leonid shevtsov - Page 2

How to parse an argument without a name with Ruby's optparse

- by Leonid Shevtsov

I need to parse a command line like script.rb <mandatory filename> [options] with optparse. Sure I can write some custom code to handle the filename, then pass ARGV to optparse, but maybe there's a simpler way to do it? EDIT: there's another hacky way to parse such a command line, and that is pass '--mandatory-filename ' + ARGV to optparse, then handle the --mandatory-filename option.

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How to make the class constructor private in Ruby?

- by Leonid Shevtsov

class A private def initialize puts "wtf?" end end A.new #still works and calls initialize and class A private def self.new super.new end end doesn't work altogether So what's the correct way? I want to make new private and call it via a factory method.

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Are there any solutions for translating measurement units on Rails?

- by Leonid Shevtsov

I'd like to implement measurement unit preferences in a Ruby on Rails app. For instance, the user should be able to select between displaying distances in miles or in kilometers. And, obviously, not only displaying, but entering values, too. I suppose all values should be stored in one global measurement system to simplify calculations. Are there any drop-in solutions for this? Or should I maybe write my own?

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1-st level routes for multiple resources in Rails

- by Leonid Shevtsov

I have a simple SEO task. There's a City model and a Brand model, and I have to create 1st-level URLs for both (e.g. site.com/honda and site.com/boston). What's the preferred routing/controller combination to do this in Rails? I can only think of map.connect '/:id', :controller => 'catchall', :action => 'index' class CatchallController < ApplicationController def index if City.exists?(:slug => params[:id]) @city = City.find_by_slug!(params[:id]) render 'cities/show' else @brand = Brand.find_by_slug!(params[:id]) render 'brands/show' end end end but it seems to be very un-Rails to put such logic into the controller. (Obviously I need to make sure that the slugs don't overlap in the models, that's done).

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What's the best way to run a Linux virtual server in Windows 7?

- by Leonid Shevtsov

I need a virtual server for web development, it'll host Apache+Postgres+Ruby+something else. What's the most effective software to run such a server? (ie with least virtualization overhead) Is there a way to run Linux as as service? I use VirtualBox at the moment, but it's inconvenient in some ways, such as it needs an emulator window open which also captures keyboard input when alttabbed into. (Also, coLinux hangs at boot on my machine, so it's probably not an option)

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Oracle Database character set issue with the audit tables on Debian

- by Leonid Shirmanov

I've got Oracle XE installed on Debian linux and the character set is configured to AL32UTF8. There are several client applications that connects to a database from Windows with the different locales - French etc, not English. That's ok with all the client data these applications put into database, nothing converted and text data in French represents correctly. But texts in audit tables looks like '??????' if contains any not-english character. I suppose this is because audit records go to database in the different locale and it's not dependent on the client's globalization/locale settings. How this globalization issue can be fixed? thanks!

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Output is different for R-value and L-value. Why?

- by Leonid Volnitsky

Can someone explain to me why output for R-value is different from L-value? #include <iostream> #include <vector> using namespace std; template<typename Ct> struct ct_wrapper { Ct&& ct; // R or L ref explicit ct_wrapper(Ct&& ct) : ct(std::forward<Ct>(ct)) { std::cout << this->ct[1];}; }; int main() { // L-val vector<int> v{1,2,3}; ct_wrapper<vector<int>&> lv(v); cout << endl << lv.ct[0] << lv.ct[1] << lv.ct[2] << endl; // R-val ct_wrapper<vector<int>&&> rv(vector<int>{1,2,3}); cout << endl << rv.ct[0] << rv.ct[1] << rv.ct[2] << endl; } Output (same for gcc48 and clang32): 2 123 2 003

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Running GUI application in the Windows service mode

- by Leonid

I'm writing a server running as a Windows service that by request invokes Firefox to generate a pdf snapshot of a webpage. I know it is a bad idea to run a GUI program in service mode, but the server nature of my program restricts from running it in the user mode. Running a user-level 'proxy' also is not an option, since there might be no interactive user logged-in on the machine with the server running. In my experiments Firefox successfully produced pdf when the service was running under a user account that was already logged-in. Obviously it didn't work in other cases: for Local System and user accounts that weren't logged-in. Under LocalSystem with 'Allow service to interact with desktop' option enabled I could see the Firefox started that reports that it's unable to find a printer. Since it wouldn't be practical to require an opened user session for the pdf server to run, is there any workaround for this except running the whole thing from a virtual machine?

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Why Flash can't be rendered in a Windows Service?

- by Leonid

I'm trying to solve a similar problem as was described here - to create a Windows Service for taking snapshots of rich webpages (html+js+flash) and saving them to a PDF file. The bundle Firefox+cmdlnprint did the trick for me. I wrote a simple program running as a service that invokes Firefox to make a PDF. All seems well, the PDF gets created, but Flash is completely missing. Although, when started not as a service, Flash renders just fine. Can anyone shed a light on what blocks Flash from rendering and if there's a workaround? thanks!

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Running Firefox in the Windows service mode

- by Leonid

I'm writing a server running as a Windows service that by request invokes Firefox to generate a pdf snapshot of a webpage. I know it is a bad idea to run a GUI program in service mode, but the server nature of my program restricts from running it in the user mode. Running a user-level 'proxy' also is not an option, since there might be no interactive user logged-in on the machine with the server running. In my experiments Firefox successfully produced pdf when the service was running under a user account that was already logged-in. Obviously it didn't work in other cases: for Local System and user accounts that weren't logged-in. Under LocalSystem with 'Allow service to interact with desktop' option enabled I could see the Firefox started that reports that it's unable to find a printer. Since it wouldn't be practical to require an opened user session for the pdf server to run, is there any workaround for this except running the whole thing from a virtual machine?

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What is in your Mathematica tool bag?

- by Timo

We all know that Mathematica is great, but it also often lacks critical functionality. What kind of external packages / tools / resources do you use with Mathematica? I'll edit (and invite anyone else to do so too) this main post to include resources which are focused on general applicability in scientific research and which as many people as possible will find useful. Feel free to contribute anything, even small code snippets (as I did below for a timing routine). Also, undocumented and useful features in Mathematica 7 and beyond you found yourself, or dug up from some paper/site are most welcome. Please include a short description or comment on why something is great or what utility it provides. If you link to books on Amazon with affiliate links please mention it, e.g., by putting your name after the link. Packages: LevelScheme is a package that greatly expands Mathematica's capability to produce good looking plots. I use it if not for anything else then for the much, much improved control over frame/axes ticks. David Park's Presentation Package ($50 - no charge for updates) Tools: MASH is Daniel Reeves's excellent perl script essentially providing scripting support for Mathematica 7. (This is finally built in as of Mathematica 8 with the -script option.) Resources: Wolfram's own repository MathSource has a lot of useful if narrow notebooks for various applications. Also check out the other sections such as Current Documentation, Courseware for lectures, and Demos for, well, demos. Books: Mathematica programming: an advanced introduction by Leonid Shifrin (web, pdf) is a must read if you want to do anything more than For loops in Mathematica. Quantum Methods with Mathematica by James F. Feagin (amazon) The Mathematica Book by Stephen Wolfram (amazon) (web) Schaum's Outline (amazon) Mathematica in Action by Stan Wagon (amazon) - 600 pages of neat examples and goes up to Mathematica version 7. Visualization techniques are especially good, you can see some of them on the author's Demonstrations Page. Mathematica Programming Fundamentals by Richard Gaylord (pdf) - A good concise introduction to most of what you need to know about Mathematica programming. Undocumented (or scarcely documented) Features: How to customize Mathematica keyboard shortcuts. See this question. How to inspect patterns and functions used by Mathematica's own functions. See this answer How to achieve Consistent size for GraphPlots in Mathematica? See this question.

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