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  • Are some data structures more suitable for functional programming than others?

    - by Rob Lachlan
    In Real World Haskell, there is a section titled "Life without arrays or hash tables" where the authors suggest that list and trees are preferred in functional programming, whereas an array or a hash table might be used instead in an imperative program. This makes sense, since it's much easier to reuse part of an (immutable) list or tree when creating a new one than to do so with an array. So my questions are: Are there really significantly different usage patterns for data structures between functional and imperative programming? If so, is this a problem? What if you really do need a hash table for some application? Do you simply swallow the extra expense incurred for modifications?

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  • Can zlib.crc32 or zlib.adler32 be safely used to mask primary keys in URLs?

    - by David Eyk
    In Django Design Patterns, the author recommends using zlib.crc32 to mask primary keys in URLs. After some quick testing, I noticed that crc32 produces negative integers about half the time, which seems undesirable for use in a URL. zlib.adler32 does not appear to produce negatives, but is described as "weaker" than CRC. Is this method (either CRC or Adler-32) safe for usage in a URL as an alternate to a primary key? (i.e. is it collision-safe?) Is the "weaker" Adler-32 a satisfactory alternative for this task? How the heck do you reverse this?! That is, how do you determine the original primary key from the checksum?

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  • Best practices for developing bigger applications on Android

    - by Janusz
    I've already written some small Android Applications, most of them in one Activity and nearly no data that should be persistent on the device. Now I'm writing an application that needs more Activities and I'm a bit puzzled about how to organize all this. My app will download some data parse it show it to the user and then show other activities depending on the data and the user interaction. Some of that data could be cached, some of it has to be downloaded every time. Some of that data should not be downloaded freshly at the moment the orientation changes, but it should on the moment the activity is created... Another thing I'm confused about are things like a httpClient. I now for example create a new httpclient for every activity, the same thing for locationlisteners. Are there books, a blogs or documentations with patterns, examples and advice on organizing larger apps build on android? Everything I found until now are get startet tutorials leaving me alone after 60 lines of code...

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  • Django/MySQL - __istartswith not producing case-insensitive query.

    - by TheLizardKing
    I make use of generic views and I am attempting to query my MySQL db (utf8_bin collation) in a case insensitive manor to try to find all my song titles that start with a particular letter. view.py def tracks_by_title(request, starts_with): return object_list( request, queryset = Track.objects.filter(title__istartswith=starts_with), template_name = 'tlkmusic_base/titles_list.html', template_object_name = 'tracks', paginate_by = 25, ) and my urls.py urlpatterns = patterns('tlkmusic.apps.tlkmusic_base.views', (r'^titles/(?P<starts_with>\w)/$', tracks_by_title), ) the query it produces according to the django debug toolbar is: SELECT `tracks`.`id`, `tracks`.`url`, `tracks`.`artist`, `tracks`.`album`, `tracks`.`genre`, `tracks`.`year`, `tracks`.`title`, `tracks`.`comment`, `tracks`.`tracknumber`, `tracks`.`discnumber`, `tracks`.`bitrate`, `tracks`.`length`, `tracks`.`samplerate`, `tracks`.`filesize`, `tracks`.`createdate`, `tracks`.`modifydate` FROM `tracks` WHERE `tracks`.`title` LIKE a% LIMIT 1 specifically this line: WHERE `tracks`.`title` LIKE a% LIMIT 1 Why is it not ILIKE which is what I was expecting by using __istartswith? I am using Django 1.1.1 on Ubuntu.

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  • django urls.py regex isn't working

    - by Phil
    This is for Django 1.2.5 and Python 2.7 on Wamp Server running apache version 2.2.17. My problem is that the my URLConf in urls.py isn't redirecting, it's just throwing a 404 error. urls.py: from django.conf.urls.defaults import * # Uncomment the next two lines to enable the admin: #from django.contrib import admin #admin.autodiscover() urlpatterns = patterns('', (r'^app/$', include('app.views.index')), # Uncomment the admin/doc line below to enable admin documentation: #(r'^admin/doc/', include('django.contrib.admindocs.urls')), # Uncomment the next line to enable the admin: #(r'^admin/', include(admin.site.urls)), ) views.py from django.http import HttpResponse def index(request): return HttpResponse("Hello World") I'm getting the following error: ImportError at /app/ No module named index I'm stumped as I'm only learning Django, can anybody see something wrong with my code? Here's my PythonPath: ['C:\Windows\system32\python27.zip', 'C:\Python27\Lib', 'C:\Python27\DLLs', 'C:\Python27\Lib\lib-tk', 'C:\wamp\bin\apache\Apache2.2.17', 'C:\wamp\bin\apache\apache2.2.17\bin', 'C:\Python27', 'C:\Python27\lib\site-packages', 'c:\wamp\www\seetwo']

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  • It is possible to call a servlet from a Java class?

    - by Renan Mozone
    I'm using IBM WebSphere as my servlet container. My application has several servlets and Java classes. My intent is to call one of those servlets directly from a Java class. Doing some research I figured out that is possible to use the RequestDispatcher interface to achieve this. But it is necessary to pass the objects ServletRequest and ServletResponse as arguments to the method forward(). There is some way to bypass this safely and "nicely"? By "nicely" I meant to say preserving good programming and design patterns.

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  • simpledateformat parsing date with 'Z' literal

    - by DanInDC
    I am trying to parse a date that looks like this: 2010-04-05T17:16:00Z This is a valid date per http://www.ietf.org/rfc/rfc3339.txt. The 'Z' literal "imply that UTC is the preferred reference point for the specified time." If I try to parse it using SimpleDateFormat and this pattern: yyyy-MM-dd'T'HH:mm:ss It will be parsed as a Mon Apr 05 17:16:00 EDT 2010 SimpleDateFormat is unable to parse the string with these patterns: yyyy-MM-dd'T'HH:mm:ssz yyyy-MM-dd'T'HH:mm:ssZ I can explicitly set the TimeZone to use on the SimpleDateFormat to get the expected output, but I don't think that should be necessary. Is there something I am missing? Is there an alternative date parser?

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  • Correct way to get absolute url in django

    - by dreamiurg
    A problem that I stumbled upon recently, and, even though I solved it, I would like to hear your opinion of what correct/simple/adopted solution would be. I'm developing website using Django + python. When I run it on local machine with "python manage.py runserver", local address is http://127.0.0.1:8000/ by default. However, on production server my app has other url, with path - like "http://server.name/myproj/" I need to generate and use permanent urls. If I'm using {% url view params %}, I'm getting paths that are relative to / , since my urls.py contains this urlpatterns = patterns('', (r'^(\d+)?$', 'myproj.myapp.views.index'), (r'^img/(.*)$', 'django.views.static.serve', {'document_root': settings.MEDIA_ROOT + '/img' }), (r'^css/(.*)$', 'django.views.static.serve', {'document_root': settings.MEDIA_ROOT + '/css' }), ) So far, I see 2 solutions: modify urls.py, include '/myproj/' in case of production run use request.build_absolute_uri() for creating link in views.py or pass some variable with 'hostname:port/path' in templates Are there prettier ways to deal with this problem? Thank you.

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  • Java Meta Search Engine API

    - by Loki
    I'm currently researching Java libraries to help in building a meta type search engine in the sense of being able to replace any given search engine in the back-end of the application or to simultaneously search using multiple search engines. I'm not interested in the GUI part here, just the generalization of search engine APIs and usage. I'd like to know about the common libraries used to achieve this task and if there are any common patterns used in this case. I imagined that this problem is common enough to be able to find plenty of stuff on Google, but it seems like search is a very proprietary domain and not much information is fed back to the community.

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  • Are there any widespread, modern Java coding conventions?

    - by brianegge
    Sun's "Code Conventions for the Java Programming Language" was last updated April 1999. Ten years later a lot has changed in the language, as well as general usage patterns. Are there more up to date, widely adopted standards? Most guidelines omit specifying file encoding and line endings. Sun recommends mixed tabs and spaces. The Eclipse IDE defaults to Eclipse's standard, which is tabs only. The Maven style guide is spaces only. Many style guides, such as JBoss, follow Sun's guidelines, but prefer K&R braces instead of OTBS. Each Apache project has it's own style guide, with slight differences between each one.

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  • How do I include full PartCover results with TeamCity 5?

    - by Jim Geurts
    Hi, I'm trying to get PartCover reports to generate correctly in TeamCity 5.0. When I click the Code Coverage tab in the build details, the reports are empty. I'm using the sln2008 build agent and my PartCoverage settings are as follows: Include Patterns: [*]* Report XSLT: C:\Program Files\PartCover .NET 2.3\xslt\Report By Assembly.xslt=>ByAssembly.html C:\Program Files\PartCover .NET 2.3\xslt\Report By Class.xslt=>ByClass.html Bonus points if you can describe how to include those reports (or just the important parts) with the email that TeamCity sends for successful/failed builds. I would like to continue using the sln2008 build agent, if possible, and not a different build agent.

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  • Which OOD approach should I take?

    - by Sorush Rabiee
    According to Niklaus Wirth, Algorithms + Data Structures = Programs. So I use this as a start point to object-oriented modeling and inheritance design: in a way that I separate the 'Objects' from 'Operations'. then look for patterns and inheritance hierarchy. But now after practice I guess it's not a good idea for every modeling problem, because sometimes it's not effective. (I mean there is no possibility of developing (or is very hard to develop) codes of Turing-Completed languages based on this paradigm.) What is your viewpoint for designing an OOD structure as an experienced programmer?

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  • url template tag in django template

    - by user192048
    guys: I was trying to use the url template tag in django, but no lucky, I defined my urls.py like this urlpatterns = patterns('', url(r'^analyse/$', views.home, name="home"), url(r'^analyse/index.html', views.index, name="index"), url(r'^analyse/setup.html', views.setup, name="setup"), url(r'^analyse/show.html', views.show, name="show"), url(r'^analyse/generate.html', views.generate, name="generate"), I defined the url pattern in my view like this {% url 'show'%} then I got this error message Caught an exception while rendering: Reverse for ''show'' with arguments '()' and keyword arguments '{}' not found. Original Traceback (most recent call last): File "/Library/Python/2.5/site-packages/django/template/debug.py", line 71, in render_node result = node.render(context) File "/Library/Python/2.5/site-packages/django/template/defaulttags.py", line 155, in render nodelist.append(node.render(context)) File "/Library/Python/2.5/site-packages/django/template/defaulttags.py", line 382, in render raise e NoReverseMatch: Reverse for ''show'' with arguments '()' and keyword arguments '{}' not found. I am wondering why django failed to render? what is the right way to define it in the tempalte?

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  • Ninject Given Path's format is not supported

    - by David Osborn
    The Ninject initialization works fine when i run my application directly from VS2010, but if I deploy the application to our custom "plugin" environment I get this error when I run the app and it tries to initialize Ninject. Error during initialization The given path's format is not supported. ERROR : The given path's format is not supported. Type : NotSupportedException Location: System.String CanonicalizePath(System.String, Boolean) Stack Trace: at System.Security.Util.StringExpressionSet.CanonicalizePath(String path, Boolean needFullPath) at System.Security.Util.StringExpressionSet.CreateListFromExpressions(String[] str, Boolean needFullPath) at System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, AccessControlActions control, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList) at System.Security.Permissions.FileIOPermission..ctor(FileIOPermissionAccess access, String[] pathList, Boolean checkForDuplicates, Boolean needFullPath) at System.IO.Path.GetFullPath(String path) at Ninject.Modules.ModuleLoader.NormalizePath(String path) at Ninject.Modules.ModuleLoader.GetFilesMatchingPattern(String pattern) at Ninject.Modules.ModuleLoader.b_0(String pattern) at System.Linq.Enumerable.d_142.MoveNext() at System.Linq.Lookup2.Create[TSource](IEnumerable1 source, Func2 keySelector, Func2 elementSelector, IEqualityComparer1 comparer) at System.Linq.GroupedEnumerable3.GetEnumerator() at Ninject.Modules.ModuleLoader.LoadModules(IEnumerable1 patterns) at Ninject.KernelBase.Load(IEnumerable`1 filePatterns) at Ninject.KernelBase..ctor(IComponentContainer components, INinjectSettings settings, INinjectModule[] modules) at Ninject.KernelBase..ctor(INinjectModule[] modules) at MyApp.Ioc.ResolveType.Initialize() at MyApp.Program.Run()

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  • How to implement a memory transaction scope in C#?

    - by theburningmonk
    Hi, we have a cache which I would like to put some transaction scopes around so that any process have to explicitly 'commit' the changes it wants to do to the cached objects and make it possible to rollback any changes when the process fails halfway as well. Right now, we're deep cloning the cached objects on get requests, it works but it's not a clean solution and involves a fair bit of maintenance too. I remember hearing about some MTS (memory transaction scope) solution on .NetRocks a while back but can't remember the name of it! Does anyone know of a good MTS framework out there? Alternatively, if I was to implement my own, are there any good guidelines/patterns on how to do this? Thanks,

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  • Asp.Net MVC style routing in Django

    - by Andrew Hanson
    I've been programming in Asp.Net MVC for quite some time now and to expand a little bit beyond the .Net world I've recently began learning Python and Django. I am enjoying Django but one thing I am missing from Asp.Net MVC is the automatic routing from my urls to my controller actions. In Asp.Net MVC I can build much of my application using this single default route: routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = "" } // Parameter defaults ); In Django I've found myself adding an entry to urls.py for each view that I want to expose which leads to a lot more url patterns than I've become used to in Asp.Net MVC. Is there a way to create a single url pattern in Django that will handle "[Application]/view/[params]" in a way similar to Asp.Net MVC? Perhaps at the main web site level?

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  • get a list of function names in a shell script

    - by n-alexander
    I have a Bourne Shell script that has several functions in it, and allows to be called in the following way: my.sh <func_name> <param1> <param2> Inside func_name() will be called with param1 and param2. I want to create a "help" function that would just list all available functions, even without parameters. The question: how do I get a list of all function names in a script from inside the script? I'd like to avoid having to parse it and look for function patterns. Too easy to get wrong. Thanks, Alex

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  • Practices for Foreground/Background threads in .NET

    - by Andrei Taptunov
    I work with in-house legacy communication framework which exposes some high level abstractions. These abstractions are wrappers with some logic around .NET threads. When I looked at code I've noticed that some abstractions are wrappers around foreground threads while others are wrappers around background threads. The sad thing is that I don't see any logic why in some cases foreground threads are used and background in other cases. Are there any guidelines or patterns & practices when it's better to choose one over another on server side and client side (I believe there should be some difference)?

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  • Methods for ensuring security between users in multi-user applications

    - by Emilio
    I'm writing a multiuser application (.NET - C#) in which each user's data is separated from the others and there is no data that's common between users. It's critical to ensure that no user has access to another user's data. What are some approaches for implementing security at the database level and/or in the application architecture to to accomplish this? For example (and this is totally made up - I'm not suggesting it's a good or bad approach) including a userID column in all data tables might be an approach. I'm developing the app in C# (asp.net) and SQL Server 2008. I'm looking for options that are are either native in the tools I'm using or general patterns.

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  • Silverlight 3-4 reference kind (e-)book.

    - by Bubba88
    Hello! I'm looking for a source of information about Microsoft Silverlight to begin practically efficient programming custom functionality applications. I want to pretend just for now that I don't need any ideologically correct refresher (SL tips, top patterns, VS tutorials :) and etc.). Basically, what I want is a reference kind e-book, where I could find any practically relevant info outlined in a minimalistic manner. If you do remember something fitting the above description, I ask you to give me a hint. Thank you very much!

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  • How to program asynchronous Windows Forms Applications?

    - by Nestor
    I'm writting a Windows Forms application in C# that performs a lot of long-running procedures. I need to program the application so that the GUI doesn't lock. What is the best way to program it? I know how to use the following: BeginInvoke/EndInvoke Calling Application.DoEvents() repeatedly (probably not a good idea) BackgroundWorker etc. But how to manage GUI state with call backs, etc... is not trivial. Are there solutions for this (in the form of patterns or libraries)?

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  • How to add texture to fill colors in ggplot2?

    - by rhh
    I'm currently using scale_brewer for fill and these look beautiful in color (on screen and via color printer) but print relatively uniformly as greys when using a black and white printer. I searched the online ggplot2 documentation but didn't see anything about adding textures to fill colors. Is there an official ggplot2 way to do this or does anyone have a hack that they use? By textures I mean things like diagonal bars, reverse diagonal bars, dot patterns, etc that would differentiate fill colors when printed in black and white. Thanks for thoughts! Robert

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  • What do you do to keep current

    - by griegs
    I've noticed that as I progress in my career I my day to day activities require less and less actual hands on development. However, I feel that I need to stay current, both for my own personal desire as well as being able to guide a team to best practices etc. I'm finding it very hard to stay on top of the game because there are so many new frameworks, technologies and patterns coming out. Do I concentrate on a particular aspect or framework? Do I become a generalist or a specialist? What are others doing to maintain a certain level of proficiency and currentness (sic)?

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  • Find what unknown function does in C using gdb

    - by Gary
    Hi, I have a function m(int i, char c) which takes and returns a char between "-abc...xyz" and also takes an integer i. Basically I have no way to see the source code of the function but can call it and get the return value. Using gdb/C, what's the best way to decipher what the function actually does? I've tried looking for patterns using consecutive chars and integer inputs but have come up with nothing yet. If it helps, here are some results of testing the return values, with the first two bits being the arguments and the last bit being the return value: 0 a i 0 b l 0 c t 0 d x 0 e f 0 f v 1 a q 1 b i 1 c y 1 d e 2 a a 2 b y 2 c f 2 d n

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