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  • Convert string from getline into a number

    - by haskellguy
    I am trying to create a 2D array with vectors. I have a file that has for each line a set of numbers. So what I did I implemented a split function that every time I have a new number (separated by \t) it splits that and add it to the vector vector<double> &split(const string &s, char delim, vector<double> &elems) { stringstream ss(s); string item; while (getline(ss, item, delim)) { cout << item << endl; double number = atof(item.c_str()); cout << number; elems.push_back(number); } return elems; } vector<double> split(const string &s, char delim) { vector<double> elems; split(s, delim, elems); return elems; } After that I simply iterate through it. int main() { ifstream file("./data/file.txt"); string row; vector< vector<double> > matrix; int line_count = -1; while (getline(file, row)) { line_count++; if (line_count <= 4) continue; vector<double> cols = split(row, '\t'); matrix.push_back(cols); } ... } Now my issues is in this bit here: while (getline(ss, item, delim)) { cout << item << endl; double number = atof(item.c_str()); cout << number; Where item.c_str() is converted to a 0. Shouldn't that be still a string having the same value as item? It works on a separate example if I do straight from string to c_string, but when I use this getline I end up in this error situation, hints?

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  • how to fast compute distance between high dimension vectors

    - by chyojn
    assume there are three group of high dimension vectors: {a_1, a_2, ..., a_N}, {b_1, b_2, ... , b_N}, {c_1, c_2, ..., c_N}. each of my vector can be represented as: x = a_i + b_j + c_k, where 1 <=i, j, k <= N. then the vector is encoded as (i, j, k) wich is then can be decoded as x = a_i + b_j + c_k. my question is, if there are two vector: x = (i_1, j_1, k_1), y = (i_2, j_2, k_2), is there a method to compute the euclidian distance of these two vector without decode x and y.

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  • My IDE is showing "undeclared FileNotFoundException must be caught or thrown"

    - by Dan Czarnecki
    I am having the following issue above. I have tried actually putting a try-catch statement into the code as you will see below, but I can't get the compiler to get past that. import java.io.*; public class DirectoryStatistics extends DirectorySize { /* Dan Czarnecki October 24, 2013 Class variables: private File directory A File object that holds the pathname of the directory to look in private long sizeInBytes A variable of type long that holds the size of a file/directory (in bytes) private long fileCount A variable of type long that holds the number of files in a directory Constructors: public DirectoryStatistics(File startingDirectory) throws FileNotFoundException Creates a DirectoryStatistics object, given a pathname (inherited from DirectorySize class), and has 3 instance variables that hold the directory to search in, the size of each file (in bytes), and the number of files within the directory Modification history: October 24, 2013 Original version of class */ private File directory; private long sizeInBytes; private long fileCount; public DirectoryStatistics(File startingDirectory) throws FileNotFoundException { super(startingDirectory); try { if(directory == null) { throw new IllegalArgumentException("null input"); } if(directory.isDirectory() == false) { throw new FileNotFoundException("the following input is not a directory!"); } } catch(IOException ioe) { System.out.println("You have not entered a directory. Please try again."); } } public File getDirectory() { return this.directory; } public long getSizeInBytes() { return this.sizeInBytes; } public long getFileCount() { return this.fileCount; } public long setFileCount(long size) { fileCount = size; return size; } public long setSizeInBytes(long size) { sizeInBytes = size; return size; } public void incrementFileCount() { fileCount = fileCount + 1; } public void addToSizeInBytes(long addend) { sizeInBytes = sizeInBytes + addend; } public String toString() { return "Directory" + this.directory + "Size (in bytes) " + this.sizeInBytes + "Number of files: " + this.fileCount; } public int hashCode() { return this.directory.hashCode(); } public boolean equals(DirectoryStatistics other) { return this.equals(other); } } import java.io.*; import java.util.*; public class DirectorySize extends DirectoryProcessor { /* Dan Czarnecki October 17, 2013 Class variables: private Vector<Long> directorySizeList Variable of type Vector<Long> that holds the total file size of files in that directory as well as files within folders of that directory private Vector<File> currentFile Variable of type Vector<File> that holds the parent directory Constructors: public DirectorySize(File startingDirectory) throws FileNotFoundException Creates a DirectorySize object, takes in a pathname (inherited from DirectoryProcessor class, and has a single vector of a DirectoryStatistics object to hold the files and folders within a directory Modification History October 17, 2013 Original version of class Implemented run() and processFile() methods */ private Vector<DirectoryStatistics> directory; /* private Vector<Long> directorySizeList; private Vector<File> currentFile; */ public DirectorySize(File startingDirectory) throws FileNotFoundException { super(startingDirectory); directory = new Vector<DirectoryStatistics>(); } public void processFile(File file) { DirectoryStatistics parent; int index; File parentFile; System.out.println(file.getName()); System.out.println(file.getParent()); parentFile = file.getParentFile(); parent = new DirectoryStatistics(parentFile); System.out.println(parent); parent.equals(parent); index = directory.indexOf(parent); if(index == 0) { directory.elementAt(index).addToSizeInBytes(file.length()); directory.elementAt(index).incrementFileCount(); } if(index < 0) { directory.addElement(parent); directory.lastElement().setSizeInBytes(file.length()); directory.lastElement().incrementFileCount(); } Could someone tell me why I'm getting this issue?

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  • iphone compass tilt compensation

    - by m01d
    hi, has anybody already programmed a iphone compass heading tilt compensation? i have got some approaches, but some help or a better solution would be cool! FIRST i define a vector Ev, calculated out of the cross product of Gv and Hv. Gv is a gravity vector i build out of the accelerometer values and Hv is an heading vector built out the magnetometer values. Ev stands perpendicular on Gv and Hv, so it is heading to horizonatl East. SECOND i define a vector Rv, calculated out of the cross product Bv and Gv. Bv is my looking vector and it is defined as [0,0,-1]. Rv is perpendicular to Gv and Bv and shows always to the right. THIRD the angle between these two vectors, Ev and Rv, should be my corrected heading. to calculate the angle i build the dot product and thereof the arcos. phi = arcos ( Ev * Rv / |Ev| * |Rv| ) Theoretically it should work, but maybe i have to normalize the vectors?! Has anybody got a solution for this? Thanks, m01d

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  • How do I reorder vector data using ARM Neon intrinsics?

    - by goldenmean
    This is specifically related to ARM Neon SIMD coding. I am using ARM Neon instrinsics for certain module in a video decoder. I have a vectorized data as follows: There are four 32 bit elements in a Neon register - say, Q0 - which is of size 128 bit. 3B 3A 1B 1A There are another four, 32 bit elements in other Neon register say Q1 which is of size 128 bit. 3D 3C 1D 1C I want the final data to be in order as shown below: 1D 1C 1B 1A 3D 3C 3D 3A What Neon instrinsics can achieve the desired data order?

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  • How do i a vector data using ARM Neon intrinsics?

    - by goldenmean
    Hello, This is specifically related to ARM Neon SIMD coding.I am using ARM Neon instrinsics for certain module in a Video Decoder. I have a vectorized data as follows:- There are four, 32 bit elements in a Neon register say Q0 which is of size 128 bit. 3B 3A 1B 1A There are another four, 32 bit elements in other Neon register say Q1 which is of size 128 bit. 3D 3C 1D 1C I want the final data to be in order as shown below:- 1D 1C 1B 1A 3D 3C 3D 3A Using what Neon instrinscis can achive the desired data order? thanks, -AD

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  • How should I manage data in an 2D vector based animation program?

    - by shadow
    I've been trying to design a program that makes 2D animations and then uses the ffmpeg library to create the video for possible use in tv and movies. The problem is when I think about how to manage the data in the application I can only think of two ways, I don't think either of them will work out very well. One is to use an SQlite database, but it seems like it will be difficult to save, especially if an artist puts 1000 things on screen. The other is to use something like linked lists, which would duplicate many features of the database and get complicated when dealing with things like points on a bezier curve and jumping to a frame and collecting all the objects that need to be drawn on that frame. Should I use one of these solutions, or is there something else that would be better? Currently planning to use C# for code.

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  • An algorithm Problem

    - by Vignesh
    For coverage, I've a set of run time variables of from my program execution. It happens that I get it from a series of executions(Automated testing). ie. its a vector<vector<var,value>> I've a limited set of variables with expected values and generate combination s, that is I have vector<vector<var,value>(smaller than the execution vector)>. Now I need to compare and tell which of the combination I generated were exactly executed in one of the tests. My algo is O(n^4). Is there any way to bring it down. Something like set intersection. I'm using java, and vectors because of thread safety.

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  • Why do we use Pythagoras in game physics?

    - by Starkers
    I've recently learned that we use Pythagoras a lot in our physics calculations and I'm afraid I don't really get the point. Here's an example from a book to make sure an object doesn't travel faster than a MAXIMUM_VELOCITY constant in the horizontal plane: MAXIMUM_VELOCITY = <any number>; SQUARED_MAXIMUM_VELOCITY = MAXIMUM_VELOCITY * MAXIMUM_VELOCITY; function animate(){ var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; x_velocity = x_velocity / scalar; z_velocity = x_velocity / scalar; } } Let's try this with some numbers: An object is attempting to move 5 units in x and 5 units in z. It should only be able to move 5 units horizontally in total! MAXIMUM_VELOCITY = 5; SQUARED_MAXIMUM_VELOCITY = 5 * 5; SQUARED_MAXIMUM_VELOCITY = 25; function animate(){ var x_velocity = 5; var z_velocity = 5; var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); var squared_horizontal_velocity = 5 * 5 + 5 * 5; var squared_horizontal_velocity = 25 + 25; var squared_horizontal_velocity = 50; // if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ if( 50 <= 25 ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; scalar = 50 / 25; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Now this works well, but we can do the same thing without Pythagoras: MAXIMUM_VELOCITY = 5; function animate(){ var x_velocity = 5; var z_velocity = 5; var horizontal_velocity = x_velocity + z_velocity; var horizontal_velocity = 5 + 5; var horizontal_velocity = 10; // if( horizontal_velocity >= MAXIMUM_VELOCITY ){ if( 10 >= 5 ){ scalar = horizontal_velocity / MAXIMUM_VELOCITY; scalar = 10 / 5; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Benefits of doing it without Pythagoras: Less lines Within those lines, it's easier to read what's going on ...and it takes less time to compute, as there are less multiplications Seems to me like computers and humans get a better deal without Pythagoras! However, I'm sure I'm wrong as I've seen Pythagoras' theorem in a number of reputable places, so I'd like someone to explain me the benefit of using Pythagoras to a maths newbie. Does this have anything to do with unit vectors? To me a unit vector is when we normalize a vector and turn it into a fraction. We do this by dividing the vector by a larger constant. I'm not sure what constant it is. The total size of the graph? Anyway, because it's a fraction, I take it, a unit vector is basically a graph that can fit inside a 3D grid with the x-axis running from -1 to 1, z-axis running from -1 to 1, and the y-axis running from -1 to 1. That's literally everything I know about unit vectors... not much :P And I fail to see their usefulness. Also, we're not really creating a unit vector in the above examples. Should I be determining the scalar like this: // a mathematical work-around of my own invention. There may be a cleverer way to do this! I've also made up my own terms such as 'divisive_scalar' so don't bother googling var divisive_scalar = (squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY); var divisive_scalar = ( 50 / 25 ); var divisive_scalar = 2; var multiplicative_scalar = (divisive_scalar / (2*divisive_scalar)); var multiplicative_scalar = (2 / (2*2)); var multiplicative_scalar = (2 / 4); var multiplicative_scalar = 0.5; x_velocity = x_velocity * multiplicative_scalar x_velocity = 5 * 0.5 x_velocity = 2.5 Again, I can't see why this is better, but it's more "unit-vector-y" because the multiplicative_scalar is a unit_vector? As you can see, I use words such as "unit-vector-y" so I'm really not a maths whiz! Also aware that unit vectors might have nothing to do with Pythagoras so ignore all of this if I'm barking up the wrong tree. I'm a very visual person (3D modeller and concept artist by trade!) and I find diagrams and graphs really, really helpful so as many as humanely possible please!

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  • Why do we use the Pythagorean theorem in game physics?

    - by Starkers
    I've recently learned that we use Pythagorean theorem a lot in our physics calculations and I'm afraid I don't really get the point. Here's an example from a book to make sure an object doesn't travel faster than a MAXIMUM_VELOCITY constant in the horizontal plane: MAXIMUM_VELOCITY = <any number>; SQUARED_MAXIMUM_VELOCITY = MAXIMUM_VELOCITY * MAXIMUM_VELOCITY; function animate(){ var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; x_velocity = x_velocity / scalar; z_velocity = x_velocity / scalar; } } Let's try this with some numbers: An object is attempting to move 5 units in x and 5 units in z. It should only be able to move 5 units horizontally in total! MAXIMUM_VELOCITY = 5; SQUARED_MAXIMUM_VELOCITY = 5 * 5; SQUARED_MAXIMUM_VELOCITY = 25; function animate(){ var x_velocity = 5; var z_velocity = 5; var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); var squared_horizontal_velocity = 5 * 5 + 5 * 5; var squared_horizontal_velocity = 25 + 25; var squared_horizontal_velocity = 50; // if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ if( 50 <= 25 ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; scalar = 50 / 25; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Now this works well, but we can do the same thing without Pythagoras: MAXIMUM_VELOCITY = 5; function animate(){ var x_velocity = 5; var z_velocity = 5; var horizontal_velocity = x_velocity + z_velocity; var horizontal_velocity = 5 + 5; var horizontal_velocity = 10; // if( horizontal_velocity >= MAXIMUM_VELOCITY ){ if( 10 >= 5 ){ scalar = horizontal_velocity / MAXIMUM_VELOCITY; scalar = 10 / 5; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Benefits of doing it without Pythagoras: Less lines Within those lines, it's easier to read what's going on ...and it takes less time to compute, as there are less multiplications Seems to me like computers and humans get a better deal without Pythagorean theorem! However, I'm sure I'm wrong as I've seen Pythagoras' theorem in a number of reputable places, so I'd like someone to explain me the benefit of using Pythagorean theorem to a maths newbie. Does this have anything to do with unit vectors? To me a unit vector is when we normalize a vector and turn it into a fraction. We do this by dividing the vector by a larger constant. I'm not sure what constant it is. The total size of the graph? Anyway, because it's a fraction, I take it, a unit vector is basically a graph that can fit inside a 3D grid with the x-axis running from -1 to 1, z-axis running from -1 to 1, and the y-axis running from -1 to 1. That's literally everything I know about unit vectors... not much :P And I fail to see their usefulness. Also, we're not really creating a unit vector in the above examples. Should I be determining the scalar like this: // a mathematical work-around of my own invention. There may be a cleverer way to do this! I've also made up my own terms such as 'divisive_scalar' so don't bother googling var divisive_scalar = (squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY); var divisive_scalar = ( 50 / 25 ); var divisive_scalar = 2; var multiplicative_scalar = (divisive_scalar / (2*divisive_scalar)); var multiplicative_scalar = (2 / (2*2)); var multiplicative_scalar = (2 / 4); var multiplicative_scalar = 0.5; x_velocity = x_velocity * multiplicative_scalar x_velocity = 5 * 0.5 x_velocity = 2.5 Again, I can't see why this is better, but it's more "unit-vector-y" because the multiplicative_scalar is a unit_vector? As you can see, I use words such as "unit-vector-y" so I'm really not a maths whiz! Also aware that unit vectors might have nothing to do with Pythagorean theorem so ignore all of this if I'm barking up the wrong tree. I'm a very visual person (3D modeller and concept artist by trade!) and I find diagrams and graphs really, really helpful so as many as humanely possible please!

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  • can't explain NullPointerException

    - by John Pope
    In the following code, i have a method to get a Vector of persons with the same zodiac sign. persoane is a Vector. I keep getting a NullPointerException at the if condition (persoane is definetly not null). I am unable to see why. Any help would be greatly appreciated public Vector<Persoana> cautaDupaZodie(String zodie) { Vector<Persoana> rezultat= new Vector<Persoana>(); for(int i=0; i<persoane.size(); i++) { if(persoane.get(i).getData().getZodie().equals(zodie)) //the exception occurs here { rezultat.add(persoane.get(i)); } } return rezultat; }

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  • Is there a module that implements an efficient array type in Erlang?

    - by dsmith
    I have been looking for an array type with the following characteristics in Erlang. append(vector(), term()) O(1) nth(Idx, vector()) O(1) set(Idx, vector(), term()) O(1) insert(Idx, vector(), term()) O(N) remove(Idx, vector()) O(N) I normally use a tuple for this purpose, but the performance characteristics are not what I would want for large N. My testing shows the following performance characteristics... erlang:append_element/2 O(N). erlang:setelement/3 O(N). I have started on a module based on the clojure.lang.PersistentVector implementation, but if it's already been done I won't reinvent the wheel.

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  • Inline function and calling cost in C

    - by Eonil
    I'm making a vector/matrix library. (GCC, ARM NEON, iPhone) typedef struct{ float v[4]; } Vector; typedef struct{ Vector v[4]; } Matrix; I passed struct data as pointer to avoid performance degrade from data copying when calling function. So I thought designed function like this: void makeTranslation(const Vector* factor, Matrix* restrict result); But, if function is inline, is there any reason to pass values as pointer for performance? Do those variables copied too? How about register and caches? inline Matrix makeTranslation(Vector factor) __attribute__ ((always_inline)); How do you think about calling costs of each cases?

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  • c struct map to ruby using SWIG

    - by pierr
    Hi, Is there any body can confirm the description here is true? My experience is that I can not use Example::Vector.new at all. C/C++ structs are wrapped as Ruby classes, with accessor methods (i.e. "getters" and "setters") for all of the struct members. For example, this struct declaration: struct Vector { double x, y; }; gets wrapped as a Vector class, with Ruby instance methods x, x=, y and y=. These methods can be used to access structure data from Ruby as follows: $ irb irb(main):001:0> require 'Example' true irb(main):002:0> f = Example::Vector.new #<Example::Vector:0x4020b268> irb(main):003:0> f.x = 10 nil irb(main):004:0> f.x 10.0

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  • How do I get characters common to two vectors in C++?

    - by Sam Phelps
    I am trying to compare two vector objects, and return a single vector containing all the chars which appear in both vectors. How would I go about this without writing some horribly complex manual method which compares every char in the first vector to every char in the second vector and using an if to add it to a third vector (which would be returned) if they match. Maybe my lack of real experience with vectors is making me imagine this will be harder than it really is, but I suspect there is some simplier way which I have been unable to find through searching.

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  • How do I compare vectors in C++?

    - by Sam Phelps
    I am trying to compare two vector objects, and return a single vector containing all the chars which appear in both vectors. How would I go about this without writing some horribly complex manual method which compares every char in the first vector to every char in the second vector and using an if to add it to a third vector (which would be returned) if they match. Maybe my lack of real experience with vectors is making me imagine this will be harder than it really is, but I suspect there is some simplier way which I have been unable to find through searching.

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  • Clojure: I have many sorted maps and want to reduce in order all there values a super maps of keys -> vector

    - by Alex Foreman
    I have seen this but can't work out how to apply it (no pun intended) to my situation. I have a sorted list of maps like this: (note there can be more than two keys in the map) ({name1 3, name2 7}, {name1 35, name2 7}, {name1 0, name2 3}) What I am after is this data structure afterwards: ({:name1 [3,35,0]}, {:name2 [7,7,3]}) Ive been struggling with this for a while and cant seem to get anywhere near. Caveats: The data must stay sorted and I have N keywords not just two.

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  • C++ iterators problem

    - by qwead
    I'm working with iterators on C++ and I'm having some trouble here. It says "Debug Assertion Failed" on expression (this-_Has_container()) on line interIterator++. Distance list is a vector< vector< DistanceNode . What I'm I doing wrong? vector< vector<DistanceNode> >::iterator externIterator = distanceList.begin(); while (externIterator != distanceList.end()) { vector<DistanceNode>::iterator interIterator = externIterator->begin(); while (interIterator != externIterator->end()){ if (interIterator->getReference() == tmp){ //remove element pointed by interIterator externIterator->erase(interIterator); } // if interIterator++; } // while externIterator++; } // while

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