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  • What does Ruby have that Python doesn't, and vice versa?

    - by Lennart Regebro
    There is a lot of discussions of Python vs Ruby, and I all find them completely unhelpful, because they all turn around why feature X sucks in language Y, or that claim language Y doesn't have X, although in fact it does. I also know exactly why I prefer Python, but that's also subjective, and wouldn't help anybody choosing, as they might not have the same tastes in development as I do. It would therefore be interesting to list the differences, objectively. So no "Python's lambdas sucks". Instead explain what Ruby's lambdas can do that Python's can't. No subjectivity. Example code is good! Don't have several differences in one answer, please. And vote up the ones you know are correct, and down those you know are incorrect (or are subjective). Also, differences in syntax is not interesting. We know Python does with indentation what Ruby does with brackets and ends, and that @ is called self in Python. UPDATE: This is now a community wiki, so we can add the big differences here. Ruby has a class reference in the class body In Ruby you have a reference to the class (self) already in the class body. In Python you don't have a reference to the class until after the class construction is finished. An example: class Kaka puts self end self in this case is the class, and this code would print out "Kaka". There is no way to print out the class name or in other ways access the class from the class definition body in Python. All classes are mutable in Ruby This lets you develop extensions to core classes. Here's an example of a rails extension: class String def starts_with?(other) head = self[0, other.length] head == other end end Ruby has Perl-like scripting features Ruby has first class regexps, $-variables, the awk/perl line by line input loop and other features that make it more suited to writing small shell scripts that munge text files or act as glue code for other programs. Ruby has first class continuations Thanks to the callcc statement. In Python you can create continuations by various techniques, but there is no support built in to the language. Ruby has blocks With the "do" statement you can create a multi-line anonymous function in Ruby, which will be passed in as an argument into the method in front of do, and called from there. In Python you would instead do this either by passing a method or with generators. Ruby: amethod { |here| many=lines+of+code goes(here) } Python: def function(here): many=lines+of+code goes(here) amethod(function) Interestingly, the convenience statement in Ruby for calling a block is called "yield", which in Python will create a generator. Ruby: def themethod yield 5 end themethod do |foo| puts foo end Python: def themethod(): yield 5 for foo in themethod: print foo Although the principles are different, the result is strikingly similar. Python has built-in generators (which are used like Ruby blocks, as noted above) Python has support for generators in the language. In Ruby you could use the generator module that uses continuations to create a generator from a block. Or, you could just use a block/proc/lambda! Moreover, in Ruby 1.9 Fibers are, and can be used as, generators. docs.python.org has this generator example: def reverse(data): for index in range(len(data)-1, -1, -1): yield data[index] Contrast this with the above block examples. Python has flexible name space handling In Ruby, when you import a file with require, all the things defined in that file will end up in your global namespace. This causes namespace pollution. The solution to that is Rubys modules. But if you create a namespace with a module, then you have to use that namespace to access the contained classes. In Python, the file is a module, and you can import its contained names with from themodule import *, thereby polluting the namespace if you want. But you can also import just selected names with from themodule import aname, another or you can simply import themodule and then access the names with themodule.aname. If you want more levels in your namespace you can have packages, which are directories with modules and an __init__.py file. Python has docstrings Docstrings are strings that are attached to modules, functions and methods and can be introspected at runtime. This helps for creating such things as the help command and automatic documentation. def frobnicate(bar): """frobnicate takes a bar and frobnicates it >>> bar = Bar() >>> bar.is_frobnicated() False >>> frobnicate(bar) >>> bar.is_frobnicated() True """ Python has more libraries Python has a vast amount of available modules and bindings for libraries. Python has multiple inheritance Ruby does not ("on purpose" -- see Ruby's website, see here how it's done in Ruby). It does reuse the module concept as a sort of abstract classes. Python has list/dict comprehensions Python: res = [x*x for x in range(1, 10)] Ruby: res = (0..9).map { |x| x * x } Python: >>> (x*x for x in range(10)) <generator object <genexpr> at 0xb7c1ccd4> >>> list(_) [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] Ruby: p = proc { |x| x * x } (0..9).map(&p) Python: >>> {x:str(y*y) for x,y in {1:2, 3:4}.items()} {1: '4', 3: '16'} Ruby: >> Hash[{1=>2, 3=>4}.map{|x,y| [x,(y*y).to_s]}] => {1=>"4", 3=>"16"} Python has decorators Things similar to decorators can be created in Ruby, and it can also be argued that they aren't as necessary as in Python.

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  • Direct3D 11 effect files deprecated?

    - by Toji
    I've been playing around with Direct3D 11 a little bit lately and have been frustrated by the lack of documentation on the basics of the API (such as simple geometry rendering). One of the points of confusion brought on by the sparse documentation is the (apparent) move away from the use of effects for shaders. In D3D11 all of the effect (.fx) support has been removed from the D3DX libraries and buried away in a hard to find (sparsely documented, of course) shared source library. None of the included examples use it, preferring instead to compile HLSL files directly. All of this says to me that Microsoft is trying to get people to stop using the effect file format. Is that true? Is there any documentation of any kind that states that? I'm fine doing it either way, but for years now they've been promoting the .fx format so it seems odd that they would suddenly decide to drop it.

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  • combine two GCC compiled .o object files into a third .o file

    - by ~lucian.grijincu
    How does one combine two GCC compiled .o object files into a third .o file? $ gcc -c a.c -o a.o $ gcc -c b.c -o b.o $ ??? a.o b.o -o c.o $ gcc c.o other.o -o executable If you have access to the source files the -combine GCC flag will merge the source files before compilation: $ gcc -c -combine a.c b.c -o c.o However this only works for source files, and GCC does not accept .o files as input for this command. Normally, linking .o files does not work properly, as you cannot use the output of the linker as input for it. The result is a shared library and is not linked statically into the resulting executable. $ gcc -shared a.o b.o -o c.o $ gcc c.o other.o -o executable $ ./executable ./executable: error while loading shared libraries: c.o: cannot open shared object file: No such file or directory $ file c.o c.o: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically linked, not stripped $ file a.o a.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped

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  • Spring online repository for Maven

    - by Fortyrunner
    I've just installed Maven2 for the first time. By default it pulls down a few useful jars into a local project: jakarta-commons, junit etc. I wanted to pull in the latest Spring release (2.5.6 at the time of writing). But the online repositories I looked at (iBiblio and Maven) only had much older versions of Spring libraries. Are there any other repositories that are kept up to date? What is the best practice here; can we maintain them ourselves? I would be prepared to help out maintaining this stuff!

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  • Multithreading in Lua

    - by RCIX
    I was having a discussion with my friend the other day. I was saying how that, in pure Lua, you couldn't build a preemptive multitasking system. He claims you can, because of the following reason: Both C and Lua have no inbuilt threading libraries [OP's note: well, Lua technically does, but AFAIK it's not useful for our purposes]. Windows, which is written in mostly C(++) has pre-emptive multitasking, which they built from scratch. Therefore, you should be able to do the same in Lua. The big problem i see with that is that the main way preemptive multitasking works (to my knowledge) is that it generates regular interrupts which the manager uses to get control and determine what code it should be working on next. I also don't think Lua has any facility that can do that. My question is: is it possible to write a pure-Lua library that allows people to have pre-emptive multitasking?

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  • Choosing between ExtJS and YUI based of application parameters.

    - by Kabeer
    Hello. I need help in taking call to choose between Ext JS and YUI libraries. Here are the key factors I have derived from my application requirements & development process: Complex, windows forms like controls Widgets, Layouts, Utilities Inter widget communication Easy to extend Easy to learn Intuitive & concise coding Strong exception handling Active support / community To update with upcoming technologies (HTML5, etc.) Skins & Themes to be easy to change Skins & Themes to support variety (a text box for different context to appear differently) Support & Utilities for standard protocols (XmlHttp, JSON) Good performance (responsive) Cost is not crucial, but I don't mind saving :)

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  • How to figure out optimal C / Gamma parameters in libsvm?

    - by Cuga
    I'm using libsvm for multi-class classification of datasets with a large number of features/attributes (around 5,800 per each item). I'd like to choose better parameters for C and Gamma than the defaults I am currently using. I've already tried running easy.py, but for the datasets I'm using, the estimated time is near forever (ran easy.py at 20, 50, 100, and 200 data samples and got a super-linear regression which projected my necessary runtime to take years). Is there a way to more quickly arrive at better C and Gamma values than the defaults? I'm using the Java libraries, if that makes any difference.

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  • XSLT transformations in Ruby and JRuby

    - by jpatokal
    Simple question: are there any solid XSLT libraries that work in both Ruby and JRuby? REXML works in both, but does not have XSLT support. ruby-xslt doesn't work in JRuby. The latest Nokogiri betas do support JRuby, but the support is still buggy and throws occasional NullPointerExceptions for XML input that works fine in Ruby. (In particular, any transforms that don't result in valid XML cause it to barf, even if xsl:output is set to 'text'!) JXslt is just a wrapper for Java's Xalan/Saxon and doesn't work in Ruby. Please tell me I'm missing something?

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  • Good Perlin noise resources/implementation?

    - by Chumpy
    Are there any good resources out there detailing Perlin noise generation? I understand that most languages have noise generating libraries available, but I'm interested in creating my own for fun/experience. I've already looked at this, which seems pretty popular, but it only gives an in-depth explanation of one dimensional noise. Google searches have been relatively unhelpful so far, as most of them focus on applications instead of how to create a generator. Books and/or websites are welcome, even if their focus is not the generation itself so long as it gives a thorough explanation of an implementation, or at least the concepts involved so I can "discover" my own.

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  • Can I partition the C# System.Threading.ThreadPool?

    - by Drew Shafer
    I love ThreadPool. It makes my life better. However, my love may have quietly turned into an abusive relationship that I need to escape from, so I need some advice from my SO brothers (and presumably sisters, although I haven't seen any actual evidence of that yet). My basic problem is that I have several different libraries that are all using the threadpool in an uncoordinated way, and running out of threads is a possibility. I was hoping there was some way I could partition the ThreadPool up so I could give a certain class 1 thread, another 20 threads, another 5 threads, and so on. I know I could write my own ThreadPool implementation. I don't want to do that, because I'm lazy. So, is there a simple solution already out there? Currently I'm constrained to using the 3.5 CLR. I know a lot of this stuff becomes easier in 4.0.

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  • ruby memory leak Gdk::PixbufLoader

    - by Reed Debaets
    So I'm beginning to wonder how leaky the gnome2 libraries for ruby1.8.6 are. #!/usr/bin/env ruby require 'gtk2' while true sleep 0.1 pixbuf = Gdk::PixbufLoader.new pixbuf = nil end this leaks about 16kb/sec according to watch -n 1 ps -o rss -p <process id> This is compounded if you start trying to write a chunk of large chunks of image data to it using pixbuf.last_write img_data Any ideas how to get around this (and the second issue)? I need to update image data within my code but it seems like anything that ends up using a pixbuf leaks like a sieve.

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  • In C# should I use uint or int for values that are never supposed to be negative?

    - by Hamish Grubijan
    Suppose that the MaxValue of (roughly :) ) 2^31 vs 2^32 does not matter. On one hand, using uint seems nice because it is self-explanatory, it indicates (and promises?) that some value may never be negative. However, int is more common, and a cast is often inconvenient. One can just use int and always supplement it with code contracts (everyone has moved to .Net 4.0 by now, right?) Standard libraries do use int for Length and Size properties, even though those should never be negative. So, is it obvious to you that int is better than uint most of the time, or is it more complicated? Please ask questions if you find that this question is not clearly stated. Thanks.

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  • Client/JS Framework for "Unsaved Data" Protection?

    - by Kevin Dostalek
    Hey all- we have a typical web application that is essentially a data entry application with lots of screens some of which have some degree of complexity. We need to provide that standard capability on making sure if the user forgets to click the "Save" button before navigating away or closing their browser they get a warning and can cancel (but only when there is unsaved or dirty data). I know the basics of what I've got to do-- in fact I'm sure I've done it all before over the years (tie in to onbeforeunload, track the "dirty" state of the page, etc...) but before I embark on coding this YET AGAIN, does anyone have some suggestions for libraries already out there (free or otherwise) that will help out? Thanks!

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  • What XSLT processor should I use for Java transformation?

    - by Artic
    What XSLT processor should I use for Java transformation? There are SAXON, Xalan and TrAX. What is the criteria for my choice? I need simple transformation without complicated logical transformations. Need fast and easy to implement solution. APP runs under Tomcat, Java 1.5. I have some jaxp libraries and could not understand what is the version of jaxp used. Thanks in advance. Best regards.

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  • How to compare two maps by their values

    - by lewap
    How to compare two maps by their values? I have two maps containing equal values and want to compare them by their values. Here is an example: Map a = new HashMap(); a.put("f"+"oo", "bar"+"bar"); a.put("fo"+"o", "bar"+"bar"); Map b = new HashMap(); a.put("f"+"oo", "bar"+"bar"); a.put("fo"+"o", "bar"+"bar"); System.out.println("equals: " + a.equals(b)); // obviously false .... what to call to obtain a true? Obviously, to implement a comparison it not difficult, it is enough to compare all keys and their associated values. I don't believe I'm the first one to do this, so there must be already a library functions either in java or in one of the jakarta.commons libraries. Thanks

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  • Multiple complete HTTP requests stuck in TCP CLOSE_WAIT state

    - by Sean Owen
    I have a Java and Tomcat-based server application which initiates many outbound HTTP requests to other web sites. We use Jakarta's HTTP Core/Client libraries, very latest versions. The server locks up at some point since all its worker threads are stuck trying to close completed HTTP connections. Using 'lsof' reveals a bunch of sockets stuck in TCP CLOSE_WAIT state. This doesn't happen for all, or even most connections. In fact, I saw it before and resolved it by making sure to set the Connection: Close response header. So that makes me think it may be bad behavior of remote servers. It may have come up again since I moved the app to a totally new service provider -- different OS, network situation. But, I am still at a loss as to what I could do, if anything, to work around this. Some poking around on the internet didn't turn up anything I'm not already doing. Just thought I'd ask if anyone has seen and solved this?

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  • When is JavaScript's eval() not evil?

    - by Richard Turner
    I'm writing some JavaScript to parse user-entered functions (for spreadsheet-like functionality). Having parsed the formula I could convert it into JavaScript and run eval() on it to yield the result. However, I've always shied away from using eval() if I can avoid it because it's evil (and, rightly or wrongly, I've always thought it is even more evil in JavaScript because the code to be evaluated might be changed by the user). Obviously one has to use eval() to parse JSON (I presume that JS libraries use eval() for this somewhere, even if they run the JSON through a regex check first), but when else, other than when manipulating JSON, it is OK to use eval()?

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  • No network packets sent immediately after quick physical disconnect and reconnect.

    - by Hans
    I am using Boost's ASIO libraries to establish a UDP connection to a remote server. To make sure the connection is active, every second a keep-alive message is sent to the server. I have noticed that if I unplug the network cable and reinsert it quickly, the first 2 or 3 keep-alive messages after the reinsert are never sent. I tested this by running wire-shark on the server. I have seen it take up to 5 seconds before the client starts sending out network traffic again. The client is running under Linux (2.6.2), if that helps.

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  • C++: what regex library should I use?

    - by Stéphane
    I'm working on a commercial (not open source) C++ project that runs on a linux-based system. I need to do some regex within the C++ code. (I know: I now have 2 problems.) QUESTION: What libraries do people who regularly do regex from C/C++ recommend I look into? A quick search has brought the following to my attention: 1) Boost.Regex (I need to go read the Boost Software License, but this question is not about software licenses) 2) C (not C++) POSIX regex (#include <regex.h>, regcomp, regexec, etc.) 3) http://freshmeat.net/projects/cpp_regex/ (I know nothing about this one; seems to be GPL, therefore not usable on this project) Thanks.

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  • Should I update an application when a used framework release a new version?

    - by Alex
    I have an application that use several libraries and frameworks, should I update my application to use the latest version of those frameworks when a new stable version is available? For example, migrate from python 2.x to python 3.x, or from spring 2.5 to spring 3.0, but the question es very general, not language specific. If I keep the application updated to use the latest stable frameworks versions then I will have new features available in case I need them. If I don't, then may be in a future I will need to do the update and it will be a lot of work to update the application. Is there any best practice about this?

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  • Own data format for the iPhone

    - by Stefan
    Hi, I would like to create my own data format for an iPhone app. The files should be similar structured as e.g. Apple's iWork files (.pages). That means, I have a folder with some files in it: The file 'Juicy.fruit' contains: Fruits ---> Apple.xml ---> Banana.xml ---> Pear.xml ---> PreviewPicture.png This folder "Fruits" should be packed in a handy file 'Juicy.fruit'. Compression isn't necessary. How could I achieve this? I've discovered some open source ZIP-libraries. However, I would like to to build my own data format with the iPhones built-in libs (if possible). Best regards, Stefan

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  • using property file along with config file to be used with mxmlc

    - by whoopy_whale
    Hi, I'm trying to run mxmlc in the following manner. mxmlc -load-config+=mycfg.xml C:\\projects\\src\\main.mxml -output myswf.swf In the config file, I want to keep some values configurable, for example the paths of the external libraries. Is it possible to include a property file into the config file and use it as {property_name} in the config file? Or is it possible to pass certain arguments from the command line itself that will override/replace the corresponding values in the config file, like the -D option in the ant command? Please provide your suggestions.

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  • Programmatic resource monitoring per process in Linux

    - by tuxx
    Hi, I want to know if there is an efficient solution to monitor a process resource consumption (cpu, memory, network bandwidth) in Linux. I want to write a daemon in C++ that does this monitoring for some given PIDs. From what I know, the classic solution is to periodically read the information from /proc, but this doesn't seem the most efficient way (it involves many system calls). For example to monitor the memory usage every second for 50 processes, I have to open, read and close 50 files (that means 150 system calls) every second from /proc. Not to mention the parsing involved when reading these files. Another problem is the network bandwidth consumption: this cannot be easily computed for each process I want to monitor. The solution adopted by NetHogs involves a pretty high overhead in my opinion: it captures and analyzes every packet using libpcap, then for each packet the local port is determined and searched in /proc to find the corresponding process. Do you know if there are more efficient alternatives to these methods presented or any libraries that deal with this problems?

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  • Running a shellscript from a C++ application and check if it succeeds

    - by Koning Baard
    I am creating an interpreter for my extension to HQ9+, which has the following extra command called V: V: Interpretes the code as Lua, Brainfuck, INTERCAL, Ruby, ShellScript, Perl, Python, PHP in that order, and if even one error has occoured, run the HQ9+-ABC code again most of them have libraries, BF and INTERCAL can be interpreted without a library, but the problem lies in ShellScript. How can I run a shellscript from my C++ application ( =the HQ9+-ABC interpreter) and when it's done, get the error code (0 = succeded, all others = failed)? So something like this: system(".tempshellscript738319939474"); if(errcode != 0) { (rerun code); } can anyone help me? Thanks

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  • Entity-attribute-value model using codeigniter / php

    - by John Stewart
    SO I am trying to create a way to structure my database to be able customize forms. I looked into EAV pattern and here is my db structure: Table form - form_id - form_name - form_added_on - form_modified_at Table: form_fields - field_id - form_id - field_type (TEXT, RADIO etc..) - field_default_value - field_required Table: form_data - data_id - field_id - form_id - field_value so now I can store any custom form into the database and if I want to get the values for an individual form I can simply join it by "form_id" .. the problem: I want to be able to search through all the forms for a specific field value. How can I do that with EAV model? Also, I thought about just storing the custom data as a serialized (JSON) object but then I am not sure how can I query that data. Please note that I am using Codeigniter with MYSQL. So if conversation can use Codeigniter libraries if needed.

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