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  • Interpreted languages: The higher-level the faster?

    - by immersion
    I have designed around 5 experimental languages and interpreters for them so far, for education, as a hobby and for fun. One thing I noticed: The assembly-like language featuring only subroutines and conditional jumps as structures was much slower than the high-level language featuring if, while and so on. I developed them both simultaneously and both were interpreted languages. I wrote the interpreters in C++ and I tried to optimize the code-execution part to be as fast as possible. My hypothesis: In almost all cases, performance of interpreted languages rises with their level (high/low). Am I basically right with this? (If not, why?)

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  • How do programming languages bind identifiers to functions

    - by sub
    I'm talking about C and/or C++ here as this are the only languages I know used for interpreters where the following could be a problem: If we have an interpreted language X how can a library written for it add functions to the language which can then be called from within programs written in the language? PHP example: substr( $str, 5, 10 ); How is the function substr added to the "function pool" of PHP so it can be called from within scripts? It is easy for PHP storing all registered function names in an array and searching through it as a function is called in a script. However, as there obviously is no eval in C(++), how can the function then be called? I assume PHP doesn't have 100MB of code like: if( identifier == "substr" ) { return PHP_SUBSTR(...); } else if( ... ) { ... } Ha ha, that would be pretty funny. I hope you have understood my question so far. How do interpreters solve this problem? How can I solve this for my own experimental toy interpreter?

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  • Restarting or stopping apache results in waiting forever

    - by steko
    I have two simple WSGI apps running on top of mod_wsgi and apache2 on a test development server. There is no mod_python on this machine. The WSGI configuration is as follows WSGIDaemonProcess tops stack-size=524288 maximum-requests=5 WSGIScriptAlias /tops /home/ubuntu/tops-cloud/tops.wsgi <Directory /home/ubuntu/tops-cloud> WSGIProcessGroup tops WSGIApplicationGroup %{GLOBAL} Order deny,allow Allow from all </Directory> WSGIDaemonProcess flaskal maximum-requests=5 WSGIScriptAlias /c14 /home/ubuntu/c14/flaskal/flaskal.wsgi <Directory /home/ubuntu/c14/flaskal> WSGIProcessGroup flaskal WSGIApplicationGroup %{GLOBAL} Order deny,allow Allow from all </Directory> If I make changes to the app, I need to restart the web server, so I would expect that a simple sudo service apache2 restart does what I need. Same goes for any changes to the config (e.g. number of maximum requests, etc). Instead, it never ends "waiting", like this: $ sudo service apache2 restart * Restarting web server apache2 ... waiting .................................................. until I just do CTRL-C. At that point, the only way to resume a working server is to kill the process and restart it, not very convenient. The same happens with the stop command. The error logs at the "debug" level show the following lines after a failed restart [Wed Nov 14 21:55:19 2012] [notice] caught SIGTERM, shutting down [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=9047): Shutdown requested 'tops'. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=9047): Stopping process 'tops'. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=9047): Destroying interpreters. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=9047): Cleanup interpreter ''. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=9047): Terminating Python. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=8920): Shutdown requested 'flaskal'. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=8920): Stopping process 'flaskal'. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=8920): Destroying interpreters. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=8920): Cleanup interpreter ''. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=8920): Terminating Python. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=8920): Python has shutdown. [Wed Nov 14 21:55:19 2012] [info] mod_wsgi (pid=9047): Python has shutdown. If I then try to restart again (with the process still running), I get the following error: * Restarting web server apache2 (98)Address already in use: make_sock: could not bind to address 0.0.0.0:80 no listening sockets available, shutting down Unable to open logs Action 'start' failed. The Apache error log may have more information. Unfortunately the Apache error log doesn't have anything. When apache2 is running properly, both apps work without any problem.

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  • Learning to implement dynamically typed language compiler

    - by TriArc
    I'm interested in learning how to create a compiler for a dynamically typed language. Most compiler books, college courses and articles/tutorials I've come across are specifically for statically typed languages. I've thought of a few ways to do it, but I'd like to know how it's usually done. I know type inferencing is a pretty common strategy, but what about others? Where can I find out more about how to create a dynamically typed language? Edit 1: I meant dynamically typed. Sorry about the confusion. I've written toy compilers for statically typed languages and written some interpreters for dynamically typed languages. Now, I'm interested in learning more about creating compilers for a dynamically typed language. I'm specifically experimenting with LLVM and since I need to specify the type of every method and argument, I'm thinking of ways to implement a dynamically typed language on something like LLVM.

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  • What is the equivalent word for "compile" in an interpreted language?

    - by user46874
    (I was encouraged to ask this question here.) In C, we say: GCC compiles foo.c. For interpreters (such as Lua), what is the equivalent verb? The Lua interpreter ____ foo.lua. When I write instructions for users of my Lua script, I often say: Run the interpreter on foo.lua. I think this can be said more succinctly: Interpret (or Translate) foo.lua. but that sounds awkward for some reason (perhaps because I'm unsure of its correctness). I can't really say compile because users may confuse it with the usage of the Lua compiler when I actually mean the Lua interpreter.

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  • What platform is best for Android and iPhone development?

    - by Toy Yoda
    I've been developing non-mobile apps for linux; mainly stuff like interpreters, compilers, database engines and business apps. I've been told that if I wanted to learn how to develop iPhone/iPad applications, I should buy a Mac since Apple has all it's development tools for iPhone/iPad on Mac. Now, what about Android phones / tablets? Are the development tools better on Mac or PC? I need to buy a new laptop, and I would like to factor in mobile development in my choice of PC or Mac.

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  • How fast should an interpreted language be today?

    - by Tarbal
    Is speed of the (main/only viable) implementation of an interpreted programming language a criteria today? What would be the optimal balance between speed and abstraction? Should scripting languages completely ignore all thoughts about performance and just follow the concepts of rapid development, readability, etc.? I'm asking this because I'm currently designing some experimental languages and interpreters

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  • Applocker custom extension (Java, CPL, MSC etc.)

    - by test1839
    We have a Terminal server and want to prevent users from running inappropriate software. Previously we used Software Restriction Policies for this purpose. Now, Microsoft seems to recommend Applocker instead. However we found no possibilities to add custom extensions like JAR, CPL, MSC etc. which was possible in Software Restriction Policies. Do you know how to add custom extensions to the Applocker policies in Windows 2008? Or how can we block custom script interpreters like Perl etc.?

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  • I run a command twice - I'm wondering if it'll be a problem

    - by Delirium tremens
    "In computing, tee is a command in various command-line interpreters (shells) such as Unix shells, 4DOS/4NT and Windows PowerShell, which displays or pipes the output of a command and copies it into a file or a variable. It is primarily used in conjunction with pipes and filters." I run echo FRAMEBUFFER=y | sudo tee /etc/initramfs-tools/conf.d/splash twice. I opened the conf.d folder in Nautilus, but there isn't a splash file nor directory. I expected a file to be there with FRAMEBUFFER=y inside but there isn't. Is this going to be a problem?

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  • Intercept Apache communication

    - by Nathan Adams
    I am looking to develop a solution that eliminates potential spammers. The way this system will work is that it will watch connections and requests. Going into the specifics is more for stackoverflow, But, what I am interested in is if it is possible to tell Apache to pass the request over to my application first and give it the ability to accept/deny the request. Sure, it will make requests slower, but I think that is a trade off I am willing to take. I still want, however, Apache to run the request through any interpreters (such as PHP). The idea is that one wouldn't have to implement anti-spam measures on a per app basis but have an "umbrella" of spam protection.

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  • How useful is mounting /tmp noexec?

    - by Novelocrat
    Many people (including the Securing Debian Manual) recommend mounting /tmp with the noexec,nodev,nosuid set of options. This is generally presented as one element of a 'defense-in-depth' strategy, by preventing the escalation of an attack that lets someone write a file, or an attack by a user with a legitimate account but no other writable space. Over time, however, I've encountered arguments (most prominently by Debian/Ubuntu Developer Colin Watson) that noexec is a useless measure, for a couple potential reasons: The user can run /lib/ld-linux.so <binary> in an attempt to get the same effect. The user can still run system-provided interpreters on scripts that can't be run directly Given these arguments, the potential need for more configuration (e.g. debconf likes an executable temporary directory), and the potential loss of convenience, is this a worthwhile security measure? What other holes do you know of that enable circumvention?

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  • What OS for Eee PC ?

    - by crivateos
    Hello. I've just bought new Eee PC 1005 (with Atom N450, 250GB and 2GB memory) without any pre-installed system. Now I'd like to install windows and linux distribution on in. What should I choose ? I am a programmer and web designer, so I need Java IDE , Python interpreters, and Photoshop (on windows). Will Win 7 Pro 32bit work ?Or should I choose Windows XP ? And what about linux distro ? Ubuntu, Eeebuntu, Ubuntu netbook edition ? btw is it true that linux's grub overrides mbr so that hardware system restore doesn't work ?

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  • Will you install software on the same partition as Windows system?

    - by Tim
    I was wondering if you always install software on the same partition as Windows 7 system? What kinds of software do you install on the same partition as Windows system? What kinds of software you install on another partition? If you install software on another partition, do you install them on a dedicated partition to these software? Or do you install them on the same partition as data (personal data)? How do you plan the sizes for the partition(s) in either case? What are to consider when making plans about the above questions? The software I am installing include: Matlab, Mathematica, IDEs, compilers or Interpreters for C++, C, Java, R, Python, Perl, Lisp, Latex, and database. Mainly for programming and typesetting kinds of studies and projects.

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  • Building a common syntax and scoping framework.

    - by Ben DeMott
    Hello fellow programmers, I was discussing a project the other day with a colleague of mine and I was curious to see what others had to say or if such a thing already existed. Background There are many programming languages. There are many IDE's and source editors that highlight and edit source code. Following perfectly and exactly the rules of a language to present auto-complete options and understand scopes in the code is rather complex. This task is complex enough that most IDE's implement different source-editors as plugins that often re-implement the same features over and over but in a different way (netbeans). From what I can tell most IDE's and source editors re-implement parsers that use regular expressions, or some meta-syntax Naur Form to describe the languages grammer generically. These parsers are implemented over and over and over again. Question Has anyone attempted to unify or describe a set of features through an API and have a consistent interface to parsing various programming languages and dialects. I'm not describing an IDE - but a consistent API for any program to use to parse and obtain meta-information from the source code. I realize various programming languages offer many different features which are difficult to 'abstract' into a set of features, but I feel this would be a worthwhile venture. It seems to me that this could possibly allow the authors of interpreters to help maintain a central grammer intepreter for their language. the Python foundation could maintain the Python grammer api, ANSI the C grammer api, Oracle the Java grammer API, etc Example usage If this was API existed code documentation generators could theoretically work across all dialects and languages to some level. It wouldn't matter if your project used 5 different languages a single application could document all of them and the comments and doc-tags within. Has anyone attempted this comprehensively?

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  • What is the difference between an Abstract Syntax Tree and a Concrete Syntax Tree?

    - by Jason Baker
    I've been reading a bit about how interpreters/compilers work, and one area where I'm getting confused is the difference between an AST and a CST. My understanding is that the parser makes a CST, hands it to the semantic analyzer which turns it into an AST. However, my understanding is that the semantic analyzer simply ensures that rules are followed. I don't really understand why it would actually make any changes to make it abstract rather than concrete. Is there something that I'm missing about the semantic analyzer, or is the difference between an AST and CST somewhat artificial?

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  • How can I sandbox Python in pure Python?

    - by Blixt
    I'm developing a web game in pure Python, and want some simple scripting available to allow for more dynamic game content. Game content can be added live by privileged users. It would be nice if the scripting language could be Python. However, it can't run with access to the environment the game runs on since a malicious user could wreak havoc which would be bad. Is it possible to run sandboxed Python in pure Python? If not, are there any open source script interpreters written in pure Python that I could use? The requirements are support for variables, basic conditionals and function calls (not definitions).

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  • Implementing Brainf*ck loops in an interpreter

    - by sub
    I want to build a Brainf*ck (Damn that name) interpreter in my freshly created programming language to prove it's turing-completeness. Now, everything is clear so far (<+-,.) - except one thing: The loops ([]). I assume that you know the (extremely hard) BF syntax from here on: How do I implement the BF loops in my interpreter? How could the pseudocode look like? What should I do when the interpreter reaches a loop beginning ([) or a loop end (])? Checking if the loop should continue or stop is not the problem (current cell==0), but: When and where do I have to check? How to know where the loop beginning is located? How to handle nested loops? As loops can be nested I suppose that I can't just use a variable containing the starting position of the current loop. I've seen very small BF interpreters implemented in various languages, I wonder how they managed to get the loops working but can't figure it out.

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  • Using different languages in one project

    - by Tarbal
    I recently heard about the use of several different languages in a (big) project, I also read about famous services such as Twitter using Rails as frontend, mixed with some other languages, and Scala I think it was as backend. Is this common practice? Who does that? I'm sure there are disadvantages to this. I think that you will have problems with the different interpreters/compilers and seamlessly connecting the different languages. Is this true? Why is this actually done? For performance?

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  • Python - question regarding the concurrent use of `multiprocess`.

    - by orokusaki
    I want to use Python's multiprocessing to do concurrent processing without using locks (locks to me are the opposite of multiprocessing) because I want to build up multiple reports from different resources at the exact same time during a web request (normally takes about 3 seconds but with multiprocessing I can do it in .5 seconds). My problem is that, if I expose such a feature to the web and get 10 users pulling the same report at the same time, I suddenly have 60 interpreters open at the same time (which would crash the system). Is this just the common sense result of using multiprocessing, or is there a trick to get around this potential nightmare? Thanks

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