, iPhone) typedef struct{ float v[4]; } Vector; typedef struct{ Vector v[4]; } Matrix; I passed struct data as pointer to avoid performance degrade from data copying when calling function. So I thought designed function like this: void makeTranslation(const Vector* factor, Matrix* restrict result); But, if function is inline, is there any reason to pass values as pointer for performance? Do those variables copied too? How about register and caches? inline Matrix makeTranslation(Vector factor) __attribute__ ((always_inline)); How do you think about calling costs of each cases?

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• R: how can I concatenate a list?

  - by John

  I'm trying to produce a single variable which is a concatenation of two chars e.g to go from "p30s4" "p28s4" to "p30s4 p28s4". I've tried cat and paste as shown below. Both return empty variables. What am I doing wrong? > blah = c("p30s4","p28s4") > blah [1] "p30s4" "p28s4" > foo = cat(blah) p30s4 p28s4 > foo NULL > foo = paste(cat(blah)) p30s4 p28s4 > foo character(0)

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• How to insert many rows of data from arrays/lists to SQL Server (DataSet, DataTable)

  - by Kamil

  I need little help with transferring data from variables, arrays, lists to my SQL Server. Im not bad in SQL, but im not familiar with DataSet, DataTable objects. My data is now stored in list of strings (List). Every string in that list looks similar to this: QWERTY,19920604,0.91,0.35,0.34,0.35,343840 There are about 900000 rows like this. Target datatypes in SQL Server: BIGINT (primary key, im not inserting it, its identity(1,1)) VARCHAR(10), DATE, DECIMAL(10,2), DECIMAL(10,2), DECIMAL(10,2), DECIMAL(10,2), INT How to convert that data to SQL Server data types? How to insert that data into SQL Server? Also i need some progress bar updates between inserts. I could do this using old-fashion SQL command, but i have learn more modern way :)

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• C++ word to bytes

  - by Vit

  Hi, I tried to read CPUID using assembler in C++. I know there is function for it in , but I want the asm way. So, after CPUID is executed, it should fill eax,ebx,ecx registers with ASCII coded string. But my problem is, since I can in asm adress only full, or half eax register, how to break that 32 bits into 4 bytes. I used this: #include <iostream> #include <stdlib.h> int main() { _asm { cpuid /*There I need to mov values from eax,ebx and ecx to some propriate variables*/ } system("PAUSE"); return(0); }

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• Posting null values via AJAX

  - by nickf

  Using the jQuery $.post function, if you send a null value, it arrives at the server side as "null". Example: Javascript: $.post('test.php', { foo : null }); PHP: var_dump($_POST['foo']); // string(4) "null" I understand why this is so, but was wondering the best way to work around the limitation? Should you: Loop through all the variables in JS before you send them and replace with an empty string? Interpret "null" as null on the server side? Don't send the variable at all? Something else?

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• Question about the lifecycle of a simple Android application

  - by jul

  Hi, I've got a simple application with 3 activities: -the first contains a search box which calls a web service and show the results (restaurants) below in a listview -when a restaurant is clicked another activity is started showing the description of the restaurant and a button "show map" -when the button "show map" is clicked, guess what, the map is shown in a third activity. All the data is loaded in the first activity by a web service (restaurant descriptions and coordinates), and data required by each activity is passed in a bundle using "intent.putExtra". Now everything seems to run smoothly when clicking on the back button (eg. clicking on the back button from the map resumes the "restaurant description" activity with all data set properly), while I haven't done anything about the lifecycle yet. Why? Are all variables saved automatically? Should I use onSaveInstanceState() and onRestoreInstanceState() anyway? Thanks Jul

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• Issue with plotting daily data using ggplot

  - by user1723765

  I tried to plot daily data from 9 variables in ggplot, but the graph I get cannot handle the date variable properly. The x axis is unreadable and its impossible to read the plot. I'm guessing there's an issue with the handling of dates. Here's the data: https://dl.dropbox.com/u/22681355/su.csv Here's the code I've been using: su=read.csv(file="su.csv", head=TRUE) meltdf=melt(su) ggplot(meltdf, aes(x=Date, y=value, colour=variable, group=variable))+geom_line() and here's the output: https://dl.dropbox.com/u/22681355/output.jpg here's the same plot done in excel, why does it look completely different?

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• JS function returning another function

  - by Michael

  I want to understand about variables, that has been used in returning function. This is example code Prototype = {} Prototype.F = { bind: function() { var args = arguments, __method = args.shift(), object = args.shift(); return function() { return __method.apply(object, args.concat(arguments)); } } } function ObjectA() { ... this.addListener = Prototype.F.bind(this.eventSource.addListener, this.eventSource); ... } var a = ObjectA(); a.addListener(this); // assuming 'this' here will point to some window object As I understand the returning function in F() is not evaluated until it's called in the last line. It's ok to accept. So addListener will hold a function body containing 'apply'. But what I don't understand, when addListener is called, what kind of parameters it is going to have? particularly _method and args will always be uninitialized?

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• For what purpose does java have a float primitive type?

  - by Roman

  I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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• local match kickoff time

  - by Usagi Dreamy

  I'm working on a sports website and need to convert the server's match start time to local match start time. After much googling, I figured the fastest and most accurate way is to get the GMT offset value in JavaScript. The trouble is, I can't pass the GMT offset value to PHP. I've tried using both the PHP session and cookie variables, but both are always empty. The website doesn't require a user account, so there isn't any stored GMT value in the database. I'm trying to auto-detect each user's local timezone every time he/she visits the website, and then calculate the local match start time based on the timezone offset. Can someone please advise me? Thanks.

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• A pragmatic view on private vs public

  - by Denis Gorbachev

  Hello everybody! I've always wondered on the topic of public, protected and private properties. My memory can easily recall times when I had to hack somebody's code, and having the hacked-upon class variables declared as private was always upsetting. Also, there were (more) times I've written a class myself, and had never recognized any potential gain of privatizing the property. I should note here that using public vars is not in my habit: I adhere to the principles of OOP by utilizing getters and setters. So, what's the whole point in these restrictions?

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• Encoding gives "'ascii' codec can't encode character … ordinal not in range(128)"

  - by user140314

  I am working through the Django RSS reader project here. The RSS feed will read something like "OKLAHOMA CITY (AP) — James Harden let". The RSS feed's encoding reads encoding="UTF-8" so I believe I am passing utf-8 to markdown in the code snippet below. The em dash is where it chokes. I get the Django error of "'ascii' codec can't encode character u'\u2014' in position 109: ordinal not in range(128)" which is an UnicodeEncodeError. In the variables being passed I see "OKLAHOMA CITY (AP) \u2014 James Harden". The code line that is not working is: content = content.encode(parsed_feed.encoding, "xmlcharrefreplace") I am using markdown 2.0, django 1.1, and python 2.4. What is the magic sequence of encoding and decoding that I need to do to make this work? Thanks.

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• How to get the first non-null value in Java?

  - by froadie

  Is there a Java equivalent of SQL's COALESCE function? That is, is there any way to return the first non-null value of several variables? e.g. Double a = null; Double b = 4.4; Double c = null; I want to somehow have a statement that will return the first non-null value of a, b, and c - in this case, it would return b, or 4.4. (Something like the sql method - return COALESCE(a,b,c)). I know that I can do it explicitly with something like: return a != null ? a : (b != null ? b : c) But I wondered if there was any built-in, accepted function to accomplish this.

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• Static vs Non Static constructors

  - by Neil N

  I can't think of any reasons why one is better than the other. Compare these two implementations: public class MyClass { public myClass(string fileName) { // some code... } } as opposed to: public class MyClass { private myClass(){} public static Create(string fileName) { // some code... } } There are some places in the .Net framework that use the static method to create instances. At first I was thinking, it registers it's instances to keep track of them, but regular constructors could do the same thing through the use of private static variables. What is the reasoning behind this style?

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• Translate imperative control flow with break-s/continue-s to haskell

  - by dorserg

  Consider the following imperative code which finds the largest palindrome among products of 3-digit numbers (yes, it's the one of the first tasks from "Project of [outstanding mathematician of 18th century]" site): curmax = 0 for i in range(999,100): for j in range(999,100): if ((i*j) < curmax): break if (pal(i*j)): curmax = i*j break print curmax As I'm learning Haskell currently, my question is, how do you translate this (and basically any imperative construct that contains something more complex than just plain iteration, e.g. breaks, continues, temporary variables and all this) to Haskell? My version is maxpal i curmax | i < 100 = curmax | otherwise = maxpal (i-1) (innerloop 999) where innerloop j | (j < 100) || (p < curmax) = curmax | pal p = p | otherwise = innerloop (j-1) where p = i*j main = print $ maxpal 999 0 but this looks like we're still in imperative uglytown. So what could you advise, what are the approaches of dealing with such cases FP-style?

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• Body class for controller in Rails app.

  - by Vincent

  Currently I have this in my layout: <body class="<%= controller.controller_name %>"> I want to add an additional class that will be the same for all actions in any controller where it's set, something like: class SomeController < ApplicationController body_class 'page' ... end class AnotherController < ApplicationController body_class 'page' ... end Which will result in: <body class="some page"> <body class="another page"> What would be the easiest way to achieve this? Can I use controller class variables for this?

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• How does an interpreter switch scope?

  - by Dox

  I'm asking this because I'm relatively new to interpreter development and I wanted to know some basic concepts before reinventing the wheel. I thought of the values of all variables stored in an array which makes the current scope, upon entering a function the array is swapped and the original array put on some sort of stack. When leaving the function the top element of the "scope stack" is popped of and used again. Is this basically right? Isn't swapping arrays (which means moving around a lot of data) not very slow and therefore not used by modern interpreters?

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