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  • difference equations in MATLAB - why the need to switch signs?

    - by jefflovejapan
    Perhaps this is more of a math question than a MATLAB one, not really sure. I'm using MATLAB to compute an economic model - the New Hybrid ISLM model - and there's a confusing step where the author switches the sign of the solution. First, the author declares symbolic variables and sets up a system of difference equations. Note that the suffixes "a" and "2t" both mean "time t+1", "2a" means "time t+2" and "t" means "time t": %% --------------------------[2] MODEL proc-----------------------------%% % Define endogenous vars ('a' denotes t+1 values) syms y2a pi2a ya pia va y2t pi2t yt pit vt ; % Monetary policy rule ia = q1*ya+q2*pia; % ia = q1*(ya-yt)+q2*pia; %%option speed limit policy % Model equations IS = rho*y2a+(1-rho)yt-sigma(ia-pi2a)-ya; AS = beta*pi2a+(1-beta)*pit+alpha*ya-pia+va; dum1 = ya-y2t; dum2 = pia-pi2t; MPs = phi*vt-va; optcon = [IS ; AS ; dum1 ; dum2; MPs]; He then computes the matrix A: %% ------------------ [3] Linearization proc ------------------------%% % Differentiation xx = [y2a pi2a ya pia va y2t pi2t yt pit vt] ; % define vars jopt = jacobian(optcon,xx); % Define Linear Coefficients coef = eval(jopt); B = [ -coef(:,1:5) ] ; C = [ coef(:,6:10) ] ; % B[c(t+1) l(t+1) k(t+1) z(t+1)] = C[c(t) l(t) k(t) z(t)] A = inv(C)*B ; %(Linearized reduced form ) As far as I understand, this A is the solution to the system. It's the matrix that turns time t+1 and t+2 variables into t and t+1 variables (it's a forward-looking model). My question is essentially why is it necessary to reverse the signs of all the partial derivatives in B in order to get this solution? I'm talking about this step: B = [ -coef(:,1:5) ] ; Reversing the sign here obviously reverses the sign of every component of A, but I don't have a clear understanding of why it's necessary. My apologies if the question is unclear or if this isn't the best place to ask.

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  • Access variables from a number of sources

    - by mac_55
    I'm creating my first game, and I've currently set up a 'GameState' class, to store player health etc. inside. This class is currently instantiated from the AppDelegate as I need to access it from all over my game. This is fine. For each class I'm working in, I can access the app delegate, and then find the GameState object... however, it seems very messy. I'm tempted to find a way (I'm still a newbie) to define the GameState instance as being some sort of global variable so that I can access it from all over with ease... but my little bit of reading on variable scope makes me uneasy about doing this, even if I knew how. Any ideas of the best way to define and access this class? It'll be used for everything from player health, to items they've found, any personalisation etc. Thanks!

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  • Adding an element to a list in Scheme

    - by user272483
    I'm using R5RS Scheme and I just want to implement a function that returns the intersection of two given lists, but I can't do that because I cannot add an element to a list. Here is my code. How can I fix it? I'm really a beginner in Scheme - this is my first work using Scheme. thx in advance.. (define list3 '()) (define (E7 list1 list2) (cond ((null? list1) list3) ((member (car list1) list2) (append list3 (list (car list1)))) ) (cond ((null? list1) list3) ((not(null? list1)) (E7 (cdr list1) list2) ) ) ) (E7 '(4 5) '(3 4))

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  • Jquery Text Variable

    - by Batfan
    I am trying to get jquery to pick up variable that I am defining and I'm having issues doing it. $.ajax({ url: "sitemap.php", cache: false, success: function(html){ $("#results").append(html); var $seriestitle = $("#define-title").text(); $('#results a:contains("$seriestitle")').addClass('current-series'); $('a:not(".current-series")').hide(); } }); This is the code I am using. You can view the page at the following URL: http://benjammindesigns.com/XML/details/1231.html There is a span on the page, with the ID 'define-title', that contains text. I am trying to pull the text from that span and use it as my variable. Any info is greatly appreciated.

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  • How to pass Endpoint parameter to Endpoint defined as bean in Spring conext

    - by sempa
    I have camel Fileendpoint defined in following way: <bean id="hotfolderEndpoint" class="org.apache.camel.component.file.FileEndpoint" factory-bean="camel" factory-method="getEndpoint"> <constructor-arg ref="hotfolder" /> </bean> I want to define some File parameters such as preMove, move etc. Variable hotfolder is String taken from JNDI and I have no impact on it. When I define property as <bean id="moveExp" class="org.apache.camel.model.language.SimpleExpression"> <property name="expression" value="done/${file:name}"/> </bean> it is not correctly parsed and the file get name done/name

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  • javascript arrays: adding entries

    - by Lyon
    Hi, I'm not sure how I would do this in Javascript. I want to create an array that would contain any number of error messages from my form. I read on websites that you define the key for that array when adding new entries. // Javascript var messages = new Array(); messages[0] = 'Message 1'; How can I add entries into my array using a similar method I normally do in PHP // PHP $messages = array(); $messages[] = 'Message 1'; // automatically assigned key 0 $messages[] = 'Message 2'; // automatically assigned key 1 Is it possible to emulate that in Javascript? I don't want to have to define the number of entries in my array as it can vary. Thanks for helping me out on this very basic js question. -Lyon

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  • Transportation Web App - utilizing google or bing map api

    - by BillS
    I am working on a transportation web app and I am having a bit of a problem. First, I want to be able to define a shipping corridor, say like I-95 between Baltimore MD and Richmond VA. And store what parameters I need to define this route. Users will then use a web interface and can select various routes, in this case, I-95. Vendors will be posting constantly changing pickup locations in the application database which have a shelf life of about 2 days. Some of these locations maybe along this route. I am storing the LAT and LONG for the specific location right now. If any of these points ARE along or within 2 mile of the route (just off the highway basically - the ideal check would based on an actual highway exit but at this point anything would work), I want them to show up in my search results. Any ideas or suggestions?

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  • Slime in emacs seems has conflicts with autopair

    - by Boris
    I have just install slime in emacs. And after removed all the other plugins for debuging, I found that slime seems had conflicts with autopair.(Or a bug of autopair?).In slime, when I typed C-c C-c, the minibuffer displayed error like: error in process filter: define-key: Wrong type argument: characterp, nil error in process filter: Wrong type argument: characterp, nil error in process filter: define-key: Wrong type argument: characterp, nil error in process filter: Wrong type argument: characterp, nil Even more, the error message still alerted after I killed the slime buffer. If I also remove the autopair plugin, slime works just fine. Can anyone tell me how to solve this? Thanks. :)

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  • Issue in exec method

    - by mukul sharma
    Hi all, I am a having two python files file1.py and file2.py. I am using exec() to get the method/Variables defined in the file2.py. file1.py have a class as given below class one: def init(self): self.HOOK = None exec(file2.py) self.HOOK = Generate ### call the hook method #### self.HOOK() file2.py looks like as (There is no class define in file2.py) def Generate() do 1 do 2 Hello() def hello() print "hello" Now the problem is as When i run script it is giving a error global name Hello not found. If i remove Hello() from Generate method in file2.py then its work fine. I cant use import file2.py in file1.py,because in file2.py the only one method name (Generate) is fix (its taken as requirement). So apart from Genarate method user can define any method and can call this in generate method, because this approach is not working so i have to write whole code into generate method only and code is also repetitive. Any help is really appreciable...

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  • In SICP exercise 2.26 using DrScheme, why does cons return a list, instead of a pair of lists?

    - by limist
    In SICP exercise 2.26, this Scheme code is given: (define x (list 1 2 3)) (define y (list 4 5 6)) Then this cons call is given: (cons x y) I expected a pair of lists would result, ((1 2 3) (4 5 6)) but the interpreter gives, ((1 2 3) 4 5 6) ...a list with 4 elements, the first being a list. Why is y treated differently? I've tried looking up other SICP answers for an explanation, but couldn't find something satisfactory. So could any Scheme/Lisp experts please shed some light on this aspect of cons? Thanks in advance for any insight.

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  • Create an grid array...

    - by Anicho
    Okay so I am looking to create a grided array in OGRE3D game engine but the array is generic my array skills are pretty basic and need work so I am posting this just to be sure I am doing this correctly. #define GRIDWIDTH 10 #define GRIDHEIGHT 10 int myGrid [HEIGHT][WIDTH]; int n,m; int main () { for (n=0;n<HEIGHT;n++) for (m=0;m<WIDTH;m++) { jimmy[n][m]=(n+1)*(m+1); } return 0; } I am assuming the above will return: 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 Then I can assign each point in the array to a valid node in OGRE3D to create a grid in 3D view would this work? Just need to tell me if I am doing it right or wrong dont need the ogre3d code....

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  • OpenAL - determine maximum sources

    - by Bill Kotsias
    Is there an API that allows you to define the maximum number of OpenAL "sources" allowed by the underlying sound hardware? Searching the internet, I found 2 recommendations : keep generating OpenAL sources till you get an error. However, there is a note in FreeSL (OpenAL wrapper) stating that this is "very bad and may even crash the library" assume you only have 16; why would anyone ever require more? (!) The second recommendation is even adopted by FreeSL. So, is there a common API to define the number of simultaneous "voices" supported? Thank you for your time, Bill

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  • PHPDelicious - Fail to Connect to Delicious

    - by Meander365
    phpdelicious (http://www.phpdelicious.com/) is a wrapper class for pulling in your delicious bookmarks using php. But I can't get it to work. Here's my code - my index.php: <?php require('php-delicious.inc.php'); define('DELICIOUS_USER', 'my-user-name-here'); define('DELICIOUS_PASS', 'my-password-here'); $oDelicious = new PhpDelicious(DELICIOUS_USER, DELICIOUS_PASS); ?> <?php if ($aPosts = $oDelicious->GetAllPosts()) { foreach ($aPosts as $aPost) { echo '<a href="'.$aPost['url'].'">'.$aPost['desc'].'</a>'; echo $aPost['notes']; echo $aPost['updated']; } } else { echo $oDelicious->LastErrorString(); } ?> But I get this error : Notice: Use of undefined constant CACHE_PATH - assumed 'CACHE_PATH' in C:\wamp\www\testing\cache.inc.php on line 44 Connection to del.icio.us failed. Any ideas?

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  • directx 9 hlsl vs. directx 10 hlsl : syntex the same.

    - by numerical25
    For the past month or so I been busting my behind trying to learn directx. So I been mixing back back and fourth from directx 9 to directx 10. One of the major changes I've seen in the two is how to process vectors in the graphics card. one of the drastic changes I notice is how you get the gpu to recognize your structs. In directx 9 you define the Flexible Vertex Formats your typical set up would be like this... #define CUSTOMFVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE) in directx 10 I believe the equivalent is the input vertex description D3D10_INPUT_ELEMENT_DESC layout[] = { {"POSITION",0,DXGI_FORMAT_R32G32B32_FLOAT, 0 , 0, D3D10_INPUT_PER_VERTEX_DATA, 0}, {"COLOR",0,DXGI_FORMAT_R32G32B32A32_FLOAT, 0 , 12, D3D10_INPUT_PER_VERTEX_DATA, 0} }; I notice in directx 10. it is more descriptive. besides this, what are some of the drastic changes made. and is the hlsl syntax the same for both.

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  • What's the diffrence btw System property and system environment variable

    - by khue
    Hi all I am not clear about this. When I run a java App or run an Applet in applet viewer,( in the IDE environment), System.getProperty("java.class.path") give me the same as System.getenv("CLASSPATH"), which is the CLASSPATH env variable defined. But when I deploy my applet to webserver and access it from the same computer as a client, I get different result for the two (System.getProperty("java.class.path") only point to jre home and System.getenv("CLASSPATH") return null). And here is some other things that make me wonder: For the applet part, the env var JAVA_HOME, i get the same result when deploying the applet in a browser as well as Applet Viewer. And if I define myself a env variable at system level, and use getenv("envName") the result is null. Is there anyway I can define one and get it in my java program? Thanks a lot Regards K.

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  • C language preprocessor behavior

    - by khanna_param
    There are different kind of macros in C language, nested macro is one of them. Considering a program with the following macro #define HYPE(x,y) (SQUR(x)+SQUR(y)) #define SQUR(x) (x*x) Using this we can successfully compile to get the result. As we all know the C preprocessor replaces all the occurrence of the identifiers with the replacement-string. Considering the above example I would like to know how many times the C preprocessor traverses the program to replace the macro with the replacement values. I assume it cannot be done in one go.

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  • compile cs files with mono?

    - by acidzombie24
    I am trying to compile my project with mono on linux. My cmd looks something like... gmcs Pages/UserProfile.cs Properties/AssemblyInfo.cs queues.cs watch_editor.cs Class1.cs -define:USE_SQLITE -r:System -r:System.Collections -r:System.Collections.Generic -r:System.Collections.ObjectModel -r:System.Collections.Specialized -r:System.Configuration but much long. and i get the output error CS0006: cannot find metadata file `System.Collections' error CS0006: cannot find metadata file `System.Collections.Generic' error CS0006: cannot find metadata file `System.Collections.ObjectModel' ... How do i solve this? I also tried it the other way around (below) and had the same error msg with .dll at the end of them gmcs -define:USE_SQLITE -r:System.dll -r:System.Collections.dll -r:System.Web.UI.WebControls CommentCenter.cs cookies.cs db.cs Default.aspx.cs

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  • C# Getting Just Date From Timestamp

    - by Soo
    If I have a timestamp in the form: yyyy-mm-dd hh:mm:ss:mmm How can I just extract the date from the timestamp? For instance, if a timestamp reads: "2010-05-18 08:36:52:236" what is the best way to just get 2010-05-18 from it. What I'm trying to do is isolate the date portion of the timestamp, define a custom time for it to create a new time stamp. Is there a more efficient way to define the time of the timestamp without first taking out the date, and then adding a new time?

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  • Looking for Reachability (2.0) Use Case Validation

    - by user350243
    There is so much info out there on using Apple's Reachability example, and so much is conflicting. I'm trying to find out of I'm using it (Reachability 2.0) correctly below. My App use case is this: If an internet connection is available through any means (wifi, LAN, Edge, 3G, etc.) a UIButton ("See More") is visible on various views. If no connection, the button is not visible. The "See More" part is NOT critical in any way to the app, it's just an add-on feature. "See More" could be visible or not anytime during the application lifecycle as connection is established or lost. Here's how I did it - Is this correct and/or is there a better way? Any help is Greatly Appreciated! lq // AppDelegate.h #import "RootViewController.h" @class Reachability; @interface AppDelegate : NSObject <UIApplicationDelegate> { UIWindow *window; UINavigationController *navigationController; RootViewController *rootViewController; Reachability* hostReach; // NOT USED: Reachability* internetReach; // NOT USED: Reachability* wifiReach; } @property (nonatomic, retain) IBOutlet UIWindow *window; @property (nonatomic, retain) IBOutlet UINavigationController *navigationController; @property (nonatomic, retain) IBOutlet RootViewController *rootViewController; @end // AppDelegate.m #import "AppDelegate.h" #import "Reachability.h" #define kHostName @"www.somewebsite.com" @implementation AppDelegate @synthesize window; @synthesize navigationController; @synthesize rootViewController; - (void) updateInterfaceWithReachability: (Reachability*) curReach { if(curReach == hostReach) { NetworkStatus netStatus = [curReach currentReachabilityStatus]; BOOL connectionRequired = [curReach connectionRequired]; // Set a Reachability BOOL value flag in rootViewController // to be referenced when opening various views if ((netStatus != ReachableViaWiFi) && (netStatus != ReachableViaWWAN)) { rootViewController.bConnection = (BOOL *)0; } else { rootViewController.bConnection = (BOOL *)1; } } } - (void) reachabilityChanged: (NSNotification* )note { Reachability* curReach = [note object]; NSParameterAssert([curReach isKindOfClass: [Reachability class]]); [self updateInterfaceWithReachability: curReach]; } - (void)applicationDidFinishLaunching:(UIApplication *)application { // NOTE: #DEFINE in Reachability.h: // #define kReachabilityChangedNotification @"kNetworkReachabilityChangedNotification" [[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(reachabilityChanged:) name: kReachabilityChangedNotification object: nil]; hostReach = [[Reachability reachabilityWithHostName: kHostName] retain]; [hostReach startNotifer]; [self updateInterfaceWithReachability: hostReach]; [window addSubview:[navigationController view]]; [window makeKeyAndVisible]; } - (void)dealloc { [navigationController release]; [rootViewController release]; [window release]; [super dealloc]; } @end

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  • adding an element to a list in lisp

    - by user272483
    i'm using r5rs and i just want to implement a function that returns the intersection of two given lists but i can't do that because i can npot add element to a list. here is my code. how can i fix it? i'm really a beginner in lisp, this is my first work on lisp? thx in advance.. (define list3 '()) (define (E7 list1 list2) (cond ((null? list1) list3) ((member (car list1) list2) (append list3 (list (car list1)))) ) (cond ((null? list1) list3) ((not(null? list1)) (E7 (cdr list1) list2) ) ) ) (E7 '(4 5) '(3 4))

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  • C++ - dynamic pointer of array

    - by Eagle
    Hi to all, first i would like to say i am Newbie in C++. As part of my master thesis i am writing a program in C++ which also get as parameters the variables m and d (both integers). Were d is the power of 2 (this means 2^d elements). Parameter m define the number of possible interactions between one element and the total group (2^d elements). The number of possible interactions is computed as following: \kappa = \sum_{i=0}^m\binom{d}{i} (at present i generate vector of vectors for 2^d x \kappa, but my Prof. would like me to create different statistics to different m's. My first though was to to generate a dynamic array of m arrays of different sizes... Then i though of defining a 3-dim array with the biggest needed 2d array, but also program speed is important (e.g d = 20). i would like to ask for your advice how to define such kind of dynamic array that will also be fast. Regards

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  • DirectX 9 HLSL vs. DirectX 10 HLSL: syntax the same?

    - by numerical25
    For the past month or so, I have been busting my behind trying to learn DirectX. So I've been mixing back back and forth between DirectX 9 and 10. One of the major changes I've seen in the two is how to process vectors in the graphics card. One of the drastic changes I notice is how you get the GPU to recognize your structs. In DirectX 9, you define the Flexible Vertex Formats. Your typical set up would be like this: #define CUSTOMFVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE) In DirectX 10, I believe the equivalent is the input vertex description: D3D10_INPUT_ELEMENT_DESC layout[] = { {"POSITION",0,DXGI_FORMAT_R32G32B32_FLOAT, 0 , 0, D3D10_INPUT_PER_VERTEX_DATA, 0}, {"COLOR",0,DXGI_FORMAT_R32G32B32A32_FLOAT, 0 , 12, D3D10_INPUT_PER_VERTEX_DATA, 0} }; I notice in DirectX 10 that it is more descriptive. Besides this, what are some of the drastic changes made, and is the HLSL syntax the same for both?

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  • Static struct in C++

    - by pingvinus
    Hi, I want to define an structure, where some math constants would be stored. Here what I've got now: struct consts { //salt density kg/m3 static const double gamma; }; const double consts::gamma = 2350; It works fine, but there would be more than 10 floating point constants, so I doesn't want to wrote 'static const' before each of them. And define something like that: static const struct consts { //salt density kg/m3 double gamma; }; const double consts::gamma = 2350; It look fine, but I got these errors: 1. member function redeclaration not allowed 2. a nonstatic data member may not be defined outside its class I wondering if there any C++ way to do it?

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  • Pros and Cons of Different macro function / inline methods in C

    - by Robert S. Barnes
    According to the C FAQ, there are basically 3 practical methods for "inlining" code in C: #define MACRO(arg1, arg2) do { \ /* declarations */ \ stmt1; \ stmt2; \ /* ... */ \ } while(0) /* (no trailing ; ) */ or #define FUNC(arg1, arg2) (expr1, expr2, expr3) To clarify this one, the arguments are used in the expressions, and the comma operator returns the value of the last expression. or using the inline declaration which is supported as an extension to gcc and in the c99 standard. The do { ... } while (0) method is widely used in the Linux kernel, but I haven't encountered the other two methods very often if at all. I'm referring specifically to multi-statement "functions", not single statement ones like MAX or MIN. What are the pros and cons of each method, and why would you choose one over the other in various situations?

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  • Executing certain code for every method call in C++

    - by Luís Guilherme
    I have a C++ class I want to inspect. So, I would like to all methods print their parameters and the return, just before getting out. The latter looks somewhat easy. If I do return() for everything, a macro #define return(a) cout << (a) << endl; return (a) would do it (might be wrong) if I padronize all returns to parenthesized (or whatever this may be called). If I want to take this out, just comment out the define. However, printing inputs seems more difficult. Is there a way I can do it, using C++ structures or with a workaroud hack?

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