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  • Type patterns and generic classes in Haskell

    - by finnsson
    I'm trying to understand type patterns and generic classes in Haskell but can't seem to get it. Could someone explain it in laymen's terms? In [1] I've read that "To apply functions generically to all data types, we view data types in a uniform manner: except for basic predefined types such as Float, IO, and ?, every Haskell data type can be viewed as a labeled sum of possibly labeled products." and then Unit, :*: and :+: are mentioned. Are all data types in Haskell automatically versions of the above mentioned and if so how do I figure out how a specific data type is represented in terms of :*:, etc? The users guide for generic classes (ch. 7.16) at haskell.org doesn't mention the predefined types but shouldn't they be handled in every function if the type patterns should be exhaustive? [1] Comparing Approaches to Generic Programming in Haskell, Ralf Hinze, Johan Jeuring, and Andres Löh

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  • Good way to cache data during Android application lifecycle?

    - by sniurkst
    Hello, keeping my question short, I have creating application with 3 activities, where A - list of categories, B - list of items, C - single item. Data displayed in B and C is parsed from online XML. But, if I go trough A - B1 - C, then back to A and then back to B1 I would like to have it's data cached somewhere so I wouldn't have to request XML again. I'm new to Android and Java programming, I've googled a lot and still can't find (or simply do not have an idea where to look) a way to do what I want. Would storing all received data in main activity A (HashMaps? ContentProviders?) and then passing to B and C (if they get same request that was before) be a good idea?

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  • performance monitoring tools for multi-tenant web application

    - by Anton
    We have a need to monitor performance of our java web app. We are looking for some tolls which can help us with this task. The major difficulty is that we are SaaS provider with multi-tenant server architecture with hundreds of customers running on the same hardware. So far we tried commercial products like DynaTrace and Coradinat but unfortunately they don't get the job done so far. What we need is a simple report which would tell us if we had performance problems on each customer site in a specified period of time. Mostly it will be response time per customer but also we will need some more specifics based on the URLs. please let me know if someone had any experience with setting up such monitoring. Thanks!

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  • What to know - for building a form with PHP and MySQL

    - by Tal Galili
    Hello all, I have three weeks to perform the following basic task. I wish to create an online form in PHP that will get 5 numbers and with them: save the numbers to a MySQL DB do a simple computation on the numbers and return them as an output to the visitor I already have a domain, hosting and a MySQL database+user. I don't know PHP, or SQL or databases. I do have prior knowledge in C and R (which means I have some of the basics of programming, and I am not intimidated of a new languages). My question are: Am I missing something? is there some other skill I should have for this task that I don't know of? What is a good way to learn the skills needed for the task I described? Hope the question isn't too basic/general. Thanks!

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  • Why the "mutable default argument fix" syntax is so ugly, asks python newbie

    - by Cawas
    Now following my series of "python newbie questions" and based on another question. Go to http://python.net/~goodger/projects/pycon/2007/idiomatic/handout.html#other-languages-have-variables and scroll down to "Default Parameter Values". There you can find the following: def bad_append(new_item, a_list=[]): a_list.append(new_item) return a_list def good_append(new_item, a_list=None): if a_list is None: a_list = [] a_list.append(new_item) return a_list So, question here is: why is the "good" syntax over a known issue ugly like that in a programming language that promotes "elegant syntax" and "easy-to-use"? Why not just something in the definition itself, that the "argument" name is attached to a "localized" mutable object like: def better_append(new_item, a_list=[].local): a_list.append(new_item) return a_list I'm sure there would be a better way to do this syntax, but I'm also almost positive there's a good reason to why it hasn't been done. So, anyone happens to know why?

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  • Dealing with Anti-Microsoft Trolls on The Internet

    - by FlySwat
    I'm an active member on Programming Reddit, but I'm one of the few C# advocates there. I could write up a 3 paragraph explanation of how to do something there, just to have it voted into the negatives because I used C# as an example. As a developer using the "Microsoft Stack", how do you handle the trolls and bigots in the online world? These are the kind of people who say things like "M$", or that Vista sucks without ever booting up. Do you just ignore the trolls?

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  • Resources for TDD aimed at Python Web Development

    - by Null Route
    I am a hacker not and not a full-time programmer but am looking to start my own full application development experiment. I apologize if I am missing something easy here. I am looking for recommendations for books, articles, sites, etc for learning more about test driven development specifically compatible with or aimed at Python web application programming. I understand that Python has built-in tools to assist. What would be the best way to learn about these outside of RTFM? I have searched on StackOverflow and found the Kent Beck's and David Astels book on the subject. I have also bookmarked the Wikipedia article as it has many of these types of resources. Are there any particular ones you would recommend for this language/application?

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  • Best way to check for null values in Java?

    - by Arty-fishL
    I need to check whether the function of an object returns true or false in Java, but that object may be null, so obviously then the function would throw a NullPointerException. This means I need to check if the object is null before checking the value of the function. What is the best way to go about this? I've listed some methods I considered, I just want to know the most sensible one, the one that is best programming practice for Java (opinion?). // method 1 if (foo != null) { if (foo.bar()) { etc... } } // method 2 if (foo != null ? foo.bar() : false) { etc... } // method 3 try { if (foo.bar()) { etc... } } catch (NullPointerException e) { } // method 4 // would this work all the time, would it still call foo.bar()? if (foo != null && foo.bar()) { etc... }

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  • Is there any advantages to integrate Smarty with Zend?

    - by keisimone
    Hi, i am quite familiar with Smarty and recently decided to use Zend framework in implementation. because i am aware of the various advantages of Smarty, i insisted my contractor to integrate Smarty in. But now, i am questioning my assumptions. Should I integrate Smarty in with Zend framework? simply because I am familiar with Smarty syntax? I am also involved with the programming. I got the contractor to help in the architecture and with the prototype.

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  • printing uid of a file on linux system

    - by neo730
    i am learning c programming. I am trying to make my own program similar to ls command but with less options.what i am doing is taking input directory/file name as argument and then gets all directory entry with dirent struct(if it is directory) . After it i use stat() to take all information of the file but here is my problem when i use write() to print these value its fine but when i want to print these with printf() i get warninng : format ‘%ld’ expects type ‘long int’, but argument 2 has type ‘__uid_t’. I don't know what should use at place of %ld and also for other special data types.

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  • How stable or unstable is symfony 2.0 ?

    - by Doron
    Well, I know it's a preview, and I know it says that it's not yet ready for production, and yet I dare ask the question. I need to start building a pretty big application, which is planned to go live at around sep-oct 2010. Lets say I will not release the application to production until the stable version of symfony 2.0 will be released - is it a good idea (well, I'll settle for a viable idea) for me to start building the application using the 2.0 version ? How big is the chance I will need to rewrite/replace code I've written due to core changes in the framework ? Thanks. Edit: the other option right now, is to use symfony 1.4. I have thought and tried Zend Framework, but I refuse to re-invent each and every module, which will cost me a lot of programming hours (if not days/weeks).

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  • A compiler for automata theory

    - by saadtaame
    I'm designing a programming language for automata theory. My goal is to allow programmers to use machines (DFA, NFA, etc...) as units in expressions. I'm confused whether the language should be compiled, interpreted, or jit-compiled! My intuition is that compilation is a good choice, for some operations might take too much time (converting NFA's to equivalent DFA's can be expensive). Translating to x86 seems good. There is one issue however: I want the user to be able to plot machines. Any ideas?

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  • Why can't I install psycopg2? (Python 2.6.4, PostgreSQL 8.4, OS X 10.6)

    - by cojadate
    After running python setup.py install I get the following: Warning: Unable to find 'pg_config' filebuilding 'psycopg2._psycopg' extension gcc-4.0 -arch ppc -arch i386 -fno-strict-aliasing -fno-common -dynamic -DNDEBUG -g -O3 - DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.2.1 (dt dec ext pq3)" -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -DHAVE_PQPROTOCOL3=1 -I/Library/Frameworks/Python.framework/Versions/2.6/include/python2.6 -I. -c psycopg/psycopgmodule.c -o build/temp.macosx-10.3-fat-2.6/psycopg/psycopgmodule.o unable to execute gcc-4.0: No such file or directory error: command 'gcc-4.0' failed with exit status 1 There's probably something screamingly obvious there to anyone who knows the first thing about back-end web programming, but unfortunately it's all gobbledegook to me. The psycopg2 documentation was not helpful.

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  • Should I start a General Software Developer User Group? [closed]

    - by Jeb
    I'm moving to a small town (Panama City, Florida) at some point in the future. I've found a Linux user group, and a .Net user group, but I'd like to spend my time outside of the office learning about Python, Android, JQuery -- mostly things that aren't owned by .Net. I'm debating trying to start another user group of some sort there, primarily to attract programmers who use technologies other than .Net. What are some of the more general programming user groups in existence already? I'm looking for something I could franchise.

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  • Best way to return a user-generated file, AJAX or Forms?

    - by Bill Zimmerman
    Hi, I'm new to web programming, so I need some help. I am writing a custom file-creation app for my site. A user visits the page, clicks on some various options and toggles some checkboxes, and the presses a 'download now' link. I have a PHP backend which will be processing the submission, and generating a PDF file. After the user presses the download link, I want the download to start like it would for any static link. My question is: What is the best way to do this? From my limited understanding, I have a choice between using AJAX or somehow using forms to submit the data. What are the advantages/disadvantages of each? Does anyone have any good links to examples? Thanks

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  • Parallel Assignment operator in Ruby

    - by Bragaadeesh
    Hi, I was going through an example from Programming in Ruby book. This is that example def fib_up_to(max) i1, i2 = 1, 1 # parallel assignment (i1 = 1 and i2 = 1) while i1 <= max yield i1 i1, i2 = i2, i1+i2 end end fib_up_to(100) {|f| print f, " " } The above program simply prints the fibonacci numbers upto 100. Thats fine. My question here is when i replace the parallel assignment with something like this, i1 = i2 i2 = i1+i2 I am not getting the desired output. My question here is, is it advisable to use parallel assignments? (I come from Java background and it feels really wierd to see this type of assignment) One more doubt is : Is parallel assignment an operator?? Thanks

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  • How to get distinct values from a column with all its corresponding values in another column

    - by Vishnu
    I know the question is bit confusing. Please read below. I have a table table_categories (id INT(11), cname VARCHAR(25),survey_id INT(11)) I want to retrieve the values for the column cname without duplication, that is distinct values but with all the values in the other column. id cname survey_id -- -------- --------- 1 Trader 2 2 Beginner 2 25 Human 1 26 Human 2 From the above example I want to retrieve distinct cnames with all the values of the survey_id. I don't want to use any programming language. Is there any way by using a single query. Please give me a solution in MySQL.

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  • Consolidate loan, purchase & sale tables into one transaction table.

    - by Frank Computer
    INFORMIX-SE with ISQL 7.3: I have separate tables for Loan, Purchase & Sales transactions. Each tables rows are joined to their respective customer rows by: customer.id [serial] = loan.foreign_id [integer]; = purchase.foreign_id [integer]; = sale.foreign_id [integer]; I would like to consolidate the three tables into one table called "transaction", where a column: transaction.trx_type char(1) {L=Loan, P=Purchase, S=Sale} identifies the transaction type. Each transaction will be assigned a unique transaction number [serial]. Is this a good idea or is it better to keep them in separate tables? Storage space is not a concern, I think it would be easier programming & user-wise to have all types of transactions under one table, whenever possible. This implies denormalization.

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  • COM port - how to identify a device (.net/c#)

    - by argh
    Hi, I'm programming for Windows CE and I need to connect to a scanner. There is no problem - I know that it is on port COM0, but if I plug in another device earlier it gets another COM port... to get all com ports the easy way is: SerialPort.GetPortNames() But I don't know how to identify a device? Is there any standard way? I can't 'ping' it since there is one device that only sends data... it spams data all the time... and I don't know how to 'ping' a device...

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  • Zend framework helper intellisense

    - by Nicky De Maeyer
    Not so much a programming problem, but more a productivity problem. We've got quite a few custom view and action helpers in our project. Working with around 7 programmers. Now when someone, creates a helper or if one would want to use a helper, it all goes through the brokers. This means we do not get intellisense for those helpers, which can be real time consuming, having to go look in the docs or the code files. This is ofcourse true for both build in and custom helpers. Does any1 share this pain? Does any1 have a solution for this?

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  • Redirect print in Python: val = print(arg) to output mixed iterable to file

    - by emcee
    So lets say I have an incredibly nested iterable of lists/dictionaries. I would like to print them to a file as easily as possible. Why can't I just redirect print to a file? val = print(arg) gets a SyntaxError. Is there a way to access stdinput? And why does print take forever with massive strings? Bad programming on my side for outputting massive strings, but quick debugging--and isn't that leveraging the strength of an interactive prompt? There's probably also an easier way than my gripe. Has the hive-mind an answer?

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  • Essential Training Topics for Supervisors of ASP.NET Developers

    - by Dave Johnson
    I have a co-worker who supervises a group of ASP.NET developers who are doing lots of ASP.NET/SQL Server apps. My co-worker was very technical at one time, but his last programming assignment was writing Fortran code in the 1980s. He has asked me to help him gain a deeper knowledge of ASP.NET Web application development to equip him in his supervisory role. I will be spending an hour every other week with him providing training, and he will probably not have a lot of time to commit otherwise. What would you recommend as topics to cover, tutorial resources, etc. so that I can help him get up to speed in his role as a supervisor of ASP.NET developers?

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  • seting ODBC Datasource in IBM AIX server

    - by adisembiring
    Hi ..... I have develop IBM Message broker flow database application in windows xp environment. the database accessed using ODBC datasource. basically, I use compute node with esql programming to select query in database, and I set the datasource in the compute node properties. Now want to deployed my project to AIX server. but, I dont know how to set ODBC datasource in AIX server. can you help me to how to set odbc in AIX server, can you help me to solve my problem ?? Thanks

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  • Surely there is a better grid than DataGrid for the .NET Compact Framework...

    - by PavelR
    Having spent a couple of days wrestling with DataGrid in .NET CF, especially controlling the look and feel, I'm looking for alternatives. I don't mind purchasing a solution. I'm looking for Redistributable to our enterprise customers. We control the hardware so it doesn't have to work perfectly on every device. Display strings and numbers in columns with headings. Scrollable, but no paging. Don't row editing. Need to add and delete rows. User re-sizable column widths, and a way to persist that. Work with .NET CF 2.0 or 3.5 on Windows CE 6.0 Any suggestions on grids or toolkits?

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  • need suggestions about content filtering project

    - by serdar
    i'm thinking of designing and implementing a content filtering software as my graduation project. i want it to be a user contributed software. i mean, users can also add/categorize websites. it should be also a web project and extensions for browsers like chrome, firefox, ie.. my question is which programming language do you suggest for this project? i know that firefox extensions are javascript based maybe you can say use .net framework 3.5 because it's better in communication with extensions. sorry for my bad english.. btw any other suggessions about project will be good.. thx a lot.

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