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  • extract data from an array without using loop in R

    - by Manolo
    I have a vector v with row positions: v<-c(10,3,100,50,...) with those positions I want to extract elements of a matrix, having a column fixed, for example lets suppose my column number is 2, so I am doing: data<-c() data<-c(matrix[[v]][[2]]) matrix has the data in the following format: [[34]] [1] "200_s_at" "4853" "1910" "3554" "2658" So for example, I want to extract from the row 342 the value 1910 only, column 2, and do the same with the next rows but I got an error when I want to do that, is it possible to do it directly? or should I have a loop that read one by one the positions in v and fill the data vector like: #algorithm for i<-1 to length(v) pos<-v[i] data[[i]]<-c(matriz[[pos]][[2]]) next i Thanks

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  • Stack Overflow Accessing Large Vector

    - by cam
    I'm getting a stack overflow on the first iteration of this for loop for (int q = 0; q < SIZEN; q++) { cout<<nList[q]<<" "; } nList is a vector of type int with 376 items. The size of nList depends on a constant defined in the program. The program works for every value up to 376, then after 376 it stops working. Any thoughts?

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  • C++/Qt - Memory allocation question

    - by HardCoder1986
    Hello! I recently started investigating Qt for myself and have the following question: Suppose I have some QTreeWidget* widget. At some moment I want to add some items to it and this is done via the following call: QList<QTreeWidgetItem*> items; // Prepare the items QTreeWidgetItem* item1 = new QTreeWidgetItem(...); QTreeWidgetItem* item2 = new QTreeWidgetItem(...); items.append(item1); items.append(item2); widget->addTopLevelItems(items); So far it looks ok, but I don't actually understand who should control the objects' lifetime. I should explain this with an example: Let's say, another function calls widget->clear();. I don't know what happens beneath this call but I do think that memory allocated for item1 and item2 doesn't get disposed here, because their ownage wasn't actually transfered. And, bang, we have a memory leak. The question is the following - does Qt have something to offer for this kind of situation? I could use boost::shared_ptr or any other smart pointer and write something like shared_ptr<QTreeWidgetItem> ptr(new QTreeWidgetItem(...)); items.append(ptr.get()); but I don't know if the Qt itself would try to make explicit delete calls on my pointers (which would be disastrous since I state them as shared_ptr-managed). How would you solve this problem? Maybe everything is evident and I miss something really simple?

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  • Can't modify XNA Vector components

    - by Matt H
    I have a class called Sprite, and ballSprite is an instance of that class. Sprite has a Vector2 property called Position. I'm trying to increment the Vector's X component like so: ballSprite.Position.X++; but it causes this error: Cannot modify the return value of 'WindowsGame1.Sprite.Position' because it is not a variable Is it not possible to set components like this? The tooltip for the X and Y fields says "Get or set ..." so I can't see why this isn't working.

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  • Normal vector of a face loaded from an FBX model during collision?

    - by Corey Ogburn
    I'm loading a simple 6 sided cube from a UV-mapped FBX model and I'm using a BoundingBox to test for collisions. Once I determine there's a collision, I want to use the normal vector of the collided surface to correct the movement of whatever collided with the cube. I suppose this is a two-part question: 1) How can I determine which face of the cube was collided with in a collision? 2) How can I get the normal vector of that surface?

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  • My datacenter is unable to add PTR/rDNS record, then how can I prevent the mail outgoing from going to spam folder?

    - by gilzero
    I am having problem that mail sent out from my server all goes to recipient's spam folder. I am running Drupal sites on Linux server. CentOS w/ cPanel. Our users cannot receive email as the mail went to the spam folder. (such as registration email, contact form email) I was advised that I need to have PTR/rDNS record added for my host. I then contact my datacenter to add PTR/rDNS thing, unfortunately, the datacenter said they are unable to do it. So what can I do? Any other ways I can fix the problem? Thank you!

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  • Programmatically creating vector arrows in KML

    - by mettadore
    Does anyone have any practical examples of programmatically drawing icons as vectors in KML? Specifically, I have data with a magnitude and an azimuth at given coordinates, and I would like to have icons (or another graphical element) generated based on these values. Some thoughts on how I might approach it: Image directory (a brute force way): Make an image director of 360 different image files (probably batch rotate a single image) each pointing in a cooresponding azimuth. I've seen things like "Excel to KML," but am looking for code that I can use within a program, rather than a web utility. Issue: Arrow does not contain magnitude context, so that would have to be a label. I'd rather dynamically lengthen the arrow. Line creation in KML: Perhaps create a formula that creates a line with the origin at the coordinate points, with the length of the line proportional to the magnitute, and angled according to azimuth. There would then be two more lines, perhaps 30 degrees or so extending from the end of the previous line to make the arrow head. Issues: Not a separate image icon, so not sure how it would work in KML. Also not sure how easy it would be to generate this algorithm. Separate image generation: Perhaps create a PHP file that uses imagemagick or something similar to dynamically generate a .png file in a similar method to the above, and then link to the icon using the URI "domain.tld/imagegen.php?magnitude=magvalue&azimuth=azmvalue". Issue: Still have the problem of actually writing the algorithm for image generation. So, the question: has anyone else come up with solutions for programmatic vector (rather than merely arrow) generation?

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  • AndEngine VS Android's Canvas VS OpenGLES - For rendering a 2D indoor vector map

    - by Orchestrator
    This is a big issue for me I'm trying to figure out for a long time already. I'm working on an application that should include a 2D vector indoor map in it. The map will be drawn out from an .svg file that will specify all the data of the lines, curved lines (path) and rectangles that should be drawn. My main requirement from the map are Support touch events to detect where exactly the finger is touching. Great image quality especially when considering the drawings of curved and diagonal lines (anti-aliasing) Optional but very nice to have - Built in ability to zoom, pan and rotate. So far I tried AndEngine and Android's canvas. With AndEngine I had troubles with implementing anti-aliasing for rendering smooth diagonal lines or drawing curved lines, and as far as I understand, this is not an easy thing to implement in AndEngine. Though I have to mention that AndEngine's ability to zoom in and pan with the camera instead of modifying the objects on the screen was really nice to have. I also had some little experience with the built in Android's Canvas, mainly with viewing simple bitmaps, but I'm not sure if it supports all of these things, and especially if it would provide smooth results. Last but no least, there's the option of just plain OpenGLES 1 or 2, that as far as I understand, with enough work should be able to support all the features I require. However it seems like something that would be hard to implement. And I've never programmed in OpenGL or anything like it, but I'm willing very much to learn. To sum it all up, I need a platform that would provide me with the ability to do the 3 things I mentioned before, but also very important - To allow me to implement this feature as fast as possible. Any kind of answer or suggestion would be very much welcomed as I'm very eager to solve this problem! Thanks!

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  • Converting Single dimensional vector or array to two dimension in Matlab

    - by pac
    Well I do not know if I used the exact term. I tried to find an answer on the net. Here is what i need: I have a vector a = 1 4 7 2 5 8 3 6 9 If I do a(4) the value is 4. So it is reading first column top to buttom then continuing to next .... I don't know why. However, What I need is to call it using two indices. As row and column: a(3,2)= 4 or even better if i can call it in the following way: a{3}(2)=4 What is this process really called (want to learn) and how to perform in matlab. I thought of a loop. Is there a built in function Thanks a lot Check this: a = 18 18 16 18 18 18 16 0 0 0 16 16 18 0 18 16 0 18 18 16 18 0 18 18 0 16 0 0 0 18 18 0 18 18 16 0 16 0 18 18 >> a(4) ans = 18 >> a(5) ans = 18 >> a(10) ans = 18 I tried reshape. it is reshaping not converting into 2 indeces

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  • Caching vector addition over changing collections

    - by DRMacIver
    I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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  • Fill lower matrix with vector by row, not column

    - by mhermans
    I am trying to read in a variance-covariance matrix written out by LISREL in the following format in a plain text, whitespace separated file: 0.23675E+01 0.86752E+00 0.28675E+01 -0.36190E+00 -0.36190E+00 0.25381E+01 -0.32571E+00 -0.32571E+00 0.84425E+00 0.25598E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.21120E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.91200E+00 0.21120E+01 This is actually a lower diagonal matrix (including diagonal): 0.23675E+01 0.86752E+00 0.28675E+01 -0.36190E+00 -0.36190E+00 0.25381E+01 -0.32571E+00 -0.32571E+00 0.84425E+00 0.25598E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.21120E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.91200E+00 0.21120E+01 I can read in the values correctly with scan() or read.table(fill=T). I am however not able to correctly store the read-in vector in a matrix. The following code S <- diag(6) S[lower.tri(S,diag=T)] <- d fills the lower matrix by column, while it should fill it by row. Using matrix() does allow for the option byrow=TRUE, but this will fill in the whole matrix, not just the lower half (with diagonal). Is it possible to have both: only fill the lower matrix (with diagonal) and do it by row? (separate issue I'm having: LISREL uses 'D+01' while R only recognises 'E+01' for scientific notation. Can you change this in R to accept also 'D'?)

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  • Dynamic Array of Objects Sans Vector Class

    - by Connor Black
    I am doing a homework assignment for my summer OO class and we need to write two classes. One is called Sale and the other is called Register. I've written my Sale class; here's the .h file: enum ItemType {BOOK, DVD, SOFTWARE, CREDIT}; class Sale { public: Sale(); // default constructor, // sets numerical member data to 0 void MakeSale(ItemType x, double amt); ItemType Item(); // Returns the type of item in the sale double Price(); // Returns the price of the sale double Tax(); // Returns the amount of tax on the sale double Total(); // Returns the total price of the sale void Display(); // outputs sale info private: double price; // price of item or amount of credit double tax; // amount of sales tax double total; // final price once tax is added in. ItemType item; // transaction type }; For the Register class we need to include a dynamic array of Sale objects in our member data. We cannot use the vector class. How is this done? Here's my 'Register' '.h' class Register{ public: Register(int ident, int amount); ~Register(); int GetID(){return identification;} int GetAmount(){return amountMoney;} void RingUpSale(ItemType item, int basePrice); void ShowLast(); void ShowAll(); void Cancel(); int SalesTax(int n); private: int identification; int amountMoney; };

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  • Convert binary unsigned vector to dec list

    - by Juan
    This code convert a unsigned long vector variable cR1 to NB_ERRORS numbers (in 'a' variable I print these numbers). for (l = 0; l < NB_ERRORS; ++l) { k = (l * EXT_DEGREE) / BIT_SIZE_OF_LONG; j = (l * EXT_DEGREE) % BIT_SIZE_OF_LONG; a = cR1[k] >> j; if(j + EXT_DEGREE > BIT_SIZE_OF_LONG) a ^= cR1[k + 1] << (BIT_SIZE_OF_LONG - j); a &= ((1 << EXT_DEGREE) - 1); printf("\na=%d\n",a); } For example I am have a cR1 with two elements that follow: 0,0,1,1,0,1,0,0,0,0,1,0,0,1,1,1,1,1,0,0,1,1,1,1,0,0,0,1,1,0,0,0,1,0,1,1,0,0,1,0,1,1,1,0,0,1,0,0,1,0,1,0,1,1,1,0,1,0,0,1,1,1,1,0, executing that code I get (44), (228, (243), (24), (77), (39), (117), (121). This code convert from right to left, I want modify to convert from right to left, Where I will be able to modify this? pdta: In the example case EXT_DEGREE = 8, BIT_SIZE_OF_LONG = 32

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  • I get the following error when i open any progaram in vi please help me

    - by Adithya Chakilam
    E325: ATTENTION Found a swap file by the name ".ptr.c.swp" owned by: honey dated: Sat Oct 26 12:49:38 2013 file name: ~honey/ptr.c modified: YES user name: honey host name: honey-desktop process ID: 2542 While opening file "ptr.c" dated: Sun Nov 3 09:05:49 2013 NEWER than swap file! (1) Another program may be editing the same file. If this is the case, be careful not to end up with two different instances of the same file when making changes. Quit, or continue with caution. (2) An edit session for this file crashed. If this is the case, use ":recover" or "vim -r ptr.c" to recover the changes (see ":help recovery"). If you did this already, delete the swap file ".ptr.c.swp" to avoid this message. "ptr.c" 9L, 136C Press ENTER or type command to continue

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  • Hundreds of unknown entries in Linux logwatch

    - by Saif Bechan
    I have a dedicated server which runs centos. Today i got an email from loginwatch on my server with hundreds of lines of 'errors'. I don't really know what they are becasue i am fairly new at this. The lines are in a few sections, I will display the first 10 of all of them, i hope someone can help me fix these problems. --------------------- Named Begin ------------------------ **Unmatched Entries** client 216.146.46.136 notify question section contains no SOA: 8 Time(s) client 92.114.98.10 query (cache) 'adobe.com/A/IN' denied: 4 Time(s) network unreachable resolving '11.254.75.75.in-addr.arpa/PTR/IN': 2001:7fd::1#53: 1 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:13c7:7002:3000::11#53: 1 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:500:13::c7d4:35#53: 1 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:500:2e::1#53: 2 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:610:240:0:53::193#53: 1 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:610:240:0:53::3#53: 1 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:660:3006:1::1:1#53: 1 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:6b0:7::2#53: 1 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:dc0:1:0:4777::140#53: 1 Time(s) network unreachable resolving '136.176.97.93.in-addr.arpa/PTR/IN': 2001:dc0:2001:a:4608::59#53: 1 Time(s) network unreachable resolving '146.250.19.67.in-addr.arpa/PTR/IN': 2001:5a0:10::2#53: 1 Time(s) network unreachable resolving '149.207.106.87.in-addr.arpa/PTR/IN': 2001:7fd::1#53: 1 Time(s) network unreachable resolving '178.62.24.195.in-addr.arpa/PTR/IN': 2001:7fd::1#53: 1 Time(s) this goes on for hundreds of lines with all different domain names. --------------------- pam_unix Begin ------------------------ Failed logins from: 78.86.126.211 (78-86-126-211.zone2.bethere.co.uk): 111 times 93.97.176.136 (93-97-176-136.dsl.cnl.uk.net): 113 times 121.14.145.32: 136 times 190.152.69.5: 248 times 209.160.72.15: 572 times 210.26.48.35: 2 times 212.235.111.224 (DSL212-235-111-224.bb.netvision.net.il): 140 times 218.206.25.29: 140 times Illegal users from: 78.86.126.211 (78-86-126-211.zone2.bethere.co.uk): 2665 times 93.97.176.136 (93-97-176-136.dsl.cnl.uk.net): 2539 times 121.14.145.32: 116 times 190.152.69.5: 34 times 209.160.72.15: 324 times 218.206.25.29: 8051 times proftpd: Unknown Entries: session opened for user cent_ftp by (uid=0): 15 Time(s) session closed for user cent_ftp: 14 Time(s) sshd: Authentication Failures: unknown (218.206.25.29): 8051 Time(s) unknown (78-86-126-211.zone2.bethere.co.uk): 2665 Time(s) unknown (93.97.176.136): 2539 Time(s) root (209.160.72.15): 558 Time(s) unknown (209.160.72.15): 324 Time(s) root (190.152.69.5): 246 Time(s) unknown (121.14.145.32): 116 Time(s) root (121.14.145.32): 106 Time(s) root (dsl212-235-111-224.bb.netvision.net.il): 70 Time(s) root (93.97.176.136): 44 Time(s) root (78-86-126-211.zone2.bethere.co.uk): 37 Time(s) unknown (190.152.69.5): 34 Time(s) mysql (121.14.145.32): 30 Time(s) nobody (218.206.25.29): 26 Time(s) mail (218.206.25.29): 24 Time(s) news (218.206.25.29): 24 Time(s) root (218.206.25.29): 24 Time(s) --------------------- SSHD Begin ------------------------ **Unmatched Entries** pam_succeed_if(sshd:auth): error retrieving information about user tavi : 2 time(s) pam_succeed_if(sshd:auth): error retrieving information about user pam : 2 time(s) pam_succeed_if(sshd:auth): error retrieving information about user konchog : 1 time(s) pam_succeed_if(sshd:auth): error retrieving information about user stavrum : 2 time(s) pam_succeed_if(sshd:auth): error retrieving information about user rachel : 1 time(s) pam_succeed_if(sshd:auth): error retrieving information about user affiliates : 24 time(s) pam_succeed_if(sshd:auth): error retrieving information about user nen : 1 time(s) pam_succeed_if(sshd:auth): error retrieving information about user cobra : 1 time(s) pam_succeed_if(sshd:auth): error retrieving information about user pass : 7 time(s) pam_succeed_if(sshd:auth): error retrieving information about user hacer : 1 time(s) pam_succeed_if(sshd:auth): error retrieving information about user chung : 1 time(s) pam_succeed_if(sshd:auth): error retrieving information about user zainee : 1 time(s) pam_succeed_if(sshd:auth): error retrieving information about user radu : 2 time(s) pam_succeed_if(sshd:auth): error retrieving information about user alka : 4 time(s) pam_succeed_if(sshd:auth): error retrieving information about user albert : 5 time(s) pam_succeed_if(sshd:auth): error retrieving information about user turcia : 2 time(s) pam_succeed_if(sshd:auth): error retrieving information about user cordell : 2 time(s) pam_succeed_if(sshd:auth): error retrieving information about user silver : 2 time(s) pam_succeed_if(sshd:auth): error retrieving information about user dragon : 3 time(s) If someone wants to see the whole log i can upload it somewhere. Am i being hacked, what is this all?? I hope someone can help me, this does not look good at all.

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  • WPF 3D extrude "a bitmap"

    - by Bgnt44
    Hi, I'm looking for a way to simulate a projector in wpf 3D : i've these "in" parameters : beam shape : a black and white bitmap file beam size ( ex : 30 °) beam color beam intensity ( dimmer ) projector position (x,y,z) beam position (pan(x),tilt(y) relative to projector) First i was thinking of using light object but it seem that wpf can't do that So, now i think that i can make for each projector a polygon from my bitmap... First i need to convert the black and white bitmap to vector. Only Simple shape ( bubble, line,dot,cross ...) Is there any WPF way to do that ? Or maybe a external program file (freeware); then i need to build the polygon, with the shape of the converted bitmap , color , size , orientation in parameter. i don't know how can i defined the lenght of the beam , and if it can be infiny ... To show the beam result, i think of making a room ( floor , wall ...) and beam will end to these wall... i don't care of real light render ( dispersion ...) but the scene render has to be real time and at least 15 times / second (with probably from one to 100 projectors at the same time), information about position, angle,shape,color will be sent for each render... Well so, i need sample for that, i guess that all of these things could be useful for other people If you have sample code : Convert Bitmap to vector Extrude vectors from one point with a angle parameter until collision of a wall Set x,y position of the beam depend of the projector position Set Alpha intensity of the beam, color Maybe i'm totally wrong and WPF is not ready for that , so advise me about other way ( xna,d3D ) with sample of course ;-) Thanks you

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  • Diffie-Hellman -- Primitive root mod n -- cryptography question.

    - by somewhat confused
    In the below snippet, please explain starting with the first "for" loop what is happening and why. Why is 0 added, why is 1 added in the second loop. What is going on in the "if" statement under bigi. Finally explain the modPow method. Thank you in advance for meaningful replies. public static boolean isPrimitive(BigInteger m, BigInteger n) { BigInteger bigi, vectorint; Vector<BigInteger> v = new Vector<BigInteger>(m.intValue()); int i; for (i=0;i<m.intValue();i++) v.add(new BigInteger("0")); for (i=1;i<m.intValue();i++) { bigi = new BigInteger("" + i); if (m.gcd(bigi).intValue() == 1) v.setElementAt(new BigInteger("1"), n.modPow(bigi,m).intValue()); } for (i=0;i<m.intValue();i++) { bigi = new BigInteger("" + i); if (m.gcd(bigi).intValue() == 1) { vectorint = v.elementAt(bigi.intValue()); if ( vectorint.intValue() == 0) i = m.intValue() + 1; } } if (i == m.intValue() + 2) return false; else return true; }

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  • With Go, how to append unknown number of byte into a vector and get a slice of bytes?

    - by Stephen Hsu
    I'm trying to encode a large number to a list of bytes(uint8 in Go). The number of bytes is unknown, so I'd like to use vector. But Go doesn't provide vector of byte, what can I do? And is it possible to get a slice of such a byte vector? I intends to implement data compression. Instead of store small and large number with the same number of bytes, I'm implements a variable bytes that uses less bytes with small number and more bytes with large number. My code can not compile, invalid type assertion: 1 package main 2 3 import ( 4 //"fmt" 5 "container/vector" 6 ) 7 8 func vbEncodeNumber(n uint) []byte{ 9 bytes := new(vector.Vector) 10 for { 11 bytes.Push(n % 128) 12 if n < 128 { 13 break 14 } 15 n /= 128 16 } 17 bytes.Set(bytes.Len()-1, bytes.Last().(byte)+byte(128)) 18 return bytes.Data().([]byte) // <- 19 } 20 21 func main() { vbEncodeNumber(10000) } I wish to writes a lot of such code into binary file, so I wish the func can return byte array. I haven't find a code example on vector.

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  • error C2512 in precompiled header file?

    - by SoloMael
    I'm having a ridiculously strange problem. When I try to run the program below, there's an error message that says: "error C2512: 'Record' : no appropriate default constructor available". And when I double-click it, it directs me to a precompiled read-only header file named "xmemory0". Do they expect me to change a read-only file? Here's the segment of code in the file it directs me to: void construct(_Ty *_Ptr) { // default construct object at _Ptr ::new ((void *)_Ptr) _Ty(); // directs me to this line } Here's the program: #include <iostream> #include <vector> #include <string> using namespace std; const int NG = 4; // number of scores struct Record { string name; // student name int scores[NG]; double average; // Calculate the average // when the scores are known Record(int s[], double a) { double sum = 0; for(int count = 0; count != NG; count++) { scores[count] = s[count]; sum += scores[count]; } average = a; average = sum / NG; } }; int main() { // Names of the class string names[] = {"Amy Adams", "Bob Barr", "Carla Carr", "Dan Dobbs", "Elena Evans"}; // exam scores according to each student int exams[][NG]= { {98, 87, 93, 88}, {78, 86, 82, 91}, {66, 71, 85, 94}, {72, 63, 77, 69}, {91, 83, 76, 60}}; vector<Record> records(5); return 0; }

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  • gluLookAt vectors and FPS-style camera

    - by Kevin Pamplona
    I am attempting to implemented an FPS-style camera by updating three vectors: EYE, DIR, UP. These vectors are the same that are used by gluLookAt (since gluLookAt is specified by the position of the camera, the direction it is looking at, and an up vector). I have already implemented the left-right and up-down strafing movements, but I'm having a lot of trouble understanding the math behind making the camera look-around while remaining stationary. In this case, the EYE vector remains the same, while I must update DIR and UP. Below is the code I tried, but it doesn't seem to work properly. Any suggestions? Thanks. void Transform::left(float degrees, vec3& dir, vec3& up) { vec3 axis; axis = glm::normalize(up); mat3 R = rotate(-degrees, axis); dir = R*dir; dir = R*up; }; void Transform::up(float degrees, vec3& dir, vec3& up) { vec3 axis; axis=glm::normalize(glm::cross(dir,up)); mat3 R = rotate(-degrees, axis); dir = R*dir-; up = R*up; };

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  • How to animate a path like it's being drawn, dot by dot? (Raphael.js)

    - by Anton
    How to animate a vector path like it's being drawn by hand? In other words, slowly show the path pixel by pixel. I'm using Raphaël.js, but if your answer is not library specific—like maybe there's some general programming pattern for doing that kind of thing (I'm fairly new to vector animation)—it's welcome! Update I know it's easy to do with straight paths, as easy as an example on that page:: path("M114 253").animate({path: "M114 253 L 234 253"}); But try to change code on that page, say, this way:: path("M114 26").animate({path: "M114 26 C 24 23 234 253 234 253"}); And you'll see what I mean. Path is certainly animated from it initial state (point "M114 26") to the end state (curve "C 24 23 234 253 234 253" starting on point "M114 26"), but not in a way specified in question, not like it's being drawn. (Sorry for not making clear from the start that I don't mean animating straight lines.) I don't see how animateAlong can do that either. It can animate an object along a path, and how can I make this path to gradually show itself while object is being animated along it?

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  • Boost shared_ptr use_count function

    - by photo_tom
    My application problem is the following - I have a large structure foo. Because these are large and for memory management reasons, we do not wish to delete them when processing on the data is complete. We are storing them in std::vector<boost::shared_ptr<foo>>. My question is related to knowing when all processing is complete. First decision is that we do not want any of the other application code to mark a complete flag in the structure because there are multiple execution paths in the program and we cannot predict which one is the last. So in our implementation, once processing is complete, we delete all copies of boost::shared_ptr<foo>> except for the one in the vector. This will drop the reference counter in the shared_ptr to 1. Is it practical to use shared_ptr.use_count() to see if it is equal to 1 to know when all other parts of my app are done with the data. One additional reason I'm asking the question is that the boost documentation on the shared pointer shared_ptr recommends not using "use_count" for production code.

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  • Incorrect results for frustum cull

    - by DeadMG
    Previously, I had a problem with my frustum culling producing too optimistic results- that is, including many objects that were not in the view volume. Now I have refactored that code and produced a cull that should be accurate to the actual frustum, instead of an axis-aligned box approximation. The problem is that now it never returns anything to be in the view volume. As the mathematical support library I'm using does not provide plane support functions, I had to code much of this functionality myself, and I'm not really the mathematical type, so it's likely that I've made some silly error somewhere. As follows is the relevant code: class Plane { public: Plane() { r0 = Math::Vector(0,0,0); normal = Math::Vector(0,1,0); } Plane(Math::Vector p1, Math::Vector p2, Math::Vector p3) { r0 = p1; normal = Math::Cross((p2 - p1), (p3 - p1)); } Math::Vector r0; Math::Vector normal; }; This class represents one plane as a point and a normal vector. class Frustum { public: Frustum( const std::array<Math::Vector, 8>& points ) { planes[0] = Plane(points[0], points[1], points[2]); planes[1] = Plane(points[4], points[5], points[6]); planes[2] = Plane(points[0], points[1], points[4]); planes[3] = Plane(points[2], points[3], points[6]); planes[4] = Plane(points[0], points[2], points[4]); planes[5] = Plane(points[1], points[3], points[5]); } Plane planes[6]; }; The points are passed in order where (the inverse of) each bit of the index of each point indicates whether it's the left, top, and back of the frustum, respectively. As such, I just picked any three points where they all shared one bit in common to define the planes. My intersection test is as follows (based on this): bool Intersects(Math::AABB lhs, const Frustum& rhs) const { for(int i = 0; i < 6; i++) { Math::Vector pvertex = lhs.TopRightFurthest; Math::Vector nvertex = lhs.BottomLeftClosest; if (rhs.planes[i].normal.x <= -0.0f) { std::swap(pvertex.x, nvertex.x); } if (rhs.planes[i].normal.y <= -0.0f) { std::swap(pvertex.y, nvertex.y); } if (rhs.planes[i].normal.z <= -0.0f) { std::swap(pvertex.z, nvertex.z); } if (Math::Dot(rhs.planes[i].r0, nvertex) < 0.0f) { return false; } } return true; } Also of note is that because I'm using a left-handed co-ordinate system, I wrote my Cross function to return the negative of the formula given on Wikipedia. Any suggestions as to where I've made a mistake?

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  • Why is shrink_to_fit non-binding?

    - by Roger Pate
    The C++0x FCD states in 23.3.6.2 vector capacity: void shrink_to_fit(); Remarks: shrink_to_fit is a non-binding request to reduce capacity() to size(). [Note: The request is non-binding to allow latitude for implementation-specific optimizations. —end note] Why is it non-binding, and what optimizations are intended to be allowed?

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