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  • Using memcpy in the STL

    - by wowus
    Why does C++'s vector class call copy constructors? Why doesn't it just memcpy the underlying data? Wouldn't that be a lot faster, and remove half of the need for move semantics? I can't imagine a use case where this would be worse, but then again, maybe it's just because I'm being quite unimaginative.

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  • pure as3 benefits to compiling with flex4 instead of flex3?

    - by jedierikb
    If I have a pure as3 project that I have been compiling with flex3 from mxmlc, is there any reason to switch to using the mxmlc with flex4? I can use all of the flash 10 language features like Vector, 3D, etc., so that is not a reason to switch (or is there something I can't do?). But maybe there is a performance boost? Or is the exact same compiling tool and the flex code base is the only difference?

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  • Boost::Serialization Mpi Sending array of user defined types

    - by Noman Javed
    I want to send my Array class using boost Mpi template class Array { private: int size; T* data; public: // constructors + other stuff }; Here T can be any built in type or user defined type. Suppose I have a class complex struct complex { std::vector real_imag; // contain two elements }; So the question is how can I send Array using Boost::Mpi + serialization. Thanks in anticipation Regards Noman

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  • conflicting declaration when filling a static std::map class member variable

    - by Max
    I have a class with a static std::map member variable that maps chars to a custom type Terrain. I'm attempting to fill this map in the class's implementation file, but I get several errors. Here's my header file: #ifndef LEVEL_HPP #define LEVEL_HPP #include <bitset> #include <list> #include <map> #include <string> #include <vector> #include "libtcod.hpp" namespace yarl { namespace level { class Terrain { // Member Variables private: std::bitset<5> flags; // Member Functions public: explicit Terrain(const std::string& flg) : flags(flg) {} (...) }; class Level { private: static std::map<char, Terrain> terrainTypes; (...) }; } } #endif and here's my implementation file: #include <bitset> #include <list> #include <map> #include <string> #include <vector> #include "Level.hpp" #include "libtcod.hpp" using namespace std; namespace yarl { namespace level { /* fill Level::terrainTypes */ map<char,Terrain> Level::terrainTypes['.'] = Terrain("00001"); // clear map<char,Terrain> Level::terrainTypes[','] = Terrain("00001"); // clear map<char,Terrain> Level::terrainTypes['\''] = Terrain("00001"); // clear map<char,Terrain> Level::terrainTypes['`'] = Terrain("00001"); // clear map<char,Terrain> Level::terrainTypes[178] = Terrain("11111"); // wall (...) } } I'm using g++, and the errors I get are src/Level.cpp:15: error: conflicting declaration ‘std::map, std::allocator yarl::level::Level::terrainTypes [46]’ src/Level.hpp:104: error: ‘yarl::level::Level::terrainTypes’ has a previous declaration as ‘std::map, std::allocator yarl::level::Level::terrainTypes’ src/Level.cpp:15: error: declaration of ‘std::map, std::allocator yarl::level::Level::terrainTypes’ outside of class is not definition src/Level.cpp:15: error: conversion from ‘yarl::level::Terrain’ to non-scalar type ‘std::map, std::allocator ’ requested src/Level.cpp:15: error: ‘yarl::level::Level::terrainTypes’ cannot be initialized by a non-constant expression when being declared I get a set of these for each map assignment line in the implementation file. Anyone see what I'm doing wrong? Thanks for your help.

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  • Converting integer to a bit representation

    - by bobber205
    How can I convert a integer to its bit representation. I want to take an integer and return a vector that has contains 1's and 0's of the integer's bit representation. I'm having a heck of a time trying to do this myself so I thought I would ask to see if there was a built in library function that could help. Thanks!

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  • getSymbols and using lapply, Cl, and merge to extract close prices

    - by algotr8der
    I've been messing around with this for some time. I recently started using the quantmod package to perform analytics on stock prices. I have a ticker vector that looks like the following: > tickers [1] "SPY" "DIA" "IWM" "SMH" "OIH" "XLY" "XLP" "XLE" "XLI" "XLB" "XLK" "XLU" "XLV" [14] "QQQ" > str(tickers) chr [1:14] "SPY" "DIA" "IWM" "SMH" "OIH" "XLY" "XLP" "XLE" ... I wrote a function called myX to use in a lapply call to save prices for every stock in the vector tickers. It has the following code: myX <- function(tickers, start, end) { require(quantmod) getSymbols(tickers, from=start, to=end) } I call lapply by itself library(quantmod) lapply(tickers,myX,start="2001-03-01", end="2011-03-11") > lapply(tickers,myX,start="2001-03-01", end="2011-03-11") [[1]] [1] "SPY" [[2]] [1] "DIA" [[3]] [1] "IWM" [[4]] [1] "SMH" [[5]] [1] "OIH" [[6]] [1] "XLY" [[7]] [1] "XLP" [[8]] [1] "XLE" [[9]] [1] "XLI" [[10]] [1] "XLB" [[11]] [1] "XLK" [[12]] [1] "XLU" [[13]] [1] "XLV" [[14]] [1] "QQQ" That works fine. Now I want to merge the Close prices for every stock into an object that looks like # BCSI.Close WBSN.Close NTAP.Close FFIV.Close SU.Close # 2011-01-03 30.50 20.36 57.41 134.33 38.82 # 2011-01-04 30.24 19.82 57.38 132.07 38.03 # 2011-01-05 31.36 19.90 57.87 137.29 38.40 # 2011-01-06 32.04 19.79 57.49 138.07 37.23 # 2011-01-07 31.95 19.77 57.20 138.35 37.30 # 2011-01-10 31.55 19.76 58.22 142.69 37.04 Someone recommended I try something like the following: ClosePrices <- do.call(merge, lapply(tickers, function(x) Cl(get(x)))) However I tried various combinations of this without any success. First I tried just calling lapply with Cl(x) >lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl(myX))) > lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl(x))) Error: unexpected symbol in "lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl" > > lapply(tickers,myX(x),start="2001-03-01", end="2011-03-11") Cl(x))) Error: unexpected symbol in "lapply(tickers,myX(x),start="2001-03-01", end="2011-03-11") Cl" > > lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl(x) Error: unexpected symbol in "lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl" > lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl(x)) Error: unexpected symbol in "lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl" > Any guidance would be kindly appreciated.

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  • iPhone: Tracking/Identifying individual touches

    - by FlorianZ
    I have a quick question regarding tracking touches on the iPhone and I seem to not be able to come to a conclusion on this, so any suggestions / ideas are greatly appreciated: I want to be able to track and identify touches on the iphone, ie. basically every touch has a starting position and a current/moved position. Touches are stored in a std::vector and they shall be removed from the container, once they ended. Their position shall be updated once they move, but I still want to keep track of where they initially started (gesture recognition). I am getting the touches from [event allTouches], thing is, the NSSet is unsorted and I seem not to be able to identify the touches that are already stored in the std::vector and refer to the touches in the NSSet (so I know which ones ended and shall be removed, or have been moved, etc.) Here is my code, which works perfectly with only one finger on the touch screen, of course, but with more than one, I do get unpredictable results... - (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event { [self handleTouches:[event allTouches]]; } - (void) touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event { [self handleTouches:[event allTouches]]; } - (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event { [self handleTouches:[event allTouches]]; } - (void) touchesCancelled:(NSSet*)touches withEvent:(UIEvent*)event { [self handleTouches:[event allTouches]]; } - (void) handleTouches:(NSSet*)allTouches { for(int i = 0; i < (int)[allTouches count]; ++i) { UITouch* touch = [[allTouches allObjects] objectAtIndex:i]; NSTimeInterval timestamp = [touch timestamp]; CGPoint currentLocation = [touch locationInView:self]; CGPoint previousLocation = [touch previousLocationInView:self]; if([touch phase] == UITouchPhaseBegan) { Finger finger; finger.start.x = currentLocation.x; finger.start.y = currentLocation.y; finger.end = finger.start; finger.hasMoved = false; finger.hasEnded = false; touchScreen->AddFinger(finger); } else if([touch phase] == UITouchPhaseEnded || [touch phase] == UITouchPhaseCancelled) { Finger& finger = touchScreen->GetFingerHandle(i); finger.hasEnded = true; } else if([touch phase] == UITouchPhaseMoved) { Finger& finger = touchScreen->GetFingerHandle(i); finger.end.x = currentLocation.x; finger.end.y = currentLocation.y; finger.hasMoved = true; } } touchScreen->RemoveEnded(); } Thanks!

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  • Why does std queue not define a swap method specialisation

    - by Jamie Cook
    I've read that all stl containers provide a specialisation of the swap algorithm so as to avoid calling the copy constructor and two assignment operations that the default method uses. However, when I thought it would be nice to use a queue in some code I was working on I noticed that (unlike vector and deque) queue doesn't provide this method? I just decided to use a deque instead of a queue, but still I'm interested to know why this is?

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  • Version of STL optimized for compile time?

    - by anon
    Hi! I'm looking for a variant of the STL (it's okay if it doesn't have all the functionality) that's optimized for short compile times -- I get bothered by long compile times that delay my compile-debug-edit cycle. I'm mainly interested in the containers of the STL: vector/map, and not so much the algorithms. Thanks!

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  • When should a uniform be used in shader programming?

    - by Phineas
    In a vertex shader, I calculate a vector using only uniforms. Therefore, the outcome of this calculation is the same for all instantiations of the vertex shader. Should I just do this calculation on the CPU and upload it as a uniform? What if I have ten such calculations? If I upload a lot of uniforms in this way, does CPU-GPU communication ever get so slow that recomputing such values in the vertex shader is actually faster?

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  • JAVA - Strange problem (probably thread problem) with JTable & Model

    - by Stefanos Kargas
    I am using 2 Tables (JTable) with their DefaultTableModels. The first table is already populated. The second table is populated for each row of the first table (using an SQL Query). My purpose is to export every line of the first table with it's respective lines of the second in an Excel File. I am doing it with a for (for each line of 1st table), in which I write a line of the 1st table in the Excel File, then I populate the 2nd table (for this line of 1st Table), I get every line from the Table (from it's Model actually) and put it in the Excel File under the current line of 1st table. This means that if I have n lines in first table I will clear and populate again the second table n times. All this code is called in a seperate thread. THE PROBLEM IS: Everything works perfectly fine ecxept that I am getting some exceptions. The strange thing is that I'm not getting anything false in my result. The Excel file is perfect. Some of the lines of the exceptions are: Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 0 = 0 at java.util.Vector.elementAt(Vector.java:427) at javax.swing.table.DefaultTableModel.getValueAt(DefaultTableModel.java:632) at javax.swing.JComponent.paint(JComponent.java:1017) at javax.swing.RepaintManager.paint(RepaintManager.java:1220) at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:803) I am assuming that the problem lies in the fact that the second table needs some more time to be populated before I try to get any data from it. That's why I see RepaintManager and paintDirtyRegions in my exceptions. Another thing I did is that I ran my program in debug mode and I put a breakpoint after each population of the 2nd table. Then I pressed F5 to continue for each population of 2nd table and no exception appeared. The program came to it's end without any exceptions. This is another important fact that tells me that maybe in this case I gave the table enough time to be populated. Of course you will ask me: If your program works fine, why do you care about the exceptions? I care for avoiding any future problems and I care to have a better understanding of Java and Java GUI and threads. Why do you depend on a GUI component (and it's model) to get your information and why don't you recreate the resultset that populates your tables using an SQL Query and get your info from the resultset? That would be the best and the right way. The fact is that I have the tables code ready and it was easier for me to just get the info from them. But the right way would be to get everything direct from database. Anyway what I did brought out my question, and answering it would help me understand more things about java. So I posted it.

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  • C++: Unknown pointer size when forward declaring (error C2036)

    - by Rosarch
    In a header file, I have forward declared two members of a namespace: namespace Foo { struct Odp typedef std::vector<Odp> ODPVEC; }; class Bar { public: Foo::ODPVEC baz; // C2036 }; The error generated by the compiler is: error C2036: 'Foo::Odp *': unknown size I'm guessing this is an issue with forward declaring Odp. How can I get around this?

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  • Array performance question

    - by Konrad
    I am very familiar with STL vector (and other container) performance guarantees, however I can't seem to find anything concrete about plain arrays. Are pointer arithmetic and [] methods constant or linear time?

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  • Specifying column names from a list in the data.frame command.

    - by MW Frost
    I have a list called cols with column names in it: cols <- c('Column1','Column2','Column3') I'd like to reproduce this command, but with a call to the list: data.frame(Column1=rnorm(10)) Here's what happens when I try it: > data.frame(cols[1]=rnorm(10)) Error: unexpected '=' in "data.frame(I(cols[1])=" The same thing happens if I wrap cols[1] in I() or eval(). How can I feed that item from the vector into the data.frame() command?

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  • How can I make a resizable array in Java?

    - by Soren Johnson
    What is the best way to do a resizable array in Java? I tried using Vector, but that shifts all elements over by when when you do an insert, and I need an array that can grow but the elements stay in place. I'm sure there's a simple answer for this, but I still not quite sure.

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  • R: Select subset of dataframe by non-unique ids

    - by amarillion
    Suppose I have a dataframe like this one: df <- data.frame (id = c("a", "b", "a", "c", "e", "d", "e"), n=1:7) and a vector with ids like this one: v <- c("a", "b") How can I select the rows of the dataframe that match the ids in v? I can't use the id column for rownames because they are not unique.

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  • kill unsigned / signed comparison error

    - by anon
    In general, I want warnings of unsigned vs signed. However, in this particular case, I want it supressed; std::vector<Blah> blahs; for(int i = 0; i < blahs.size(); ++i) { ... I want to kill this comparison. Thanks! (using g++)

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  • C++ Virtual Constructor, without clone()

    - by Julien L.
    I want to perform "deep copies" of an STL container of pointers to polymorphic classes. I know about the Prototype design pattern, implemented by means of the Virtual Ctor Idiom, as explained in the C++ FAQ Lite, Item 20.8. It is simple and straightforward: struct ABC // Abstract Base Class { virtual ~ABC() {} virtual ABC * clone() = 0; }; struct D1 : public ABC { virtual D1 * clone() { return new D1( *this ); } // Covariant Return Type }; A deep copy is then: for( i = 0; i < oldVector.size(); ++i ) newVector.push_back( oldVector[i]->clone() ); Drawbacks As Andrei Alexandrescu states it: The clone() implementation must follow the same pattern in all derived classes; in spite of its repetitive structure, there is no reasonable way to automate defining the clone() member function (beyond macros, that is). Moreover, clients of ABC can possibly do something bad. (I mean, nothing prevents clients to do something bad, so, it will happen.) Better design? My question is: is there another way to make an abstract base class clonable without requiring derived classes to write clone-related code? (Helper class? Templates?) Following is my context. Hopefully, it will help understanding my question. I am designing a class hierarchy to perform operations on a class Image: struct ImgOp { virtual ~ImgOp() {} bool run( Image & ) = 0; }; Image operations are user-defined: clients of the class hierarchy will implement their own classes derived from ImgOp: struct CheckImageSize : public ImgOp { std::size_t w, h; bool run( Image &i ) { return w==i.width() && h==i.height(); } }; struct CheckImageResolution; struct RotateImage; ... Multiple operations can be performed sequentially on an image: bool do_operations( std::vector< ImgOp* > v, Image &i ) { std::for_each( v.begin(), v.end(), /* bind2nd(mem_fun(&ImgOp::run), i ...) don't remember syntax */ ); } int main( ... ) { std::vector< ImgOp* > v; v.push_back( new CheckImageSize ); v.push_back( new CheckImageResolution ); v.push_back( new RotateImage ); Image i; do_operations( v, i ); } If there are multiple images, the set can be split and shared over several threads. To ensure "thread-safety", each thread must have its own copy of all operation objects contained in v -- v becomes a prototype to be deep copied in each thread.

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  • gmail drawing send

    - by siran
    is there some online web app which would let me make a vector drawing, and give me the choice to write some text and send it through gmail ? for the magic to be complete, the web app would save my drawing as png (or whatever) and attach it to the sent email... i guess i would have to give the webapp my gmail account info so it can send it from my account...

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