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  • comparing two angles

    - by Elazar Leibovich
    Given four points in the plane, A,B,X,Y, I wish to determine which of the following two angles is smaller ?ABX or ?ABY. I'd rather not use cos or sqrt, in order to preserve accuracy. In the case where A=(-1,0),B=(0,0), I can compare the two angles ?ABX and ?ABY, by calculating the dot product of the vectors X,Y, and watch it's sign. What I can do in this case is: Determine whether or not ABX turns right or left If ABX turns left check whether or not Y and A are on the same side of the line on segment BX. If they are - ?ABX is a smaller than ABY. If ABX turns right, then Y and A on the same side of BX means that ?ABX is larger than ?ABY. But this seems too complicated to me. Any simpler approach?

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  • Do I need to check capacity before adding an element to a vector in c++ ?

    - by Cassie
    Hi dear all, I am a newbie to c++ STL vectors so sorry for silly questions in advence. :) In my program, I have a vector which needs to store unknown number of elements. Do I have to check if the vector has achieved its max_size before adding an new element to it ? Will a c++ compiler throw an exception automatically when a program tries to add elements to a full vector ? Thank you very much, Cassie

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  • Init modules in apache2

    - by user306963
    Hello, I used to write apache modules in apache 1.3, but these days I am willing to pass to apache2. The module that I am writing at the moment has is own binary data, not a database, for performance purposes. I need to load this data in shared memory, so every child can access it without making his own copy, and it would be practical to load/create the binary data at startup, as I was used to do with apache 1.3. Problem is that I don't find an init event in apache2, in 1.3 in the module struct, immediatly after STANDARD_MODULE_STUFF you find a place for a /** module initializer */, in which you can put a function that will be executed early. Body of the function I used to write is something like: if ( getppid == 1 ) { // Load global data here // this is the parent process void* data = loadGlobalData( someFilePath ); setGlobalData( config, data ); } else { // this is the init of a child process // do nothing } I am looking for a place in apache2 in where I can put a similar function. Can you help? Thanks Benvenuto

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  • Draw Lines Over a Circle

    - by VOX
    There's a line A-B and C at the center between A and B. It forms a circle as in the figure. If we assume A-B line as a diameter of the circle and then C is it's center. My problem is I have no idea how to draw another three lines (in blue) each 45 degree away from AC or AB. No, this is not a homework, it's part of my complex geometry in a rendering. http://www.freeimagehosting.net/image.php?befcd84d8c.png

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  • Intersection of line with cube and knowing the point of intersection.

    - by Raj
    Hello everyone, description 1.lines are originating from origin(0,0,0). 2.lines are at some random angle to the Normal of Top face of teh cube. 3.if the lines are intersecting cube , calculate the intersection point. 4.mainly i wan to know how much distance ,line traveled inside the cube. I dont know exactly which approach should i take , i will be pleased and thankful if someone could guied me to the right direction, to use OpenGL, DirectX or some other library, for C# . some example or sample will be appriciated.

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  • AES Cipher not picking up IV

    - by timothyjc
    I am trying to use an IV with AES so that the encrypted text is unpredictable. However, the encrypted hex string is always the same. I have actually tried a few methods of attempting to add some randomness by passing some additional parameters to the cipher init call: 1) Manual IV generation byte[] iv = generateIv(); IvParameterSpec ivspec = new IvParameterSpec(iv); 2) Asking cipher to generate IV AlgorithmParameters params = cipher.getParameters(); params.getParameterSpec(IvParameterSpec.class); 3) Using a PBEParameterSpec byte[] encryptionSalt = generateSalt(); PBEParameterSpec pbeParamSpec = new PBEParameterSpec(encryptionSalt, 1000); All of these seem to have no influence on the encrypted text.... help!!! My code: package com.citc.testencryption; import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import javax.crypto.Cipher; import javax.crypto.SecretKey; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.PBEKeySpec; import android.app.Activity; import android.os.Bundle; import android.util.Log; public class Main extends Activity { public static final int SALT_LENGTH = 20; public static final int PBE_ITERATION_COUNT = 1000; private static final String RANDOM_ALGORITHM = "SHA1PRNG"; private static final String PBE_ALGORITHM = "PBEWithSHA256And256BitAES-CBC-BC"; private static final String CIPHER_ALGORITHM = "PBEWithSHA256And256BitAES-CBC-BC"; private static final String TAG = Main.class.getSimpleName(); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); try { String password = "password"; String plainText = "plaintext message to be encrypted"; // byte[] salt = generateSalt(); byte[] salt = "dfghjklpoiuytgftgyhj".getBytes(); Log.i(TAG, "Salt: " + salt.length + " " + HexEncoder.toHex(salt)); PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray(), salt, PBE_ITERATION_COUNT); SecretKeyFactory keyFac = SecretKeyFactory.getInstance(PBE_ALGORITHM); SecretKey secretKey = keyFac.generateSecret(pbeKeySpec); byte[] key = secretKey.getEncoded(); Log.i(TAG, "Key: " + HexEncoder.toHex(key)); // PBEParameterSpec pbeParamSpec = new PBEParameterSpec(salt, ITERATION_COUNT); Cipher encryptionCipher = Cipher.getInstance(CIPHER_ALGORITHM); // byte[] encryptionSalt = generateSalt(); // Log.i(TAG, "Encrypted Salt: " + encryptionSalt.length + " " + HexEncoder.toHex(encryptionSalt)); // PBEParameterSpec pbeParamSpec = new PBEParameterSpec(encryptionSalt, 1000); // byte[] iv = params.getParameterSpec(IvParameterSpec.class).getIV(); // Log.i(TAG, encryptionCipher.getParameters() + " "); byte[] iv = generateIv(); IvParameterSpec ivspec = new IvParameterSpec(iv); encryptionCipher.init(Cipher.ENCRYPT_MODE, secretKey, ivspec); byte[] encryptedText = encryptionCipher.doFinal(plainText.getBytes()); Log.i(TAG, "Encrypted: " + HexEncoder.toHex(encryptedText)); // <== Why is this always the same :( Cipher decryptionCipher = Cipher.getInstance(CIPHER_ALGORITHM); decryptionCipher.init(Cipher.DECRYPT_MODE, secretKey, ivspec); byte[] decryptedText = decryptionCipher.doFinal(encryptedText); Log.i(TAG, "Decrypted: " + new String(decryptedText)); } catch (Exception e) { e.printStackTrace(); } } private byte[] generateSalt() throws NoSuchAlgorithmException { SecureRandom random = SecureRandom.getInstance(RANDOM_ALGORITHM); byte[] salt = new byte[SALT_LENGTH]; random.nextBytes(salt); return salt; } private byte[] generateIv() throws NoSuchAlgorithmException { SecureRandom random = SecureRandom.getInstance(RANDOM_ALGORITHM); byte[] iv = new byte[16]; random.nextBytes(iv); return iv; } }

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  • How do I replace colours in a movieclip?

    - by Oli
    I am trying to take a movieclip of a character and change the colour of their clothes. The character is comprised of vectors. So far I have semi-sucessfully used this method: stop the movieclip take the bitmap data from the current frame use threshold to replace the colour store the resulting bitmap data in an array add an onenterframe function - clear the current frame and add the bitmap data from the processed data in the array So - this works pretty well. Each frame is only processed once at the beginning and then the write to the movieclip is very quick. However! As the replacement is being performed on a bitmap there is an amount of aliasing that takes place to remove jaggies/pixelation. This produces colours that are not matched using threshold. So the main colour is replaced correctly but it is surrounded by a halo of mixed colours :( I am sure there should be a better way to do this. Any ideas or answers would be greatly apreciated - Thanks.

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  • solving origin of a vectors

    - by Mike
    I have two endpoints (xa,ya) and (xb,yb) of two vectors, respectively a and b, originating from a same point (xo, yo). Also, I know that |a|=|b|+s, where s is a constant. I tried to compute the origin (xo, yo) but seem to fail at some point. How to solve this?

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  • Java: how to initialize int without assigning a value?

    - by HH
    $ javac InitInt.java InitInt.java:9: '[' expected right = new int; ^ InitInt.java:9: ']' expected right = new int; ^ InitInt.java:13: ';' expected } ^ InitInt.java:14: ';' expected public int getRight(){return right;} ^ InitInt.java:15: reached end of file while parsing } ^ 5 errors $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; public static void main(String[] args) { // I don't want to assign any value. // just initialize it, how? right = new int; // later assiging a value } public int getRight(){return right;} }

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  • C# Initialize Subclass based on Parent object

    - by ctrlShiftBryan
    So basically I have this public class Ticket{ public TicketNumber {get; set;} ..a bunch more properties... } I want to add some properties using a subclass like this using subsumption instead of composition. public class TicketViewModel(Ticket ticket){ //set each property from value of Ticket passed in this.TicketNumber = ticket.TicketNumber; ...a bunch more lines of code.. //additional VM properties public SelectList TicketTypes {get; private set;} } How do I instantiate the properties without having to write all the lines like this this.TicketNumber = ticket.TicketNumber; Is there some kind of shortcut? Something like in the subclass constructor? this = ticket; Obviously this doesn't work but is their some way so I don't have to modify my subclass if addng/removing a property to the parent class? Or something?

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  • How to modify a given class to use const operators

    - by zsero
    I am trying to solve my question regarding using push_back in more than one level. From the comments/answers it is clear that I have to: Create a copy operator which takes a const argument Modify all my operators to const But because this header file is given to me there is an operator what I cannot make into const. It is a simple: float & operator [] (int i) { return _item[i]; } In the given program, this operator is used to get and set data. My problem is that because I need to have this operator in the header file, I cannot turn all the other operators to const, what means I cannot insert a copy operator. How can I make all my operators into const, while preserving the functionality of the already written program? Here is the full declaration of the class: class Vector3f { float _item[3]; public: float & operator [] (int i) { return _item[i]; } Vector3f(float x, float y, float z) { _item[0] = x ; _item[1] = y ; _item[2] = z; }; Vector3f() {}; Vector3f & operator = ( const Vector3f& obj) { _item[0] = obj[0]; _item[1] = obj[1]; _item[2] = obj[2]; return *this; }; Vector3f & operator += ( const Vector3f & obj) { _item[0] += obj[0]; _item[1] += obj[1]; _item[2] += obj[2]; return *this; }; bool operator ==( const Vector3f & obj) { bool x = (_item[0] == obj[0]) && (_item[1] == obj[1]) && (_item[2] == obj[2]); return x; } // my copy operator Vector3f(const Vector3f& obj) { _item[0] += obj[0]; _item[1] += obj[1]; _item[2] += obj[2]; return this; } };

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  • Please explain this python behavior

    - by StackUnderflow
    class SomeClass(object): def __init__(self, key_text_pairs = None): ..... for key, text in key_text_pairs: ...... ...... x = SomeClass([1, 2, 3]) The value of key_text_pairs inside the init is None even if I pass a list as in the above statement. Why is it so?? I want to write a generic init which can take all iterator objects... Thanks

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  • How to set global variables to use everywhere in my application?

    - by user502052
    I am using Ruby on Rails 3 and I would like to set some global variable to use those everywhere in my application. In particular, the domain name. If, for example, my website URL is http://subname.domain.com I would like to set or retrieve the subname.domain.com value in order to use that in my application like this request_uri = "http://#{sub_domain_name}" Where and how I have to state\initialize the sub_domain_name variable or other variables at all?

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  • NumPy: how to quickly normalize many vectors?

    - by EOL
    How can a list of vectors be elegantly normalized, in NumPy? Here is an example that does not work: from numpy import * vectors = array([arange(10), arange(10)]) # All x's, then all y's norms = apply_along_axis(linalg.norm, 0, vectors) # Now, what I was expecting would work: print vectors.T / norms # vectors.T has 10 elements, as does norms, but this does not work The last operation yields "shape mismatch: objects cannot be broadcast to a single shape". How can the normalization of the 2D vectors in vectors be elegantly done, with NumPy? Edit: Why does the above not work while adding a dimension to norms does work (as per my answer below)?

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  • Reinitialize the current month name, when i click button

    - by EswaraMoorthyNEC
    Hi,In my richCalendar.jsp page, first time i click the showCurrentMonth button and display the current month using rich:calendar. i select some other month i click SelectedMonth button. I show the selected month name. My problem is : I go to any other page. then i come visit the richCalendar.jsp and again click showCurrentMonth button, this time the rich:calendar show the already selected month instead of current month . Each time, i want to show current month when i click showCurrentMonth. richCalendar.jsp <body> <h:form id="calendarForm" binding="#{CalenderBean.initForm}"> <rich:panel> <a4j:outputPanel id="calendarOutputPanel"> <h:panelGrid> <a4j:commandButton value="showCurrentMonth" action="#{CalenderBean.showCurrentMonthAction}" reRender="monthlyPanelGridId,monthlyCalendarId,calendarOutputPanel"/> <h:panelGrid id="monthlyPanelGridId" rendered="#{CalenderBean.monthlyCalendarRendered}" > <rich:calendar boundaryDatesMode="scroll" id="monthlyCalendarId" showWeekDaysBar="false" oncurrentdateselected="event.rich.component.selectDate(event.rich.date)" showFooter="false" popup="false" value="#{CalenderBean.selectedMonth}"/> </h:panelGrid> <h:panelGrid id = "SearchButtonGrid"> <a4j:commandButton id="SelectedMonth" value="SelectedMonth" action="#{CalenderBean.selectedMonthButtonAction}" reRender="calendarOutputPanel"/> <h:outputText value="#{CalenderBean.selectedMonthName}" /> </h:panelGrid> </h:panelGrid> </a4j:outputPanel> <rich:panel></h:form></body> CalenderBean.java import java.util.Calendar; import java.util.Date; import javax.faces.component.html.HtmlForm; public class CalenderBean { private HtmlForm initForm; private boolean monthlyCalendarRendered; private Date selectedMonth; private String selectedMonthName; public CalenderBean() { } public String showCurrentMonthAction() { monthlyCalendarRendered = true; Calendar calendar = Calendar.getInstance(); int startingDate = calendar.getActualMinimum(Calendar.DAY_OF_MONTH); calendar.set(Calendar.DATE, startingDate); selectedMonth = calendar.getTime(); return ""; } public String selectedMonthButtonAction() { selectedMonthName = selectedMonth.toString(); return ""; } public HtmlForm getInitForm() { selectedMonth = null; monthlyCalendarRendered = false; return initForm; } public void setInitForm(HtmlForm initForm){ this.initForm = initForm; } public boolean isMonthlyCalendarRendered(){ return monthlyCalendarRendered; } public void setMonthlyCalendarRendered(boolean monthlyCalendarRendered){ this.monthlyCalendarRendered = monthlyCalendarRendered; } public Date getSelectedMonth(){ return selectedMonth; } public void setSelectedMonth(Date selectedMonth){ this.selectedMonth = selectedMonth; } public String getSelectedMonthName(){ return selectedMonthName; } public void setSelectedMonthName(String selectedMonthName){ this.selectedMonthName = selectedMonthName; } } First time i visit this page perfectly show the current month. Then i go to any othe page and then come to see this page, click showCurrentMonth button not show the current month. Help me. Thanks in advance.

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  • How to transform a vector<int> into a string?

    - by Legend
    I am trying to pass a value from C++ to TCL. As I cannot pass pointers without the use of some complicated modules, I was thinking of converting a vector to a char array and then passing this as a null terminated string (which is relatively easy). I have a vector as follows: 12, 32, 42, 84 which I want to convert into something like: "12 32 42 48" The approach I am thinking of is to use an iterator to iterate through the vector and then convert each integer into its string representation and then add it into a char array (which is dynamically created initially by passing the size of the vector). Is this the right way or is there a function that already does this?

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  • Setting the initial value of a property when using DataContractSerializer

    - by Eric
    If I am serializing and later deserializing a class using DataContractSerializer how can I control the initial values of properties that were not serialized? Consider the Person class below. Its data contract is set to serialize the FirstName and LastName properties but not the IsNew property. I want IsNew to initialize to TRUE whether a new Person is being instantiate as a new instance or being deserialized from a file. This is easy to do through the constructor, but as I understand it DataContractSerializer does not call the constructor as they could require parameters. [DataContract(Name="Person")] public class Person { [DataMember(Name="FirstName")] public string FirstName { get; set; } [DataMember(Name = "LastName")] public string LastName { get; set; } public bool IsNew { get; set; } public Person(string first, string last) { this.FirstName = first; this.LastName = last; this.IsNew = true; } }

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  • FastVectorHighlighter.Net returning null on GetBestFragment

    - by Midhat
    Hi I have a large index, on which Highlighter.Net works fine, but FastVectorHighlighter returns null as a Best Fragment on Some documents. the searcher works fine. It is just the highlighter. The field has been indexed in the same manner for all documents, so I fail to understand Why it highlights some documents but not all. Using Lucene.Net 2.9.2, built from trunk rev942061

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  • How to initialize a web app?

    - by Gatis
    My Web App will be deployed as a WAR package in a Jetty instance. It needs to perform a lot of caching before serving requests. How do I call the caching method before anything else? is the a static void main() in the web app standard?

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  • main vs initialize in Ruby

    - by Dave
    Okay, so I've looked through a couple of my ruby books and done some googling to no avail. What is the difference between main and initialize in Ruby? I've seen code that uses class Blahblah def main some logic here end #more methods... end and then calls it using Blahblah.new. Isn't new reserved only for initialize? if not, then what's the difference between the two?

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  • initialising a 2-dim Array in Scala

    - by Stefan W.
    (Scala 2.7.7:) I don't get used to 2d-Arrays. Arrays are mutable, but how do I specify a 2d-Array which is - let's say of size 3x4. The dimension (2D) is fixed, but the size per dimension shall be initializable. I tried this: class Field (val rows: Int, val cols: Int, sc: java.util.Scanner) { var field = new Array [Char](rows)(cols) for (r <- (1 to rows)) { val line = sc.nextLine () val spl = line.split (" ") field (r) = spl.map (_.charAt (0)) } def put (val rows: Int, val cols: Int, c: Char) = todo () } I get this error: :11: error: value update is not a member of Char field (r) = spl.map (_.charAt (0)) If it would be Java, it would be much more code, but I would know how to do it, so I show what I mean: public class Field { private char[][] field; public Field (int rows, int cols, java.util.Scanner sc) { field = new char [rows][cols]; for (int r = 0; r < rows; ++r) { String line = sc.nextLine (); String[] spl = line.split (" "); for (int c = 0; c < cols; ++c) field [r][c] = spl[c].charAt (0); } } public static void main (String args[]) { new Field (3, 4, new java.util.Scanner ("fraese.fld")); } } and fraese.fld would look, for example, like that: M M M M . M I get some steps wide with val field = new Array Array [Char] but how would I then implement 'put'? Or is there a better way to implement the 2D-Array. Yes, I could use a one-dim-Array, and work with put (y, x, c) = field (y * width + x) = c but I would prefer a notation which looks more 2d-ish.

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  • Managing Instances in Python

    - by BeensTheGreat
    Hello, I am new to Python and this is my first time asking a stackOverflow question, but a long time reader. I am working on a simple card based game but am having trouble managing instances of my Hand class. If you look below you can see that the hand class is a simple container for cards(which are just int values) and each Player class contains a hand class. However, whenever I create multiple instances of my Player class they all seem to manipulate a single instance of the Hand class. From my experience in C and Java it seems that I am somehow making my Hand class static. If anyone could help with this problem I would appreciate it greatly. Thank you, Thad To clarify: An example of this situation would be p = player.Player() p1 = player.Player() p.recieveCard(15) p1.recieveCard(21) p.viewHand() which would result in: [15,21] even though only one card was added to p Hand class: class Hand: index = 0 cards = [] #Collections of cards #Constructor def __init__(self): self.index self.cards def addCard(self, card): """Adds a card to current hand""" self.cards.append(card) return card def discardCard(self, card): """Discards a card from current hand""" self.cards.remove(card) return card def viewCards(self): """Returns a collection of cards""" return self.cards def fold(self): """Folds the current hand""" temp = self.cards self.cards = [] return temp Player Class import hand class Player: name = "" position = 0 chips = 0 dealer = 0 pHand = [] def __init__ (self, nm, pos, buyIn, deal): self.name = nm self.position = pos self.chips = buyIn self.dealer = deal self.pHand = hand.Hand() return def recieveCard(self, card): """Recieve card from the dealer""" self.pHand.addCard(card) return card def discardCard(self, card): """Throw away a card""" self.pHand.discardCard(card) return card def viewHand(self): """View the players hand""" return self.pHand.viewCards() def getChips(self): """Get the number of chips the player currently holds""" return self.chips def setChips(self, chip): """Sets the number of chips the player holds""" self.chips = chip return def makeDealer(self): """Makes this player the dealer""" self.dealer = 1 return def notDealer(self): """Makes this player not the dealer""" self.dealer = 0 return def isDealer(self): """Returns flag wether this player is the dealer""" return self.dealer def getPosition(self): """Returns position of the player""" return self.position def getName(self): """Returns name of the player""" return self.name

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  • Java: 2-assignments-2-initializations inside for-loop not allowed?

    - by HH
    $ javac MatchTest.java MatchTest.java:7: ')' expected for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ MatchTest.java:7: ';' expected for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ MatchTest.java:7: ';' expected for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ MatchTest.java:7: not a statement for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ MatchTest.java:7: illegal start of expression for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ 5 errors $ cat MatchTest.java import java.util.*; import java.io.*; public class MatchTest { public static void main(String[] args){ String text = "hello0123456789hello0123456789hello1234567890hello3423243423232"; for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) System.out.println(i); } }

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