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  • How to implement arrays in an interpreter?

    - by Ray
    I have managed to write several interpreters including Tokenizing Parsing, including more complicated expressions such as ((x+y)*z)/2 Building bytecode from syntax trees Actual bytecode execution What I didn't manage: Implementation of dictionaries/lists/arrays. I always got stuck with getting multiple values into one variable. My value structure (used for all values passed around, including variables) looks like this, for example: class Value { public: ValueType type; int integerValue; string stringValue; } Works fine with integers and strings, but how could I implement arrays? (From now on with array I mean arrays in my experimental language, not in C++) How can I fit the array concept into the Value class above? Is it possible? How should I make arrays able to be passed around just as you could pass around integers and strings in my language, using the class above? Accessing array elements or memory allocation wouldn't be the problem, I just don't know how to store them.

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  • No method 'get' on backbone model save

    - by user888734
    I'm using backbone for a reasonably complicated form. I have a number of nested models, and have been computing other variables in the parent model like so: // INSIDE PARENT MODEL computedValue: function () { var value = this.get('childModel').get('childModelProperty'); return value; } This seems to work fine for keeping my UI in sync, but as soon as I call .save() on the parent model, I get: Uncaught TypeError: Object #<Object> has no method 'get' It seems that the child model kind of temporarily stops responding. Am I doing something inherently wrong? EDIT: The stack trace is: Uncaught TypeError: Object #<Object> has no method 'get' publish.js:90 Backbone.Model.extend.neutralDivisionComputer publish.js:90 Backbone.Model.extend.setNeutralComputed publish.js:39 Backbone.Events.trigger backbone.js:163 _.extend.change backbone.js:473 _.extend.set backbone.js:314 _.extend.save.options.success backbone.js:385 f.Callbacks.o jquery.min.js:2 f.Callbacks.p.fireWith jquery.min.js:2 w jquery.min.js:4 f.support.ajax.f.ajaxTransport.send.d

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  • SendMessage videocapture consts

    - by Rita
    Hello, I am using a code sample to connect to a webcam, and don't really understand the meaning of the variables passed to the SendMessage method. SendMessage(DeviceHandle, WM_CAP_SET_SCALE, -1, 0) SendMessage(DeviceHandle, WM_CAP_SET_PREVIEW, -1, 0) What does the -1 mean? To scale/preview or not to scale/preview? I'd prefer that zero/one would be used, zero meaning false, and have no idea what the -1 means. SendMessage(DeviceHandle, WM_CAP_EDIT_COPY, 0, 0); What does the zero mean in this case? Or does this message is simply void and the zero has no meaning, similar to the last zero argument? Btw, what DOES the last zero argument mean? Thank you very much in advance :)

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  • Static vs Non Static constructors

    - by Neil N
    I can't think of any reasons why one is better than the other. Compare these two implementations: public class MyClass { public myClass(string fileName) { // some code... } } as opposed to: public class MyClass { private myClass(){} public static Create(string fileName) { // some code... } } There are some places in the .Net framework that use the static method to create instances. At first I was thinking, it registers it's instances to keep track of them, but regular constructors could do the same thing through the use of private static variables. What is the reasoning behind this style?

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  • Is it possible to reference object within the same object?

    - by fudgey
    I've been messing around with jQuery plugin code and I'm trying to put all of my common variables into a single object for easy access. I have included a few examples below on how I've done this, but I'm wondering how others deal with this problem. Lets say I have this var x = function(options){ var defaults = { ulist : $('ul#list'), listLen : $('ul#list').children().length } $.extend(options, defaults); // do other stuff } What I'm trying to do is use the ulist object in as a base, then find the number of li's I guess I could do this: var x = function(options){ var defaults = { ulist : $('ul#list'), listLen : 0 } defaults.listLen = defaults.ulist.children().length; $.extend(options, defaults); // do other stuff } or this: var x = function(options){ var defaults = { ulist : $('ul#list') }; var defaults2 = { listLen : defaults.ulist.children().length } $.extend(defaults, defaults2); $.extend(options, defaults); // do other stuff } The above code samples are just thrown together, and only meant to get the idea across to you. Anyway, is there a better way to do this?

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  • htaccess for swf file

    - by Charles Wayne
    Does htaccess works with swf file that accepts variables? I have this swf url... http://subdom.domain.tld/subfolder/live.swf?stream=rtmp://stream.domain.com/application&provider=rtmp&file=streamname&autostart=true I want it to be rewrite as http://subdom.domain.tld/subfolder/assignedname/ So far this is what I written on .htaccess file RewriteEngine On RewriteRule ^kwt/?$ live.swf?stream=rtmp://stream.domain.com/application&provider=rtmp&file=streamname&autostart=true [NC,L] It does seem to rewrite to the swf file because the swf is showing but for some reason the variable is not recognized. It does not auto play even the auto play variable is set to true in the RewriteRule. Is there something wrong with my code or it can't be done in swf file?

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  • wordpress filters documentation? Trying to understand add_filter()

    - by Chris J. Lee
    I read over the documentation several times and have been having a hard time trying to figure out what is going on with the function. I'm more and more confused after looking at the documentation, looking over the source code as well. add_filter($tag, $hook, $priority, $args); it seems to me the new function extends the parent function. What puzzle's me is what parts of the hook becomes overridden. in some examples in the documentation i see that some variables are replaced with the $args in your new $tag. I almost understood it all here: http://www.andrewnacin.com/2010/05/18/rethinking-template-tags-in-plugins/ but then i couldn't figure out how you pass arguments and which eventually get overriden. thanks in advance.

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  • saving a records containing a member of type string to a file (Delphi, Windows)

    - by wonderer
    I have a record that looks similar to: type TNote = record Title : string; Note : string; Index : integer; end; Simple. The reason I chose to set the variables as string (as opposed to an array of chars) is that I have no idea how long those strings are going to be. They can be 1 char long, 200 or 2000. Of course when I try to save the record to a type file (file of...) the compiler complains that I have to give a size to string. Is there a way to overcome this? or a way to save those records to an untyped file and still maintain a sort of searchable way? Please do not point me to possible solutions, if you know the solution please post code. Thank you

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  • Mutual Information / Entropy Calculation Help

    - by Fillip
    Hi, Hoping someone can give me some pointers with this entropy problem. Say X is chosen randomly from the uniform integer distribution 0-32 (inclusive). I calculate the entropy, H(X) = 32 bits, as each Xi has equal probability of occurring. Now, say the following pseudocode executes. int r = rand(0,1); // a random integer 0 or 1 r = r * 33 + X; How would I work out the mutual information between the two variables r and X? Mutual Information is defined as I(X; Y) = H(X) - H(X|Y) but I don't really understand how to apply the conditional entropy H(X|Y) to this problem. Thanks

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  • Issue with plotting daily data using ggplot

    - by user1723765
    I tried to plot daily data from 9 variables in ggplot, but the graph I get cannot handle the date variable properly. The x axis is unreadable and its impossible to read the plot. I'm guessing there's an issue with the handling of dates. Here's the data: https://dl.dropbox.com/u/22681355/su.csv Here's the code I've been using: su=read.csv(file="su.csv", head=TRUE) meltdf=melt(su) ggplot(meltdf, aes(x=Date, y=value, colour=variable, group=variable))+geom_line() and here's the output: https://dl.dropbox.com/u/22681355/output.jpg here's the same plot done in excel, why does it look completely different?

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  • Cuda program results are always zero in HW, correct in EMU??

    - by Orion Nebula
    Hi all! I am having a weird problem .. I have written a CUDA code which executes correctly in emulation and all results show up.. however, when executed on hardware "G210" .. the results in the result memory are always 0 I am passing two vectors to the kernel, one with random variables the other is initialized to zero, the code copies the first vector to shared memory, does some swapping and other operations and then writes back the results on the second vector (the one with the initial 0's) I am using double precision, the -arch sm13 flag is used, all memory allocation also use sizeof(double) .. I have checked if the kernel is invoked, it does .. so no problems here .. the cudaMemCpy has no problems .. what could be the problem .. :( why would it work in emulation but not on HW I am quite confused .. any ideas?

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  • Does retrieving an object from Doctrine2 cause __construct() of the model class to run?

    - by jiewmeng
    When I retrieve an object say by $em->find('Application\Models\User', 1); or other methods like DQL, findBy*() cause the __construct() of the model class to run? I am having a problem where I set variables there like reference to EntityManager and I find that its not set. I tried putting a die() in __construct() and it doesn't halt the application. Can I say that if I want to set other properties/fields like EntityManager $em I have to do it some other way? Perhaps something like protected function getEm() { if (!isset($this->em)) { $this->em = \Zend_Registry::get('em'); } return $this->em; }

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  • design pattern tools to use?

    - by ajsie
    i have noticed that every area has some tools you can use to make things easier. eg. css = dreamweaver doctrine/propel = orm designer // you dont have to hardcore code schemas manually and remembering all the syntax/variables mysql = mysql workbench // the same etc. in this way you get aided and dont have to type things the hard way, and can learn the structure, but then use GUI tools to help you develop faster. now i'm learning design patterns (singleton, factory, command, memento etc) and im wondering if there are some kind of tools you can use that will help you develop faster. i dont know exactly what tools i'm trying to find, just helping me when coding with design patterns (schema drawings? references?) are there any?

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  • C: Incompatible types?

    - by Airjoe
    #include <stdlib.h> #include <stdio.h> struct foo{ int id; char *bar; char *baz[6]; }; int main(int argc, char **argv){ struct foo f; f.id=1; char *qux[6]; f.bar=argv[0]; f.baz=qux; // Marked line return 1; } This is just some test code so ignore that qux doesn't actually have anything useful in it. I'm getting an error on the marked line, incompatible types when assigning to type ‘char *[6]’ from type ‘char **’ but both of the variables are defined as char *[6] in the code. Any insight?

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  • Commenting out protect_from_forgery

    - by Andy
    Hi, I was trying to use active record store but I kept getting an invalid authenticity token. Someone told me to remove my protect_from_forgery from application controller. I know that this would remove all auth tokens but I'm not sure if this is a good idea. Does active record store not need auth tokens? By the way, all I need is a way to dynamically calculate the number of users online and their session variables. If there is a better way than using active record store it would be nice to know.

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  • Autorelease with elements in a UITableViewCell - memory leak

    - by Shaun Budhram
    In my 'cellForRowAtIndexPath' method for a UITableView delegate, I'm allocating a cell if it doesn't exist, and in this cell, I'm creating a new activity spinner like so: UIActivityIndicatorView *actView = [[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray ] autorelease]; I'm using Leaks to detect memory leaks in my program, and for some reason, this is coming up as a leak, even though it's autoreleasing. The cell itself is also autoreleasing. Has anyone had experience with autoreleasing variables coming up as leaks in the Leaks instrument, and how to tackle these problems? Also, if it helps, this is the history Leaks is displaying for this memory location. It looks like it at some point gets an additional retain message? This is not being done in my code.

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  • Xcodebuild failing to pick up environment values from project file?

    - by egrunin
    I'm using Xcode 3.2.6, MacOSX. I have a globally visible environment setting: ICU_SRC=~/Documents/icu/source This really is an environment setting, it's set at login time. When I open up Terminal, it's there. In my project, under Header Search Paths I've added this: $(ICU_SRC)/i18n $(ICU_SRC)/common These expand correctly when I compile inside the IDE. When I look at the build results, I see this: -I/Users/eric.grunin/Documents/icu/source/i18n -I/Users/eric.grunin/Documents/icu/source/common When I build from the command line, however, it fails. What I see is this: -I/i18n -I/common Here's the command I'm using to compile: /usr/bin/env -i xcodebuild -project my_project.xcodeproj -target "my_program" -configuration Release -sdk macosx10.6 build What am I doing wrong? Edited to add: Apple explains Setting environment variables for user processes

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  • Integers in JavaScript

    - by muntoo
    I'm a beginner to Javascript so forgive me if I sound dumb because I learned some Javascript from W3Fools (which are really difficult tutorials - they don't explain anything I want to know, but everything I probably can guess from my experience with C++). I may be switching over to MDN, but if you can recommend any other tutorials, that be great. Anyways, so here's my question: I just read a few lines of this, and apparently: Numbers in JavaScript are "double-precision 64-bit format IEEE 754 values", according to the spec. This has some interesting consequences. There's no such thing as an integer in JavaScript, so you have to be a little careful with your arithmetic if you're used to math in C or Java. I've already seen that there are few of the data types (for variables) I'm used to from C++. But I didn't expect all numbers to automatically be floats. Isn't there any way to use integers, not float? Will a future version of JavaScript support ints?

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  • Why do C++ streams use char instead of unsigned char?

    - by Johannes Schaub - litb
    I've always wondered why the C++ Standard library has instantiated basic_[io]stream and all its variants using the char type instead of the unsigned char type. char means (depending on whether it is signed or not) you can have overflow and underflow for operations like get(), which will lead to implementation-defined value of the variables involved. Another example is when you want to output a byte, unformatted, to an ostream using its put function. Any ideas? Note: I'm still not really convinced. So if you know the definitive answer, you can still post it indeed.

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  • Are raw C++ pointers first class objects?

    - by Shailesh Kumar
    According to Wikipedia: An object is first-class when it: can be stored in variables and data structures can be passed as a parameter to a subroutine can be returned as the result of a subroutine can be constructed at runtime has intrinsic identity (independent of any given name) Somebody had once told me that raw pointers are not first class objects while smart pointers like std::auto_ptr are. But to me, a raw pointer (to an object or to a function) in C++ does seem to me to satisfy the conditions stated above to qualify as a first class object. Am I missing something?

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  • C++ class initialisation containing class variable initialization

    - by Phil Hannent
    I noticed some code of a colleague today that initialized class variables in the initialization. However it was causing a warning, he says because of the order they are in. My question is why is it better to do variable initialization where it currently is and not within the curly brackets? DiagramScene::DiagramScene( int slideNo, QRectF screenRect, MainWindow* parent ) : QGraphicsScene( screenRect, parent ), myParent( parent ), slideUndoImageCurrentIndex(-1), nextGroupID(0), m_undoInProgress(false), m_deleteItemOnNextUndo(0) line(0), path(0) { /* Setup default brush for background */ scDetail->bgBrush.setStyle(Qt::SolidPattern); scDetail->bgBrush.setColor(Qt::white); setBackgroundBrush(scDetail->bgBrush); }

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  • Different Paramater Value Results In Slow Query

    - by alphadogg
    I have an sproc in SQL Server 2008. It basically builds a string, and then runs the query using EXEC(): SELECT * FROM [dbo].[StaffRequestExtInfo] WITH(nolock,readuncommitted) WHERE [NoteDt] < @EndDt AND [NoteTypeCode] = @RequestTypeO AND ([FNoteDt] >= @StartDt AND [FNoteDt] <= @EndDt) AND [FStaffID] = @StaffID AND [FNoteTypeCode]<>@RequestTypeC ORDER BY [LocName] ASC,[NoteID] ASC,[CNoteDt] ASC All but @RequestTypeO and @RequestTypeF are passed in as sproc parameters. The other two are built from a parameter into local variables. Normally, the query runs under one second. However, for one particular value of @StaffID, the execution plan is different and about 30x slower. In either case, the amount of data returned is generally the same, but execution time goes way up. I tried to recompile the sproc. I also tried to "copy" @StaffID into a local @LocalStaffID. Neither approach made any difference. Any ideas?

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  • PHP session values lost after redirect on one script but preserved after redirection on another.

    - by Iuhiz
    On my registration script i have: // Save registration information into the database // Set sessions $_SESSION['var1'] = 'somevalue'; $_SESSION['var2'] = 'anothervalue'; header('Location: /somewhere'); exit(); Then on my login script i have: // Check if user provided correct login credentials if (correct) { $_SESSION['var1'] = 'somevalue'; $_SESSION['var2'] = 'anothervalue'; } header('Location: /somewhere'); exit(); What happened is that the session variables were lost after the header redirect in the registration script but they were preserved after the redirect in the login script. I've checked session_id() at both pages and they have the same value, included session_start() at the top of every page and basically tried the solutions to this common problem found on Stackoverflow but somehow nothing seemed to work. I'm beginning to wonder if it is something to do with my server configuration instead of my code.

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  • R: how can I concatenate a list?

    - by John
    I'm trying to produce a single variable which is a concatenation of two chars e.g to go from "p30s4" "p28s4" to "p30s4 p28s4". I've tried cat and paste as shown below. Both return empty variables. What am I doing wrong? > blah = c("p30s4","p28s4") > blah [1] "p30s4" "p28s4" > foo = cat(blah) p30s4 p28s4 > foo NULL > foo = paste(cat(blah)) p30s4 p28s4 > foo character(0)

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  • Programming language for fast calculations with big integers

    - by sub
    I'm doing Project Euler problems at the moment and I can solve most of them using my own programming language which uses direct C++ integers (so they are bound to 2^32 on my machine). However, at times there are problems which require me to work with very high numbers, I can't do that with native integers. So I implemented a BigInt library in my language which unfortunately gets extremely slow at times. Is there a programming language suitable for very efficient handling of big numbers? I mean that I want to do the things I could do in other programming languages with it (variables, loops, etc.), but in a faster way. If you have got tips for workarounds of the 2^32 limit in my language/C++/other languages, please tell me too!

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