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  • Why is Python used for high-performance/scientific computing (but Ruby isn't)?

    - by Cyclops
    There's a quote from a PyCon 2011 talk that goes: At least in our shop (Argonne National Laboratory) we have three accepted languages for scientific computing. In this order they are C/C++, Fortran in all its dialects, and Python. You’ll notice the absolute and total lack of Ruby, Perl, Java. It was in the more general context of high-performance computing. Granted the quote is only from one shop, but another question about languages for HPC, also lists Python as one to learn (and not Ruby). Now, I can understand C/C++ and Fortran being used in that problem-space (and Perl/Java not being used). But I'm surprised that there would be a major difference in Python and Ruby use for HPC, given that they are fairly similar. (Note - I'm a fan of Python, but have nothing against Ruby). Is there some specific reason why the one language took off? Is it about the libraries available? Some specific language features? The community? Or maybe just historical contigency, and it could have gone the other way?

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  • i18n and L10n (1)

    - by Aaron Li
    Internationalization (i18n) is a way of designing and developing a software product to function in multiple locales. This process involves identifying the locales that must be supported, designing features which support those locales, and writing code that functions equally well in any of the supported locales. Localization (L10n) is a process of modifying or adapting a software product to fit the requirements of a particular locale. This process includes (but may not be limited to) translating the user interface, documentation and packaging, changing dialog box geometries, customizing features (if necessary), and testing the translated product to ensure that it still works (at least as well as the original). i18n is a pre-requisite for L10n. Resource is 1. any part of a program which can appear to the user or be changed or configured by the user. 2. any piece of the program's data, as opposed to its code. Core product is the language independent portion of a software product (as distinct from any particular localized version of that product - including the English language version). Sometimes, however, this term is used to refer to the English product as opposed to other localizations.   Useful links http://www.mozilla.org/docs/refList/i18n/ http://www.w3.org/International/ http://hub.opensolaris.org/bin/view/Community+Group+int_localization/

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  • Do you think we will ever settle on a "standard" platform? [closed]

    - by GazTheDestroyer
    The recent explosion of phone platforms has depressed me (slightly), and made me wonder if we will ever reach any kind of standard for presentation? I don't mean language or IDE. Different languages have different strengths and I can see that there may always be a need for disparity, although I do note that languages are merging somewhat in functionality, with traditional imperitive languages like C++ now supporting things like lambdas. What I'm really talking about is a common presentation mechanism. Before smart phones and tablets came along, the web seemed to be finally becoming a reasonable platform for presenting an application that was globally accessible, not just geographically, but by platform too. Sure there are still (sometimes infuriating) implementation differences and quirks, but if you wrote a decent site you knew it could be accessed on anything from a PC to a phone to a C64 running the right software. "Write Once Run Anywhere" seemed to finally be becoming a reality. However, in the last few years we've seen an explosion of mobile operating systems, and the ubiquitous "app". A good site is no longer enough, you need a native "app", and of course we have a sudden massive disparity in OS, language, and APIs needed to write them as each battles for supremecy. It's kind of weird how the cycle of popularity goes. Mainframes with terminals - thin client. PC - thick client. Web browser - thin client. Phone app - thick(ish) client. I just wonder if you think there will ever be a global standard for clients, or whether the "shiny and different" cycle will always continue along with the battle of the tech du jour.

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  • what should I read in Windows [closed]

    - by Umesha MS
    I think I am asking generic question. Being a developer in windows what should I read to improve my skills? Do I need to read concepts on need basis or do I need to read concepts well in advance? If I want to read the concepts in advance then what topics do I need to read. (Note : I am a Windows developer. I use c++ programming language, Win32/MFC frame work and I use Visual studio IDE.) Updated: To be more specific when a fresher comes to my team I will ask him to read the following things and I tell him that these are very important. 1)C++ : 1 The C++ Programming Language by Bjarne Stroustrup's 2 Thinking in C++ 2nd Edition by Bruce Eckel 2)Win32/MFC : 1 Programming Applications for Microsoft Windows by Jeffrey Richter 2 windows programming by charles petzold 3 Programming Windows with MFC –by Jeff Prosise For 2 years and above developer I ask them to read 1)Above concepts (C++ and Win32/MFC)are mandate 2)Design Pattern : 1)Gang Of Four. 2)Head first patter. 3)Design princples. But for above 6 years’ experience developer what are the concepts are important.

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  • Location-Based redirection and duplication in sub-directories affecting SEO

    - by Joshua
    I currently own the website www.xyz.com. The website has a sub-directory for each of the 3 target countries: .../en-US/ (United States), .../es-MX/ (Mexico), and .../es-DO/ (Dominican Republic). I have two main questions about this setup: Currently, the main domain/root (xyz.com) contains a blank index.php file, but I would like for a user to be redirected to one of the sub-directories based on their regional location. What is the best way to accomplish this? I have looked at using browser language-based redirection, but how would I know whether to direct a user to the MX or DO site if the browser language is set to spanish? Is there a way to detect a user's geographic location? Also, the 3 websites are practically identical except they all have 3 unique color schemes and the US site is in english while the MX and DO sites are in spanish. My problem is that I believe GoogleBot is penalizing/banning my site because the spanish text on the MX and DO pages are nearly identical and are thus marked as duplicates/spam. Is there a way to avoid this?

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  • What helped YOU learn C++? [on hold]

    - by Tips48
    So here's my attempt to not get this question closed for too subjective :P I'm a young programmer, specifically interested in Game Development. I've written my first couple games in Java, which I would consider my self intermediate-Advanced in. As I start to prepare myself for college and (hopefully) internships, I've noticed that learning C/C++ is essential to the industry. I've decided to start with C++, and so I read a couple of books that I saw were suggested. Anyway, now I have a decent understanding of the basics, but I really want to enhance my language knowledge. Instead of just asking for things to do, I was wondering what were some exercises that you did that really helped you understand the language? Preferably they would be near the beginner level. I understand that they obviously won't be directly related to Game Development, but it be nice if there were some things that I could transfer over eventually. (Specifically, I struggle with memory (pointers, etc) since there is no such concept in Java) Thanks! - Tips P.S.: Here's to hoping this isn't to subjective :P

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  • Why does Scala require functions to have explicit return type?

    - by garbage collection
    I recently began learning to program in Scala, and it's been fun so far. I really like the ability to declare functions within another function which just seems to intuitive thing to do. One pet peeve I have about Scala is the fact that Scala requires explicit return type in its functions. And I feel like this hinders on expressiveness of the language. Also it's just difficult to program with that requirement. Maybe it's because I come from Javascript and Ruby comfort zone. But for a language like Scala which will have tons of connected functions in an application, I cannot conceive how I brainstorm in my head exactly what type the particular function I am writing should return with recursions after recursions. This requirement of explicit return type declaration on functions, do not bother me for languages like Java and C++. Recursions in Java and C++, when they did happen, often were dealt with 2 to 3 functions max. Never several functions chained up together like Scala. So I guess I'm wondering if there is a good reason why Scala should have the requirement of functions having explicit return type?

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  • Bikeshedding: Placeholders in strings

    - by dotancohen
    I find that I sometimes use placeholders in strings, like this: $ cat example-apache <VirtualHost *:80> ServerName ##DOMAIN_NAME## ServerAlias www.##DOMAIN_NAME## DocumentRoot /var/www/##DOMAIN_NAME##/public_html </VirtualHost> Now I am sure that it is a minor issue if the placeholder is ##DOMAIN_NAME##, !!DOMAIN_NAME!!, {{DOMAIN_NAME}}, or some other variant. However, I now need to standardize with other developers on a project, and we all have a vested interest in having our own placeholder format made standard in the organization. Are there any good reasons for choosing any of these, or others? I am trying to quantify these considerations: Aesthetics and usability. For example, __dict__ may be hard to read as we don't know how many underscores are in there. Compatibility. Will some language try to do something funny with {} syntax in a string (such as PHP does with "Welcome to {$siteName} today!")? Actually, I know that PHP and Python won't, but others? Will a C++ preprocessor choke on ## format? If I need to store the value in some SQL engine, will it not consider something a comment? Any other pitfalls to be wary of? Maintainability. Will the new guy mistake ##SOME_PLACEHOLDER## as a language construct? The unknown. Surely the wise folk here will think of other aspects of this decision that I have not thought of. I might be bikeshedding this, but if there are real issues that might be lurking then I would certainly like to know about them before mandating that our developers adhere to a potentially-problematic convention.

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  • Which topics do I need to research to enable me to complete my self-assigned "Learning Project"?

    - by Anonymous -
    I want to continue learning C#. I've read parts of a few books recommended on here and the language is feeling more familiar by the day. I'd like to tackle a mid-sized personal project to take my expertise to the next level. What I'd like to do, is create an application that 'manages expenses', that runs on multiple machines on a LAN. So for example, say we have person1 and person2 on seperate machines running the application, when person1 enters an expense, it will appear on person2's (pretty UI) view of the expenses database and vice versa. What topics do I need to research to make this possible for me? I plan on learning WPF for the UI (though the steep learning curve (or so I'm told) has me a little anxious about that at this stage. With regards to the database, which database would you recommend I use? I don't want a 'server' for the database to run on, so do I need to use an embedded database that each client machine runs a copy of that updates to each other (upon startup/entering of expense on any machine etc)? What topics under networking should I be looking at? I haven't studied networking before in any language, so do I need to learn about sockets or?

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  • Placeholders in strings

    - by dotancohen
    I find that I sometimes use placeholders in strings, like this: $ cat example-apache <VirtualHost *:80> ServerName ##DOMAIN_NAME## ServerAlias www.##DOMAIN_NAME## DocumentRoot /var/www/##DOMAIN_NAME##/public_html </VirtualHost> Now I am sure that it is a minor issue if the placeholder is ##DOMAIN_NAME##, !!DOMAIN_NAME!!, {{DOMAIN_NAME}}, or some other variant. However, I now need to standardize with other developers on a project, and we all have a vested interest in having our own placeholder format made standard in the organization. Are there any good reasons for choosing any of these, or others? I am trying to quantify these considerations: Aesthetics and usability. For example, __dict__ may be hard to read as we don't know how many underscores are in there. Compatibility. Will some language try to do something funny with {} syntax in a string (such as PHP does with "Welcome to {$siteName} today!")? Actually, I know that PHP and Python won't, but others? Will a C++ preprocessor choke on ## format? If I need to store the value in some SQL engine, will it not consider something a comment? Any other pitfalls to be wary of? Maintainability. Will the new guy mistake ##SOME_PLACEHOLDER## as a language construct? The unknown. Surely the wise folk here will think of other aspects of this decision that I have not thought of. I might be bikeshedding this, but if there are real issues that might be lurking then I would certainly like to know about them before mandating that our developers adhere to a potentially-problematic convention.

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  • Good quality Secure Software Development Training [closed]

    - by Patrick
    Just had my annual appraisal and found out my company is willing to pay for training and exams etc! Woohoo (they kept that one quiet). I'm interested in doing a course on secure development techniques. Has anyone got any suggestions for good quality distance learning courses in secure development (I could probably get a couple of days off to attend a conference/ course if required)? We're mostly an MS .Net house but I have no particular allegiance to MS or any other programming language (though, obviously, C++ is the best language in the world). I have 12 years development experience working in (what are now) PCI:DSS environments, including designing and developing a key management system and I have some knowledge of basic attacks (XSS, injection etc). I would prefer a hard course I struggle with to a basic course I learn 3 things from (but hopefully get something right at my level). A quick google found these two course which look good: http://www.sans.org/course/secure-coding-net-developing-defensible-applications https://www.isc2.org/csslpedu/default.aspx I don't really know how to choose between them, and finding other courses isn't going to make that job any easier, so I thought I'd ask those who know. EDIT : Hmm, care to share the reason for your down vote, will help me learn how to use the site better...

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  • Selectively Including files in C#.net web application [migrated]

    - by segnosaur
    I am attempting to modify an application with the following characteristics: Written in C#.net Using Visual Studio 2010 The application uses a Master sheet to maintain commonality The Master sheet has the following: <%@ Master Language="C#" AutoEventWireup="true" CodeFile="mysheet.master.cs" Inherits="master_mysheet" %> Now, currently, the master sheet has an include file that brings in a common footer: #include file="inc/my-footer.inc" Here's what I want to do: I would like to modify the master sheet to be able to read in a footer based on the value contained in a session variable... i.e. (not real code, but just something to give an idea of what I want) if session("x") = "a" then #include file="inc/my-footer1.inc" else #include file="inc/my-footer2.inc" My first instinct was to go with some vbscript: <script type="text/vbscript" language="vbscript"> document.write("vbscript example.") </script> However, it doesn't run the vbscript code automatically on page load. Does anyone know: - The syntax I need to actually get this to work? i.e. to get the vbscript to run automatically on page load, AND to do the page include? - Or, is there a better way to go about this? (perhaps by doing some coding in C#) Note: I am experienced in C#; however, I haven't done any vbscript since the days of ASP classic, so my knowledge there is out of date.

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  • I am having a hard time learning Python, is it just me? [closed]

    - by Carpet
    For the past two weeks I am trying to learn Python and a framework for web development, while doing so I learned a lot but not what I was looking for. I did manage to get everything set up and running, followed tutorials, but I still have not managed to create a navigation bar and a simple template website. My goal is to create web applications (like a blog) and perhaps platforms similar to stackoverflow. In which language was stackoverflow created in? I believe that Python Django or Python Tornado (which I tried) is more for people who have learned desktop application development. It is hard for me to make sense out of the complex and fragmented system. I'm able to develop with PHP and have already created blogs and similar applications. If Python and a framework is not for me, what type of language would be for me, which languages are used for these type of platforms, I would like to develop myself? I only omitted PHP because I found it later on a bit too inheriting, and the code is hardly readable and becomes quickly cluttered, I love how readable Python code is.

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  • Oracle ADF Mobile

    - by rituchhibber
    We are happy to announce that Oracle ADF Mobile is now available for our customers.Oracle ADF Mobile enables developer to build applications that install and run on both iOS and Android devices from one source code.Development is done with JDeveloper and ADF and leverages Java and HTML5 technologies, while keeping the same visual and declarative approach ADF is known for.Please Click here to read more about the Oracle ADF Mobile release and learn more on our OTN Page. Feature Highlights: Java - Oracle brings a Java VM embedded with each application so you can develop all your business logic in the platform neutral language you know and love! (Yes, even iOS!) JDBC - Since we give you Java, we also provide JDBC along with a SQLite driver and engine that also supports encryption out of the box. Multi-Platform - Truly develop your application only once and deploy to multiple platforms. iOS and Android platforms are supported for both phone and tablet. Flexible - You can decide how to implement the UI: Use existing server-based UI framework like JSF. Use your own favorite HTML5 framework like JQuery. Use our declarative HTML5 component set provided with the framework. Device Feature Access - You can get access to device features from either Java or JavaScript to invoke features like camera, GPS, email, SMS, contacts, etc. Secure - ADF Mobile provides integrated security that works with your server back-end as well. Whether you’re using remote URLs, local HTML or AMX, you can secure any/all of your features with a single consistent login page. Since we also give you SQLite encryption, we are assured that your data is safe. Rapid - Using the same development techniques that ADF developers are already used to, you can quickly create mobile applications without ever learning another language!ADF Mobile XML or AMX for short, provides all the normal input and layout controls you expect and we also add charts/maps/gauges along with it to provide a very comprehensive UI controls. You can also mix and match any of the three for ultimate flexibility!

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  • Web Host which provides Latex and embedded programming [duplicate]

    - by Polymer
    This question already has an answer here: How to find web hosting that meets my requirements? 5 answers Hopefully this is a reasonable place to ask this question. I'll confess I'm a little green when it comes to web programming and websites in general (though not programming). I'm a Math and Physics person. I want to make a personal webpage containing a Math and Physics blog. Ideally the blog should support latex, and embedded programs. This would allow me to write, say, an equation for an orbit and then show what the orbit would look like (perhaps letting the reader configure parameters). The programming language can be javascript (though it isn't my favorite language). My budget is around 5 dollars a month. Does anybody have suggestions for a good Shared host with these kind of requirements? And a small aside, It would be useful if I can move the website content, since I might live at a university in the nearish future. They would have servers which could support such a webpage.

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  • Have suggestions for these assembly mnemonics?

    - by Noctis Skytower
    Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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  • Are there any suggestions for these new assembly mnemonics?

    - by Noctis Skytower
    Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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  • PHP: Writing non-english characters to XML - encoding problem

    - by Dean
    Hello, I wrote a small PHP script to edit the site news XML file. I used DOM to manipulate the XML (Loading, writing, editing). It works fine when writing English characters, but when non-English characters are written, PHP throws an error when trying to load the file. If I manually type non-English characters into the file - it's loaded perfectly fine, but if PHP writes the non-English characters the encoding goes wrong, although I specified the utf-8 encoding. Any help is appreciated. Errors: Warning: DOMDocument::load() [domdocument.load]: Entity 'times' not defined in filepath Warning: DOMDocument::load() [domdocument.load]: Input is not proper UTF-8, indicate encoding ! Bytes: 0x91 0x26 0x74 0x69 in filepath Here are the functions responsible for loading and saving the file (self-explanatory): function get_tags_from_xml(){ // Load news entries from XML file for display $errors = Array(); if(!$xml_file = load_news_file()){ // Load file // String indicates error presence $errors = "file not found"; return $errors; } $taglist = $xml_file->getElementsByTagName("text"); return $taglist; } function set_news_lang(){ // Sets the news language global $news_lang; if($_POST["news-lang"]){ $news_lang = htmlentities($_POST["news-lang"]); } elseif($_GET["news-lang"]){ $news_lang = htmlentities($_GET["news-lang"]); } else{ $news_lang = "he"; } } function load_news_file(){ // Load XML news file for proccessing, depending on language global $news_lang; $doc = new DOMDocument('1.0','utf-8'); // Create new XML document $doc->load("news_{$news_lang}.xml"); // Load news file by language $doc->formatOutput = true; // Nicely format the file return $doc; } function save_news_file($doc){ // Save XML news file, depending on language global $news_lang; $doc->saveXML($doc->documentElement); $doc->save("news_{$news_lang}.xml"); } Here is the code for writing to XML (add news): <?php ob_start()?> <?php include("include/xml_functions.php")?> <?php include("../include/functions.php")?> <?php get_lang();?> <?php //TODO: ADD USER AUTHENTICATION! if(isset($_POST["news"]) && isset($_POST["news-lang"])){ set_news_lang(); $news = htmlentities($_POST["news"]); $xml_doc = load_news_file(); $news_list = $xml_doc->getElementsByTagName("text"); // Get all existing news from file $doc_root_element = $xml_doc->getElementsByTagName("news")->item(0); // Get the root element of the new XML document $new_news_entry = $xml_doc->createElement("text",$news); // Create the submited news entry $doc_root_element->appendChild($new_news_entry); // Append submited news entry $xml_doc->appendChild($doc_root_element); save_news_file($xml_doc); header("Location: /cpanel/index.php?lang={$lang}&news-lang={$news_lang}"); } else{ header("Location: /cpanel/index.php?lang={$lang}&news-lang={$news_lang}"); } ?> <?php ob_end_flush()?>

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  • What does the `forall` keyword in Haskell/GHC do?

    - by JUST MY correct OPINION
    I've been banging my head on this one for (quite literally) years now. I'm beginning to kinda/sorta understand how the foreach keyword is used in so-called "existential types" like this: data ShowBox = forall s. Show s => SB s (This despite the confusingly-worded explanations of it in the fragments found all around the web.) This is only a subset, however, of how foreach is used and I simply cannot wrap my mind around its use in things like this: runST :: forall a. (forall s. ST s a) -> a Or explaining why these are different: foo :: (forall a. a -> a) -> (Char,Bool) bar :: forall a. ((a -> a) -> (Char, Bool)) Or the whole RankNTypes stuff that breaks my brain when "explained" in a way that makes me want to do that Samuel L. Jackson thing from Pulp Fiction. (Don't follow that link if you're easily offended by strong language.) The problem, really, is that I'm a dullard. I can't fathom the chicken scratchings (some call them "formulae") of the elite mathematicians that created this language seeing as my university years are over two decades behind me and I never actually had to put what I learnt into use in practice. I also tend to prefer clear, jargon-free English rather than the kinds of language which are normal in academic environments. Most of the explanations I attempt to read on this (the ones I can find through search engines) have these problems: They're incomplete. They explain one part of the use of this keyword (like "existential types") which makes me feel happy until I read code that uses it in a completely different way (like runST, foo and bar above). They're densely packed with assumptions that I've read the latest in whatever branch of discrete math, category theory or abstract algebra is popular this week. (If I never read the words "consult the paper whatever for details of implementation" again, it will be too soon.) They're written in ways that frequently turn even simple concepts into tortuously twisted and fractured grammar and semantics. (I suspect that the last two items are the biggest problem. I wouldn't know, though, since I'm too much a dullard to comprehend them.) It's been asked why Haskell never really caught on in industry. I suspect, in my own humble, unintelligent way, that my experience in figuring out one stupid little keyword -- a keyword that is increasingly ubiquitous in the libraries being written these days -- are also part of the answer to that question. It's hard for a language to catch on when even its individual keywords cause years-long quests to comprehend. Years-long quests which end in failure. So... On to the actual question. Can anybody completely explain the foreach keyword in clear, plain English (or, if it exists somewhere, point to such a clear explanation which I've missed) that doesn't assume I'm a mathematician steeped in the jargon?

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  • How to write a bison grammer for WDI?

    - by Rizo
    I need some help in bison grammar construction. From my another question: I'm trying to make a meta-language for writing markup code (such as xml and html) wich can be directly embedded into C/C++ code. Here is a simple sample written in this language, I call it WDI (Web Development Interface): /* * Simple wdi/html sample source code */ #include <mySite> string name = "myName"; string toCapital(string str); html { head { title { mySiteTitle; } link(rel="stylesheet", href="style.css"); } body(id="default") { // Page content wrapper div(id="wrapper", class="some_class") { h1 { "Hello, " + toCapital(name) + "!"; } // Lists post ul(id="post_list") { for(post in posts) { li { a(href=post.getID()) { post.tilte; } } } } } } } Basically it is a C source with a user-friendly interface for html. As you can see the traditional tag-based style is substituted by C-like, with blocks delimited by curly braces. I need to build an interpreter to translate this code to html and posteriorly insert it into C, so that it can be compiled. The C part stays intact. Inside the wdi source it is not necessary to use prints, every return statement will be used for output (in printf function). The program's output will be clean html code. So, for example a heading 1 tag would be transformed like this: h1 { "Hello, " + toCapital(name) + "!"; } // would become: printf("<h1>Hello, %s!</h1>", toCapital(name)); My main goal is to create an interpreter to translate wdi source to html like this: tag(attributes) {content} = <tag attributes>content</tag> Secondly, html code returned by the interpreter has to be inserted into C code with printfs. Variables and functions that occur inside wdi should also be sorted in order to use them as printf parameters (the case of toCapital(name) in sample source). Here are my flex/bison files: id [a-zA-Z_]([a-zA-Z0-9_])* number [0-9]+ string \".*\" %% {id} { yylval.string = strdup(yytext); return(ID); } {number} { yylval.number = atoi(yytext); return(NUMBER); } {string} { yylval.string = strdup(yytext); return(STRING); } "(" { return(LPAREN); } ")" { return(RPAREN); } "{" { return(LBRACE); } "}" { return(RBRACE); } "=" { return(ASSIGN); } "," { return(COMMA); } ";" { return(SEMICOLON); } \n|\r|\f { /* ignore EOL */ } [ \t]+ { /* ignore whitespace */ } . { /* return(CCODE); Find C source */ } %% %start wdi %token LPAREN RPAREN LBRACE RBRACE ASSIGN COMMA SEMICOLON CCODE QUOTE %union { int number; char *string; } %token <string> ID STRING %token <number> NUMBER %% wdi : /* empty */ | blocks ; blocks : block | blocks block ; block : head SEMICOLON | head body ; head : ID | ID attributes ; attributes : LPAREN RPAREN | LPAREN attribute_list RPAREN ; attribute_list : attribute | attribute COMMA attribute_list ; attribute : key ASSIGN value ; key : ID {$$=$1} ; value : STRING {$$=$1} /*| NUMBER*/ /*| CCODE*/ ; body : LBRACE content RBRACE ; content : /* */ | blocks | STRING SEMICOLON | NUMBER SEMICOLON | CCODE ; %% I am having difficulties on defining a proper grammar for the language, specially in splitting WDI and C code . I just started learning language processing techniques so I need some orientation. Could someone correct my code or give some examples of what is the right way to solve this problem?

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  • Do you have suggestions for these assembly mnemonics?

    - by Noctis Skytower
    Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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  • nil object in view when building objects on two different associations

    - by Shako
    Hello all. I'm relatively new to Ruby on Rails so please don't mind my newbie level! I have following models: class Paintingdescription < ActiveRecord::Base belongs_to :paintings belongs_to :languages end class Paintingtitle < ActiveRecord::Base belongs_to :paintings belongs_to :languages end class Painting < ActiveRecord::Base has_many :paintingtitles, :dependent => :destroy has_many :paintingdescriptions, :dependent => :destroy has_many :languages, :through => :paintingdescriptions has_many :languages, :through => :paintingtitles end class Language < ActiveRecord::Base has_many :paintingtitles, :dependent => :nullify has_many :paintingdescriptions, :dependent => :nullify has_many :paintings, :through => :paintingtitles has_many :paintings, :through => :paintingdescriptions end In my painting new/edit view, I would like to show the painting details, together with its title and description in each of the languages, so I can store the translation of those field. In order to build the languagetitle and languagedescription records for my painting and each of the languages, I wrote following code in the new method of my Paintings_controller.rb: @temp_languages = @languages @languages.size.times{@painting.paintingtitles.build} @painting.paintingtitles.each do |paintingtitle| paintingtitle.language_id = @temp_languages[0].id @temp_languages.slice!(0) end @temp_languages = @languages @languages.size.times{@painting.paintingdescriptions.build} @painting.paintingdescriptions.each do |paintingdescription| paintingdescription.language_id = @temp_languages[0].id @temp_languages.slice!(0) end In form partial which I call in the new/edit view, I have <% form_for @painting, :html => { :multipart => true} do |f| %> ... <% languages.each do |language| %> <p> <%= label language, language.name %> <% paintingtitle = @painting.paintingtitles[counter] %> <% new_or_existing = paintingtitle.new_record? ? 'new' : 'new' %> <% prefix = "painting[#{new_or_existing}_title_attributes][]" %> <% fields_for prefix, paintingtitle do |paintingtitle_form| %> <%= paintingtitle_form.hidden_field :language_id%> <%= f.label :title %><br /> <%= paintingtitle_form.text_field :title%> <% end %> <% paintingdescription = @painting.paintingdescriptions[counter] %> <% new_or_existing = paintingdescription.new_record? ? 'new' : 'new' %> <% prefix = "painting[#{new_or_existing}_title_attributes][]" %> <% fields_for prefix, paintingdescription do |paintingdescription_form| %> <%= paintingdescription_form.hidden_field :language_id%> <%= f.label :description %><br /> <%= paintingdescription_form.text_field :description %> <% end %> </p> <% counter += 1 %> <% end %> ... <% end %> But, when running the code, ruby encounters a nil object when evaluating paintingdescription.new_record?: You have a nil object when you didn't expect it! You might have expected an instance of ActiveRecord::Base. The error occurred while evaluating nil.new_record? However, if I change the order in which I a) build the paintingtitles and painting descriptions in the paintings_controller new method and b) show the paintingtitles and painting descriptions in the form partial then I get the nil on the paintingtitles.new_record? call. I always get the nil for the objects I build in second place. The ones I build first aren't nil in my view. Is it possible that I cannot build objects for 2 different associations at the same time? Or am I missing something else? Thanks in advance!

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  • Diophantine Equation [closed]

    - by ANIL
    In mathematics, a Diophantine equation (named for Diophantus of Alexandria, a third century Greek mathematician) is a polynomial equation where the variables can only take on integer values. Although you may not realize it, you have seen Diophantine equations before: one of the most famous Diophantine equations is: X^n+Y^n=Z^n We are not certain that McDonald's knows about Diophantine equations (actually we doubt that they do), but they use them! McDonald's sells Chicken McNuggets in packages of 6, 9 or 20 McNuggets. Thus, it is possible, for example, to buy exactly 15 McNuggets (with one package of 6 and a second package of 9), but it is not possible to buy exactly 16 nuggets, since no non- negative integer combination of 6's, 9's and 20's adds up to 16. To determine if it is possible to buy exactly n McNuggets, one has to solve a Diophantine equation: find non-negative integer values of a, b, and c, such that 6a + 9b + 20c = n. Problem 1 Show that it is possible to buy exactly 50, 51, 52, 53, 54, and 55 McNuggets, by finding solutions to the Diophantine equation. You can solve this in your head, using paper and pencil, or writing a program. However you chose to solve this problem, list the combinations of 6, 9 and 20 packs of McNuggets you need to buy in order to get each of the exact amounts. Given that it is possible to buy sets of 50, 51, 52, 53, 54 or 55 McNuggets by combinations of 6, 9 and 20 packs, show that it is possible to buy 56, 57,..., 65 McNuggets. In other words, show how, given solutions for 50-55, one can derive solutions for 56-65. Problem 2 Write an iterative program that finds the largest number of McNuggets that cannot be bought in exact quantity. Your program should print the answer in the following format (where the correct number is provided in place of n): "Largest number of McNuggets that cannot be bought in exact quantity: n" Hints: Hypothesize possible instances of numbers of McNuggets that cannot be purchased exactly, starting with 1 For each possible instance, called n, a. Test if there exists non-negative integers a, b, and c, such that 6a+9b+20c = n. (This can be done by looking at all feasible combinations of a, b, and c) b. If not, n cannot be bought in exact quantity, save n When you have found six consecutive values of n that in fact pass the test of having an exact solution, the last answer that was saved (not the last value of n that had a solution) is the correct answer, since you know by the theorem that any amount larger can also be bought in exact quantity

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  • Query Results Not Expected

    - by E-Madd
    I've been a CF developer for 15 years and I've never run into anything this strange or frustrating. I've pulled my hair out for hours, googled, abstracted, simplified, prayed and done it all in reverse. Can you help me? A cffunction takes one string argument and from that string I build an array of "phrases" to run a query with, attempting to match a location name in my database. For example, the string "the republic of boulder" would produce the array: ["the","republic","of","boulder","the republic","the republic of","the republic of boulder","republic of","republic of boulder","of boulder"]. Another cffunction uses the aforementioned cffunction and runs a cfquery. A query based on the previously given example would be... select locationid, locationname, locationaliasname from vwLocationsWithAlias where LocationName in ('the','the republic','the republic of','republic','republic of','republic of boulder','of','of boulder','boulder') or LocationAliasName in ('the','the republic','the republic of','republic','republic of','republic of boulder','of','of boulder','boulder') This returns 2 records... locationid - locationname - locationalias 99 - 'Boulder' - 'the republic' 68 - 'Boulder' - NULL This is good. Works fine and dandy. HOWEVER... if the string is changed to "the republic", resulting in the phrases array ["the","republic","the republic"] which is then used to produce the query... select locationid, locationname, locationaliasname from vwLocationsWithAlias where LocationName in ('the','the republic','republic') or LocationAliasName in ('the','the republic','republic') This returns 0 records. Say what?! OK, just to make sure I'm not involuntarily HIGH I run that very same query in my SQL console against the same database in the cf datasource. 1 RECORD! locationid - locationname - locationalias 99 - 'Boulder' - 'the republic' I can even hard-code that sql within the same cffunction and get that one result, but never from the dynamically generated SQL. I can get my location phrases from another cffunction of a different name that returns hard-coded array values and those work, but never if the array is dynamically built. I've tried removing cfqueryparams, triple-checking my datatypes, datasource setups, etc., etc., etc. NO DICE WTF!? Is this an obscure bug? Am I losing my mind? I've tried everything I can think of and others (including Ray Camden) can think of. ColdFusion 8 (with all the latest hotfixes) SQL Server 2005 (with all the greatest service packs) Windows 2003 Server (with all the latest updates, service packs and nightly MS voodoo)

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