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  • NoSQL for filesystem storage organization and replication?

    - by wheaties
    We've been discussing design of a data warehouse strategy within our group for meeting testing, reproducibility, and data syncing requirements. One of the suggested ideas is to adapt a NoSQL approach using an existing tool rather than try to re-implement a whole lot of the same on a file system. I don't know if a NoSQL approach is even the best approach to what we're trying to accomplish but perhaps if I describe what we need/want you all can help. Most of our files are large, 50+ Gig in size, held in a proprietary, third-party format. We need to be able to access each file by a name/date/source/time/artifact combination. Essentially a key-value pair style look-up. When we query for a file, we don't want to have to load all of it into memory. They're really too large and would swamp our server. We want to be able to somehow get a reference to the file and then use a proprietary, third-party API to ingest portions of it. We want to easily add, remove, and export files from storage. We'd like to set up automatic file replication between two servers (we can write a script for this.) That is, sync the contents of one server with another. We don't need a distributed system where it only appears as if we have one server. We'd like complete replication. We also have other smaller files that have a tree type relationship with the Big files. One file's content will point to the next and so on, and so on. It's not a "spoked wheel," it's a full blown tree. We'd prefer a Python, C or C++ API to work with a system like this but most of us are experienced with a variety of languages. We don't mind as long as it works, gets the job done, and saves us time. What you think? Is there something out there like this?

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  • What technology should I use to write my game?

    - by Alon
    I have a great idea for a 3D network game, and I've concluded that it is possible to write it in Java as an applet which will live under the web browser, just like a full software in C++. And it will look and feel the same. The main advantage of Java on C++ is that with Java you can play without downloading any software. I have already thought about the download of the graphics, sound, etc but I found a solution for it. RuneScape just proves that it is possible. So my first question is, should my game live on a web browser or on the operating system? I think that in a web browser it is much more portable, although you need install Java and stuff. But the fact is, that most MMO games are currently not in the web. If you suggest in a software so please suggest a language either - C++ or something more productive like Python or C#? So after choosing a language, I need a graphics solution. Should I write directly with OpenGL/DirectX or use a game engine? What game engine should I use? Ogre? jMonkeyEngine? What's your opinion? Thank you! P.S: Please don't use answers like "Use what you know".

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  • Django filters - Using an AllValuesFilter (with a LinkWidget) on a ManyToManyField

    - by magnetix
    This is my first Stack Overflow question, so please let me know if I do anything wrong. I wish to create an AllValues filter on a ManyToMany field using the wonderful django-filters application. Basically, I want to create a filter that looks like it does in the Admin, so I also want to use the LinkWidget too. Unfortunately, I get an error (Invalid field name: 'operator') if I try this the standard way: # Models class Organisation(models.Model): name = models.CharField() ... class Sign(models.Model): name = models.CharField() operator = models.ManyToManyField('Organisation', blank=True) ... # Filter class SignFilter(LinkOrderFilterSet): operator = django_filters.AllValuesFilter(widget=django_filters.widgets.LinkWidget) class Meta: model = Sign fields = ['operator'] I got around this by creating my own filter with the many to many relationship hard coded: # Models class Organisation(models.Model): name = models.CharField() ... class Sign(models.Model): name = models.CharField() operator = models.ManyToManyField('Organisation', blank=True) ... # Filter class MyFilter(django_filters.ChoiceFilter): @property def field(self): cd = {} for row in self.model.objects.all(): orgs = row.operator.select_related().values() for org in orgs: cd[org['id']] = org['name'] choices = zip(cd.keys(), cd.values()) list.sort(choices, key=lambda x:(x[1], x[0])) self.extra['choices'] = choices return super(AllValuesFilter, self).field class SignFilter(LinkOrderFilterSet): operator = MyFilter(widget=django_filters.widgets.LinkWidget) I am new to Python and Django. Can someone think of a more generic/elegant way of doing this?

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  • Updating entity fields in app engine development server

    - by Joey
    I recently tried updating a field in one of my entities on the app engine local dev server via the sdk console. It appeared to have updated just fine (a simple float). However, when I followed up with a query on the entity, I received an exception: "Items in the mSomeList list must all be Key instances". mSomeList is just another list field I have in that entity, not the one I modified. Is there any reason manually changing a field would adversely throw something off such that the server gets confused? Is this a known bug? I wrote an http handler to alter the field through server code and it works fine if I take that approach. Update: (adding details) I am using the python google app engine server. Basically if I go into the Google App Engine Launcher and press the SDK Console button, then go into one of my entities and edit a field that is a float (i.e. change it from 0 to 3.5, for instance), I get the "Items in the mMyList list must all be Key instance" suddenly when I query the entity like this: query = DataModels.RegionData.gql("WHERE mRegion = :1", region) entry = query.get() the RegionData entity is what has the mMyList member. As mentioned previously, if I do not manually change the field but rather do so through server code, i.e. query = DataModels.RegionData.gql("WHERE mRegion = :1", region) entry = query.get() entry.mMyFloat = 3.5 entry.put() Then it works.

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  • How do I connect to SQL Server with VB?

    - by Wayne Werner
    Hi, I'm trying to connect to a SQL server from VB. The SQL server is across the network uses my windows login for authentication. I can access the server using the following python code: import odbc conn = odbc.odbc('SignInspection') c = conn.cursor() c.execute("SELECT * FROM list_domain") c.fetchone() This code works fine, returning the first result of the SELECT. However, I've been trying to use the SqlClient.SqlConnection in VB, and it fails to connect. I've tried several different connection strings but this is the current code: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim conn As New SqlClient.SqlConnection conn.ConnectionString = "data source=signinspection;initial catalog=signinspection;integrated security=SSPI" Try conn.Open() MessageBox.Show("Sweet Success") 'Insert some code here, woo Catch ex As Exception MessageBox.Show("Failed to connect to data source.") MessageBox.Show(ex.ToString()) Finally conn.Close() End Try End Sub It fails miserably, and it gives me an error that says "A network-related or instance-specific error occurred... (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) I'm fairly certain it's my connection string, but nothing I've found has given me any solid examples (server=mySQLServer is not a solid example) of what I need to use. Thanks! -Wayne

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  • Initialize Static Array of Structs in C

    - by russell_h
    I implementing a card game in C. There are lots of types of cards and each has a bunch of information, including some actions that will need to be individually scripted associated with it. Given a struct like this (and I'm not certain I have the syntax right for the function pointer) struct CARD { int value; int cost; // This is a pointer to a function that carries out actions unique // to this card int (*do_actions) (struct GAME_STATE *state, int choice1, int choice2); }; I would like to initialize a static array of these, one for each card. I'm guessing this would look something like this int do_card0(struct GAME_STATE *state, int choice1, int choice2) { // Operate on state here } int do_card1(struct GAME_STATE *state, int choice1, int choice2) { // Operate on state here } extern static struct cardDefinitions[] = { {0, 1, do_card0}, {1, 3, do_card1} }; Will this work, and am I going about this the right way at all? I'm trying to avoid huge numbers of switch statements. Do I need to define the 'do_cardN' functions ahead of time, or is there some way to define them inline in the initialization of the struct (something like a lambda function in python)? I'll need read-only access to cardDefinitions from a different file - is 'extern static' correct for that? I know this is a lot of questions rolled into one but I'm really a bit vague about how to go about this. Thanks.

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  • Multiple use of a form before it is submitted

    - by OregonTrail
    I'm new to JavaScript, and trying to figure out the canonical way to do the following. I have a form with some checkboxes and a selector. Let's say the checkboxes are styles of music and the selector is for people's names. I'd like the user to be able to select the styles of music for each of the people's names and then submit the form with all of the data. For example, the user might first check off Classical, Jazz, Rock, and Pop and choose "Joe", then select Jazz, Pop, Country, and Electronica and choose "Jane". So there would have to be two different buttons for "submit person" and "submit form". I would like to: Have a list of the names and their chosen styles populate below the form, for feedback Allow the user to use the form as much as they want, and then submit all the data at the end I get the feeling that using jquery and JSON is perfect for this, but I'm not sure what search terminology to use to figure out how to do this. If it matters, the form will be processed by a Django view in Python.

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  • Summarising grouped records in a dataframe in R

    - by monch1962
    Hello all, I have a data frame in R that looks like this: > TimeOffset, Source, Length > 0 1 1500 > 0.1 1 1000 > 0.2 1 50 > 0.4 2 25 > 0.6 2 3 > 1.1 1 1500 > 1.4 1 18 > 1.6 2 2500 > 1.9 2 18 > 2.1 1 37 > ... and I want to convert it to > TimeOffset, Source, Length > 0.2 1 2550 > 0.6 2 28 > 1.4 1 1518 > 1.9 2 2518 > ... Trying to put this into English, I want to group consecutive records with the same 'Source' together, then printing out a single record per group showing the highest time offset in that group, the source, and the sum of the lengths in that group. The TimeOffset values will always increase. I suspect this is possible in R, but I really don't know where to start. In a pinch I could export the data frame out and do it in e.g. Python, but I'd prefer to stay within R if possible. Thanks in advance for any assistance you can provide

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  • Summarising grouped records in a dataframe in R (...again)

    - by monch1962
    Hello all, (I tried to ask this question earlier today, but later realised I over-simplified the question; the answers I received were correct, but I couldn't use them because of my over-simplification of the problem in the original question. Here's my 2nd attempt...) I have a data frame in R that looks like: "Timestamp", "Source", "Target", "Length", "Content" 0.1 , P1 , P2 , 5 , "ABCDE" 0.2 , P1 , P2 , 3 , "HIJ" 0.4 , P1 , P2 , 4 , "PQRS" 0.5 , P2 , P1 , 2 , "ZY" 0.9 , P2 , P1 , 4 , "SRQP" 1.1 , P1 , P2 , 1 , "B" 1.6 , P1 , P2 , 3 , "DEF" 2.0 , P2 , P1 , 3 , "IJK" ... and I want to convert this to: "StartTime", "EndTime", "Duration", "Source", "Target", "Length", "Content" 0.1 , 0.4 , 0.3 , P1 , P2 , 12 , "ABCDEHIJPQRS" 0.5 , 0.9 , 0.4 , P2 , P1 , 6 , "ZYSRQP" 1.1 , 1.6 , 0.5 , P1 , P2 , 4 , "BDEF" ... Trying to put this into English, I want to group consecutive records with the same 'Source' and 'Target' together, then print out a single record per group showing the StartTime, EndTime & Duration (=EndTime-StartTime) for that group, along with the sum of the Lengths for that group, and a concatenation of the Content (which will all be strings) in that group. The TimeOffset values will always increase throughout the data frame. I had a look at melt/recast and have a feeling that it could be used to solve the problem, but couldn't get my head around the documentation. I suspect it's possible to do this within R, but I really don't know where to start. In a pinch I could export the data frame out and do it in e.g. Python, but I'd prefer to stay within R if possible. Thanks in advance for any assistance you can provide

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  • How do you organise multiple git repositories?

    - by dbr
    With SVN, I had a single big repository I kept on a server, and checked-out on a few machines. This was a pretty good backup system, and allowed me easily work on any of the machines. I could checkout a specific project, commit and it updated the 'master' project, or I could checkout the entire thing. Now, I have a bunch of git repositories, for various projects, several of which are on github. I also have the SVN repository I mentioned, imported via the git-svn command.. Basically, I like having all my code (not just projects, but random snippets and scripts, some things like my CV, articles I've written, websites I've made and so on) in one big repository I can easily clone onto remote machines, or memory-sticks/harddrives as backup. The problem is, since it's a private repository, and git doesn't allow checking out of a specific folder (that I could push to github as a separate project, but have the changes appear in both the master-repo, and the sub-repos) I could use the git submodule system, but it doesn't act how I want it too (submodules are pointers to other repositories, and don't really contain the actual code, so it's useless for backup) Currently I have a folder of git-repos (for example, ~/code_projects/proj1/.git/ ~/code_projects/proj2/.git/), and after doing changes to proj1 I do git push github, then I copy the files into ~/Documents/code/python/projects/proj1/ and do a single commit (instead of the numerous ones in the individual repos). Then do git push backupdrive1, git push mymemorystick etc So, the question: How do your personal code and projects with git repositories, and keep them synced and backed-up?

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  • Packing an exe + dll into one executable (not .NET)

    - by Bluebird75
    Hi, Is anybody aware of a program that can pack several DLL and a .EXE into one executable. I am not talking about .NET case here, I am talking about general DLLs, some of which I generate in C++, some of others are external DLL I have no control over. My specific case is a python program packaged with py2exe, where I would like to "hide" the other DLL by packing them. The question is general enough though. The things that had a look at: ILMerge: specific to .NET NETZ: specific to .NET UPX: does DLL compression but not multiple DLL + EXE packing FileJoiner: Almost got it. It can pack executable + anything into one exe but when opened, it will launch the default opener for every file that was packed. So, if the user user dlldepend installed, it will launch it (becaues that's the default dll opener). Maybe that's not possible ? Summary of the answers: DLL opening is managed by the OS, so packing DLL into executable means that at some point, they need to be extracted to a place where the OS can find them. No magic bullet. So, what I want is not possible. Unless... We change something in the OS. Thanks Conrad for pointing me to ThinInstall, which virtualise the application and the OS loading mechanism. With ThinInstall, it is possible to pack everything in one exe (DLL, registry settings, ...).

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  • media.set_xx giving me grief!

    - by Firas
    New guy here. I asked a while back about a sprite recolouring program that I was having difficulty with and got some great responses. Basically, I tried to write a program that would recolour pixels of all the pictures in a given folder from one given colour to another. I believe I have it down, but, now the program is telling me that I have an invalid value specified for the red component of my colour. (ValueError: Invalid red value specified.), even though it's only being changed from 64 to 56. Any help on the matter would be appreciated! (Here's the code, in case I messed up somewhere else; It's in Python): import os import media import sys def recolour(old, new, folder): old_list = old.split(' ') new_list = new.split(' ') folder_location = os.path.join('C:\', 'Users', 'Owner', 'Spriting', folder) for filename in os.listdir (folder): current_file = media.load_picture(folder_location + '\\' + filename) for pix in current_file: if (media.get_red(pix) == int(old_list[0])) and \ (media.get_green(pix) == int(old_list[1])) and \ (media.get_blue(pix) == int(old_list[2])): media.set_red(pix, new_list[0]) media.set_green(pix, new_list[1]) media.set_blue(pix, new_list[2]) media.save(pic) if name == 'main': while 1: old = str(raw_input('Please insert the original RGB component, separated by a single space: ')) if old == 'quit': sys.exit(0) new = str(raw_input('Please insert the new RGB component, separated by a single space: ')) if new == 'quit': sys.exit(0) folder = str(raw_input('Please insert the name of the folder you wish to modify: ')) if folder == 'quit': sys.exit(0) else: recolour(old, new, folder)

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  • Google App Engine - How to implement the activity stream in a social network

    - by spidee
    I want some ideas on the best practice to implement an activity stream for a social network im building in app engine (PYTHON) I first want to keep a log for all activities of each user - so that we have a history. i.e. someone became a friend, added a picture, changed their address etc. This way we have a users history available should we need it. Also mean we can remove friendship joins, change user data but have a historical log. I also want to stream a users activity to their friends. for this only the last X activities need to be kept - that is in the scenario that messages are sent to friends when an activity occurs. Its pretty straight forward designing a history log - ie: when, what, where. The complication comes as to how we notify friends of a user as to their activity. In our app friendships are not mutual - ie they are based on the twitter following model. Some accounts could have thousands of followers. What is the best approach to model this. using a many to many join table and doing a costly query - using a feed class that fired a copy of the activity to all the subscribers - maybe into mcache? As their maybe a need to fire thousands of messages i would imagine a cron job would need to be used. Any help ideas thoughts on this Thx

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  • Java conditional compilation: how to prevent code chunks to be compiled?

    - by khachik
    My project requires Java 1.6 for compilation and running. Now I have a requirement to make it working with Java 1.5 (from the marketing side). I want to replace method body (return type and arguments remain the same) to make it compiling with Java 1.5 without errors. Details: I have an utility class called OS which encapsulates all OS-specific things. It has a method public static void openFile(java.io.File file) throws java.io.IOException { // open the file using java.awt.Desktop ... } to open files like with double-click (start Windows command or open Mac OS X command equivalent). Since it cannot be compiled with Java 1.5, I want to exclude it during compilation and replace by another method which calls run32dll for Windows or open for Mac OS X using Runtime.exec. Question: How can I do that? Can annotations help here? Note: I use ant, and I can make two java files OS4J5.java and OS4J6.java which will contain the OS class with the desired code for Java 1.5 and 1.6 and copy one of them to OS.java before compiling (or an ugly way - replace the content of OS.java conditionally depending on java version) but I don't want to do that, if there is another way. Elaborating more: in C I could use ifdef, ifndef, in Python there is no compilation and I could check a feature using hasattr or something else, in Common Lisp I could use #+feature. Is there something similar for Java? Found this post but it doesn't seem to be helpful. Any help is greatly appreciated. kh.

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  • Which templating languages output HTML *as a tree of nodes*?

    - by alamar
    HTML is a tree of nodes, before all. It's not just a text. However, most templating engines handle their input and output as it was just a text; they don't care what happens around their tags, their {$foo}'s and <% bar() %>'s; also they don't care about what are they outputting. Sometimes they happen to produce a correct html, but that's just a coincidence; they didn't aim for that, all they wanted is to replace some funny marks in the text stream with their evaluation. There are a few templating engines which do treat their output as a set of nodes; XSLT and Haml come to mind. For some tasks, this has advantages: for example, you can automatically reformat (like, delete all empty text nodes; auto-indent; word-wrap). The result is guaranteed to be a correct xml/sgml unless you use a strict subset of operations that can break that. Also, such templating engine would automatically quote strings, differently in text nodes and in attributes, because it strictly knows whether you're writing an attribute or a text node. Moreover, it can conditionally remove a node from output because it knows where it does begin and end, which is useful, and do other non-trivial node operations. You might not like XSLT for its verbosiness or functionalness, but it's damn helps that your template is xmllint-able XML, and your output is a good sgml/xml. So the question is: Which template engines do you know that treat their output as a set of correct nodes, not just an unstructured text? I know XSLT, Haml and some obscure python-based one. Moar!

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  • What are some of the core principles needed to master Multi threading using Delphi?

    - by Gary Becks
    I am kind of new to programming in general (about 8 months with on and off in delphi and a little python here and there) and I am in the process of buying some books. I am interested in learning about concurrent programming and building multi threaded apps using Delphi. Whenever I do a search for "multithreading delphi" or "delphi multithreading tutorial" I seem to get conflicting results as some of the stuff is about using certain libraries (omnithread library) and other stuff seems to be more geared towards programmers with more experience. I have studied quite a few books on delphi and for the most part they seem to kind of skim the surface and not really go into depth on the subject. I have a friend who is a programmer (he uses c++) who recommends I learn what is actually going on with the underlying system when using threads as opposed to jumping into how to actually implement them in my programs first. On amazon.com there are quite a few books on concurrent programming but none of them seem to be made with Delphi in mind. Basically I need to know what are the main things I should be focused on learning before jumping into using threads, if I can/should attempt to learn them using books that are not specifically aimed at delphi developers (don't want to confuse myself reading books with a bunch of code examples in other languages right now) and if there are any reliable resources/books on the subject that anyone here could recommend. Thanks in advance.

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  • Just 2 free months 2 learn or improve my skills

    - by microspino
    On the 30 of June I will leave my every day work to start as freelance developer. I'd like to set a period of 2 months apart to improve my dev skills. At work I code in C# and during my spare time I enjoyed building Ruby on Rails web applications and creating some Arduino prototypes. I'm something more than junior but I don't feel really a senior developer because I never had a big corporate project built and designed by me with help of other juniors (although I don't think this is really a good definiton of a "senior", It helps describing my feelings). Using a scale from 0 (ignorant) to 10 (proficient like a "samurai") the list below describes my skills that I would like to improve with just 2 months. I've already bought some nice and updated books on all the subjects hereunder: The order doesn't matter C = 1 C# & .Net = 6 Arduino & Processing = 2 Ruby = 5 Rails = 5 HTML/XHTML/CSS = 9 Javascript = 6 Objective-C/iPhone dev = 2 Python = 4 Django = 4 Desing Patterns = 3 Algorythms = 3 Git = 5 I haven't included SQL or Databases in general nor Networking because I spent 10 years working in the past with them and I feel pretty solid for now. As an aside, I've made up some interest in Redis, Node.js, HTML5 reading about them on the web. After two months, since I have to pay my bills, I could go searching for some new job. If learning and developing were really good maybe I could also invest on something I gave birth during them. Can You give me some piece of advice on which you think It's better to improve or develop a learning project on (something like a "summer of code" thing)? The all point Is to see my weeknesses and work on them.

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  • What kind of library to use for display of graphical objects and right click context menus

    - by Gopal
    Hi all, Goal: To develop a web based NMS interface which displays a network topology (e.g., switches, routers, links, endhosts). Each node should be 'movable' (draggable to an appropriate place manually or their best location computed algorithmically). I should be able to zoom into the network graph (say if there are many clusters of nodes and I want to concentrate on a particular cluster of nodes). I should be able to right-click any node or link and get a context menu (e.g., 'show routing table', 'show interfaces', 'show bandwidth utilization graph' etc.). The data for this network topology will be fetched by making calls to an apache based webserver where the backend scripts in python will fetch the appropriate data and send it via JSON to the web client. Question: I am assuming that some sort of javascript library/framework will be most appropriate for this - jQuery, Dojo, Moo etc. [I've never used any of these before]. Which of these would be most recommended for this sort of thing. Which would be easiest to learn (say in a months time). Thanks for any tips.

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  • Finding the width of a directed acyclic graph... with only the ability to find parents

    - by Platinum Azure
    Hi guys, I'm trying to find the width of a directed acyclic graph... as represented by an arbitrarily ordered list of nodes, without even an adjacency list. The graph/list is for a parallel GNU Make-like workflow manager that uses files as its criteria for execution order. Each node has a list of source files and target files. We have a hash table in place so that, given a file name, the node which produces it can be determined. In this way, we can figure out a node's parents by examining the nodes which generate each of its source files using this table. That is the ONLY ability I have at this point, without changing the code severely. The code has been in public use for a while, and the last thing we want to do is to change the structure significantly and have a bad release. And no, we don't have time to test rigorously (I am in an academic environment). Ideally we're hoping we can do this without doing anything more dangerous than adding fields to the node. I'll be posting a community-wiki answer outlining my current approach and its flaws. If anyone wants to edit that, or use it as a starting point, feel free. If there's anything I can do to clarify things, I can answer questions or post code if needed. Thanks! EDIT: For anyone who cares, this will be in C. Yes, I know my pseudocode is in some horribly botched Python look-alike. I'm sort of hoping the language doesn't really matter.

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  • execute a string of PHP code on the command line

    - by Matthew J Morrison
    I'd like to be able to run a line of PHP code on the command line similar to how the following options work: :~> perl -e "print 'hi';" :~> python -c "print 'hi'" :~> ruby -e "puts 'hi'" I'd like to be able to do: :~> php "echo 'hi';" I've read that there is a -r option that can do what I need for php, however it doesn't appear to be available when I try to use it. I've tried using PHP 5.2.13 and PHP 4.4.9 and neither have an -r option available. I wrote this script (that I called run_php.php) - which works, but I'm not a huge fan of it just because I feel like there should be a more "correct" way to do it. #!/usr/bin/php5 -q <?php echo eval($argv[1]); ?> My question is: is there a -r option? If so, why is it not available when I run --help? If there is no -r option, what is the best way to do this (without writing an intermediary script if possible)? Thanks!

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  • How to efficiently store and update binary data in Mongodb?

    - by Rocketman
    I am storing a large binary array within a document. I wish to continually add bytes to this array and sometimes change the value of existing bytes. I was looking for some $append_bytes and $replace_bytes type of modifiers but it appears that the best I can do is $push for arrays. It seems like this would be doable by performing seek-write type operations if I had access somehow to the underlying bson on disk, but it does not appear to me that there is anyway to do this in mongodb (and probably for good reason). If I were instead to just query this binary array, edit or add to it, and then update the document by rewriting the entire field, how costly will this be? Each binary array will be on the order of 1-2MB, and updates occur once every 5 minutes and across 1000s of documents. Worse, yet there is no easy way to spread these out (in time) and they will usually be happening close to one another on the 5 minute intervals. Does anyone have a good feel for how disastrous this will be? Seems like it would be problematic. An alternative would be to store this binary data as separate files on disk, implement a thread pool to efficiently manipulate the files on disk, and reference the filename from my mongodb document. (I'm using python and pymongo so I was looking at pytables). I'd prefer to avoid this though if possible. Is there any other alternative that I am overlooking here? Thanks in advnace.

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  • Does a Postgresql dump create sequences that start with - or after - the last key?

    - by bennylope
    I recently created a SQL dump of a database behind a Django project, and after cleaning the SQL up a little bit was able to restore the DB and all of the data. The problem was the sequences were all mucked up. I tried adding a new user and generated the Python error IntegrityError: duplicate key violates unique constraint. Naturally I figured my SQL dump didn't restart the sequence. But it did: DROP SEQUENCE "auth_user_id_seq" CASCADE; CREATE SEQUENCE "auth_user_id_seq" INCREMENT 1 START 446 MAXVALUE 9223372036854775807 MINVALUE 1 CACHE 1; ALTER TABLE "auth_user_id_seq" OWNER TO "db_user"; I figured out that a repeated attempt at creating a user (or any new row in any table with existing data and such a sequence) allowed for successful object/row creation. That solved the pressing problem. But given that the last user ID in that table was 446 - the same start value in the sequence creation above - it looks like Postgresql was simply trying to start creating rows with that key. Does the SQL dump provide the wrong start key by 1? Or should I invoke some other command to start sequences after the given start ID? Keenly curious.

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  • Java Function Analysis

    - by khan
    Okay..I am a total Python guy and have very rarely worked with Java and its methods. The condition is that I have a got a Java function that I have to explain to my instructor and I have got no clue about how to do so..so if one of you can read this properly, kindly help me out in breaking it down and explaining it. Also, i need to find out any flaw in its operation (i.e. usage of loops, etc.) if there is any. Finally, what is the difference between 'string' and 'string[]' types? public static void search(String findfrom, String[] thething){ if(thething.length > 5){ System.err.println("The thing is quite long"); } else{ int[] rescount = new int[thething.length]; for(int i = 0; i < thething.length; i++){ String[] characs = findfrom.split("[ \"\'\t\n\b\f\r]", 0); for(int j = 0; j < characs.length; j++){ if(characs[j].compareTo(thething[i]) == 0){ rescount[i]++; } } } for (int j = 0; j < thething.length; j++) { System.out.println(thething[j] + ": " + rescount[j]); } } }

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  • Rails original release source code

    - by user547057
    Hi, I've been looking to read some ruby code(specifically Rails) but I don't want to start with the current version of Rails since it has a lot of stuff I don't need and even more stuff that I wouldn't probably understand. I want to read only the core of Rails and supposedly the early versions were small and kind of easy to wrap one's head around(even for a neophyte like me). I have tried searching for the original release of rails, but have not been able to find it. The github repo consists of thousands of commits and I don't want to wade through those. What I want is to know whether there is any place I can get a zip or tar file with the original rails source or even the other early versions. Pointers to links will be very much appreciated. Thanks. p.s I'm new to ruby programming but not programming in general(I know a little python and scheme) and I understand blocks, lambdas and OO stuff, so I think I can tackle the rails source code. If anyone knows of other ruby projects that make for good code reading, i'd love to know of those too.

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  • Why do Scala maps have poor performance relative to Java?

    - by Mike Hanafey
    I am working on a Scala app that consumes large amounts of CPU time, so performance matters. The prototype of the system was written in Python, and performance was unacceptable. The application does a lot with inserting and manipulating data in maps. Rex Kerr's Thyme was used to look at the performance of updating and retrieving data from maps. Basically "n" random Ints were stored in maps, and retrieved from the maps, with the time relative to java.util.HashMap used as a reference. The full results for a range of "n" are here. Sample (n=100,000) performance relative to java, smaller is worse: Update Read Mutable 16.06% 76.51% Immutable 31.30% 20.68% I do not understand why the scala immutable map beats the scala mutable map in update performance. Using the sizeHint on the mutable map does not help (it appears to be ignored in the tested implementation, 2.10.3). Even more surprisingly the immutable read performance is worse than the mutable read performance, more significantly so with larger maps. The update performance of the scala mutable map is surprisingly bad, relative to both scala immutable and plain Java. What is the explanation?

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