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  • Finding the digit root of a number

    - by Jessica M.
    Study question is to find the digit root of a already provided number. The teacher provides us with the number 2638. In order to find the digit root you have to add each digit separately 2 + 6 + 3 + 8 = 19. Then you take the result 19 and add those two digits together 1 + 9 = 10. Do the same thing again 1 + 0 = 1. The digit root is 1. My first step was to use the variable total to add up the number 2638 to find the total of 19. Then I tried to use the second while loop to separate the two digits by using the % I have to try and solve the problem by using basic integer arithmetic (+, -, *, /). 1.Is it necessary and or possible to solve the problem using nested while loops? 2.Is my math correct? 3. As I wrote it here it does not run in Eclipse. Am I using the while loops correctly? import acm.program.*; public class Ch4Q7 extends ConsoleProgram { public void run(){ println("This program attempts to find the digit root of your number: "); int n = readInt("Please enter your number: "); int total = 0; int root = total; while (n > 0 ){ total = total + (n %10); n = (n / 10); } while ( total > 0 ){ root = total; total = ((total % 10) + total / 10); } println("your root should be " + root); } }

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  • C++ OOP - Can you 'overload a cast' <- hard to explain in 1 sentence

    - by Brandon Miller
    Well, the WinAPI has a POINT struct, but I am trying to make an alternative class to this so you can set the values of x and y from a constructor. /** * X-Y coordinates */ class Point { public: int X, Y; Point(void) : X(0), Y(0) {} Point(int x, int y) : X(x), Y(y) {} Point(const POINT& pt) : X(pt.x), Y(pt.y) {} Point& operator= (const POINT& other) { X = other.x; Y = other.y; } }; // I have an assignment operator and copy constructor. Point myPtA(3,7); Point myPtB(8,5); POINT pt; pt.x = 9; pt.y = 2; // I can assign a 'POINT' to a 'Point' myPtA = pt; // But I also want to be able to assign a 'Point' to a 'POINT' pt = myPtB; Is it possible to overload operator= in a way so that I can assign a Point to a POINT? Or maybe some other method to achieve this? Thanks in advance.

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  • Why null reference exception in SetMolePublicInstance?

    - by OldGrantonian
    I get a "null reference" exception in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, null); The program builds and compiles correctly. There are no complaints about any of the parameters to the method. Here's the specification of SetMolePublicInstance, from the object browser: SetMolePublicInstance(System.Delegate _stub, System.Type receiverType, object _receiver, string name, params System.Type[] parameterTypes) Here are the parameter values for "Locals": + stub {Method = {System.String <StaticMethodUnitTestWithDeq>b__0()}} System.Func<string> + receiverType {Name = "OrigValue" FullName = "OrigValueP.OrigValue"} System.Type {System.RuntimeType} objReceiver {OrigValueP.OrigValue} object {OrigValueP.OrigValue} name "TestString" string parameterTypes null object[] I know that TestString() takes no parameters and returns string, so as a starter to try to get things working, I specified "null" for the final parameter to SetMolePublicInstance. As already mentioned, this compiles OK. Here's the stack trace: Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.ExtendedReflection.Collections.Indexable.ConvertAllToArray[TInput,TOutput](TInput[] array, Converter`2 converter) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMole(Delegate _stub, Type receiverType, Object _receiver, String name, MoleBindingFlags flags, Type[] parameterTypes) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(Delegate _stub, Type receiverType, Object _receiver, String name, Type[] parameterTypes) at DeqP.Deq.Replace[T](Func`1 stub, Type receiverType, Object objReceiver, String name) in C:\0VisProjects\DecP_04\DecP\DeqC.cs:line 38 at DeqPTest.DecCTest.StaticMethodUnitTestWithDeq() in C:\0VisProjects\DecP_04\DecPTest\DeqCTest.cs:line 28 at Starter.Start.Main(String[] args) in C:\0VisProjects\DecP_04\Starter\Starter.cs:line 14 Press any key to continue . . . To avoid the null parameter, I changed the final "null" to "parameterTypes" as in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, parameterTypes); I then tried each of the following (before the line): int[] parameterTypes = null; // if this is null, I don't think the type will matter int[] parameterTypes = new int[0]; object[] parameterTypes = new object[0]; // this would allow for various parameter types All three attempts produce a red squiggly line under the entire line for SetMolePublicInstance Mouseover showed the following message: The best overloaded method match for 'Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(System.Delegate, System.Type, object, string, params System.Type[])' has some invalid arguments. I'm assuming that the first four arguments are OK, and that the problem is with the params array.

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  • Problem with SqlLite database in Qt SDK 1.0.2

    - by Risino
    Hi I have a problem with SqlLite database. Here is my code: void incomeDialog::on_add_pushButton_clicked() { int a = ui->income_lineEdit->text().toInt(); int b = ui->other_lineEdit->text().toInt(); int c = (a+b); db = QSqlDatabase::addDatabase("QSQLITE"); db.setDatabaseName("money.db"); QSqlQuery query(db); query.exec("create table Income" "(Month TEXT, Payment NUMBER, Other NUMBER, Together NUMBER)"); query.prepare("INSERT INTO Income values (?,?,?,?)"); query.addBindValue(ui->comboBox->currentText()); query.addBindValue(ui->income_lineEdit->text().toInt()); query.addBindValue(ui->other_lineEdit->text().toInt()); query.addBindValue(c); query.exec(); } I use qt sdk 1.0.2. After building shows errors: Undefined reference to 'QSqlDatabase::addDatabase(QString const&, QString const&)... all errors is similar (Undefined reference to 'QSqlDatabase:: Do you have any idea how to repair it?

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  • C++ STL: How to iterate vector while requiring access to element and its index?

    - by Ashwin
    I frequently find myself requiring to iterate over STL vectors. While I am doing this I require access to both the vector element and its index. I used to do this as: typedef std::vector<Foo> FooVec; typedef FooVec::iterator FooVecIter; FooVec fooVec; int index = 0; for (FooVecIter i = fooVec.begin(); i != fooVec.end(); ++i, ++index) { Foo& foo = *i; if (foo.somethingIsTrue()) // True for most elements std::cout << index << ": " << foo << std::endl; } After discovering BOOST_FOREACH, I shortened this to: typedef std::vector<Foo> FooVec; FooVec fooVec; int index = -1; BOOST_FOREACH( Foo& foo, fooVec ) { ++index; if (foo.somethingIsTrue()) // True for most elements std::cout << index << ": " << foo << std::endl; } Is there a better or more elegant way to iterate over STL vectors when both reference to the vector element and its index is required? I am aware of the alternative: for (int i = 0; i < fooVec.size(); ++i) But I keep reading about how it is not a good practice to iterate over STL containers like this.

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  • I need to make a multithreading program (python)

    - by Andreawu98
    import multiprocessing import time from itertools import product out_file = open("test.txt", 'w') P = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p','q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',] N = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] M = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'] c = int(input("Insert the number of digits you want: ")) n = int(input("If you need number press 1: ")) m = int(input("If you need upper letters press 1: ")) i = [] if n == 1: P = P + N if m == 1: P = P + M then = time.time() def worker(): for i in product(P, repeat=c): #check every possibilities k = '' for z in range(0, c): # k = k + str(i[z]) # print each possibility in a txt without parentesis or comma out_file.write( k + '\n') # out_file.close() now = time.time() diff = str(now - then) # To see how long does it take print(diff) worker() time.sleep(10) # just to check console The code check every single possibility and print it out in a test.txt file. It works but I really can't understand how can I speed it up. I saw it use 1 core out of my quad core CPU so I thought Multi-threading might work even though I don't know how. Please help me. Sorry for my English, I am from Italy.

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  • How to use multiple identity numbers in one table?

    - by vincer
    I have an web application that creates printable forms, these forms have a unique number on them, the problem is I have 2 forms that separate numbers need to be created for them. ie) Form1- Numbered 2000000-2999999 Form2- Numbered 3000000-3999999 dbo.test2 - is my form information table Tsel - is my autoinc table for the 3000000 series numbers Tadv - is my autoinc table for the 2000000 series numbers What I have done is create 2 tables with just autoinc row (one for 2000000 series numbers and one for 3000000 series numbers), I then created a trigger to add a record to the coresponding table, read back the autoinc number and add it to my table that stores the form information including the just created autoinc number for the right series of forms. Although it does work, I'm concerned that the numbers will get messed up under load. I'm not sure the @@IDENTITY will always return the right value when many people are using the system. (I cannot have duplicates and I need to use the numbering form show above. See code below. ** TRIGGER ** CREATE TRIGGER MAKEANID2 ON dbo.test2 AFTER INSERT AS SET NOCOUNT ON declare @someid int declare @someid2 int declare @startfrom int declare @test1 varchar(10) select @someid=@@IDENTITY select @test1 = (Select name1 from test2 where sysid = @someid ) if @test1 = 'select' begin insert into Tsel Default values select @someid2 = @@IDENTITY end if @test1 = 'adv' begin insert into Tadv Default values select @someid2 = @@IDENTITY end update test2 set name2=(@someid2) where sysid = @someid SET NOCOUNT OFF

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  • Asp.Net MVC3 - How create Dynamic DropDownList

    - by Bibo
    I found many articles on this but still I don´t know how exactly to do this. I am trying to create my own blog engine, I have View for create article (I am using EF and Code first) and now I must fill number of category in which article should be add but I want to change it to dropdownlist with names of categories. My model looks this: public class Article { public int ArticleID { get; set; } [Required] public string Title { get; set; } [Required] public int CategoryID { get; set; } public DateTime Date { get; set; } [Required()] [DataType(DataType.MultilineText)] [AllowHtml] public string Text { get; set; } public virtual Category Category { get; set; } public IEnumerable<SelectListItem> Categories { get; set; } public virtual ICollection<Comment> Comments { get; set; } } public class Category { public int CategoryID { get; set; } [Required] public string Name { get; set; } public virtual ICollection<Article> Articles { get; set; } } I know I must use Enum (or I think) but I am not exactly sure how. I don´t know which tutorial from that I found is best for me.

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  • What is the fastest (possibly unsafe) way to read a byte[]?

    - by Aidiakapi
    I'm working on a server project in C#, and after a TCP message is received, it is parsed, and stored in a byte[] of exact size. (Not a buffer of fixed length, but a byte[] of an absolute length in which all data is stored.) Now for reading this byte[] I'll be creating some wrapper functions (also for compatibility), these are the signatures of all functions I need: public byte ReadByte(); public sbyte ReadSByte(); public short ReadShort(); public ushort ReadUShort(); public int ReadInt(); public uint ReadUInt(); public float ReadFloat(); public double ReadDouble(); public string ReadChars(int length); public string ReadString(); The string is a \0 terminated string, and is probably encoded in ASCII or UTF-8, but I cannot tell that for sure, since I'm not writing the client. The data exists of: byte[] _data; int _offset; Now I can write all those functions manually, like this: public byte ReadByte() { return _data[_offset++]; } public sbyte ReadSByte() { byte r = _data[_offset++]; if (r >= 128) return (sbyte)(r - 256); else return (sbyte)r; } public short ReadShort() { byte b1 = _data[_offset++]; byte b2 = _data[_offset++]; if (b1 >= 128) return (short)(b1 * 256 + b2 - 65536); else return (short)(b1 * 256 + b2); } public short ReadUShort() { byte b1 = _data[_offset++]; return (short)(b1 * 256 + _data[_offset++]); } But I wonder if there's a faster way, not excluding the use of unsafe code, since this seems a little bit too much work for simple processing.

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  • Absence of property syntax in Java

    - by Vojislav Stojkovic
    C# has syntax for declaring and using properties. For example, one can declare a simple property, like this: public int Size { get; set; } One can also put a bit of logic into the property, like this: public string SizeHex { get { return String.Format("{0:X}", Size); } set { Size = int.Parse(value, NumberStyles.HexNumber); } } Regardless of whether it has logic or not, a property is used in the same way as a field: int fileSize = myFile.Size; I'm no stranger to either Java or C# -- I've used both quite a lot and I've always missed having property syntax in Java. I've read in this question that "it's highly unlikely that property support will be added in Java 7 or perhaps ever", but frankly I find it too much work to dig around in discussions, forums, blogs, comments and JSRs to find out why. So my question is: can anyone sum up why Java isn't likely to get property syntax? Is it because it's not deemed important enough when compared to other possible improvements? Are there technical (e.g. JVM-related) limitations? Is it a matter of politics? (e.g. "I've been coding in Java for 50 years now and I say we don't need no steenkin' properties!") Is it a case of bikeshedding?

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  • Mysql - Help me alter this query to apply AND logic instead of OR in searching?

    - by sandeepan-nath
    First execute these tables and data dumps :- CREATE TABLE IF NOT EXISTS `Tags` ( `id_tag` int(10) unsigned NOT NULL auto_increment, `tag` varchar(255) default NULL, PRIMARY KEY (`id_tag`), UNIQUE KEY `tag` (`tag`), KEY `id_tag` (`id_tag`), KEY `tag_2` (`tag`), KEY `tag_3` (`tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=18 ; INSERT INTO `Tags` (`id_tag`, `tag`) VALUES (1, 'key1'), (2, 'key2'); CREATE TABLE IF NOT EXISTS `Tutors_Tag_Relations` ( `id_tag` int(10) unsigned NOT NULL default '0', `id_tutor` int(10) default NULL, KEY `Tutors_Tag_Relations` (`id_tag`), KEY `id_tutor` (`id_tutor`), KEY `id_tag` (`id_tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO `Tutors_Tag_Relations` (`id_tag`, `id_tutor`) VALUES (1, 1), (2, 1); The following query finds all the tutors from Tutors_Tag_Relations table which have reference to at least one of the terms "key1" or "key2". SELECT td . * FROM Tutors_Tag_Relations AS td INNER JOIN Tags AS t ON t.id_tag = td.id_tag WHERE t.tag LIKE "%key1%" OR t.tag LIKE "%key2%" Group by td.id_tutor LIMIT 10 Please help me modify this query so that it returns all the tutors from Tutors_Tag_Relations table which have reference to both the terms "key1" and "key2" (AND logic instead of OR logic). Please suggest an optimized query considering huge number of data records (the query should NOT individually fetch two sets of tutors matching each keyword and then find the intersection).

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  • C++ string.substr() function problem

    - by VaioIsBorn
    I want to make a program that will read some number in string format and output it like this: if the number is 12345 it should then output 12 23 34 45 . I tried using the substr() function from the c++ string library, but it gives me strange results - it outputs 1 23 345 45 instead of the expected result. Why ? #include <iostream> #include <string> #include <cstdlib> using namespace std; int main(void) { string a;cin >> a; string b;int c; for(int i=0;i<a.size()-1;++i) { b = a.substr(i,i+1); c = atoi(b.c_str()); cout << c << " "; } cout << endl; return 0; }

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  • How can I modify the value of a string defined in a struct?

    - by Eric
    Hi, I have the following code in c++: #define TAM 4000 #define NUMPAGS 512 struct pagina { bitset<12> direccion; char operacion; char permiso; string *dato; int numero; }; void crearPagina(pagina* pag[], int pos, int dir) { pagina * paginas = (pagina*)malloc(sizeof(char) * TAM); paginas -> direccion = bitset<12> (dir); paginas -> operacion = 'n'; paginas -> permiso = 'n'; string **tempDato = &paginas -> dato; char *temp = " "; **tempDato = temp; paginas -> numero = 0; pag[pos] = paginas; } I want to modify the value of the variable called "string *dato" in the struct pagina but, everytime I want to assing a new value, the compiler throws a segmentation fault. In this case I'm using a pointer to string, but I have also tried with a string. In a few words I want to do the following: pagina - dato = "test"; Any idea? Thanks in advance!!!

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  • C# Freq. Table with Random Values

    - by Sef
    Hello, I am trying to write a frequency program that will represent a bar diagram (in console code). The problem is i have no idea how exactly to caculate this frequency or how do i exactly then give the bars different heights according to there frequency (trough calculation). The frequency height is capped at 21. (meaning the bars go from 1 to 21, so the max bar height would be for example 21 stars(* as display sign for the bar itself). A calculation i have so far (although not sure if correct) for frequency: This array takes the random values generated: for (int j = 0; j < T.Length; j++) { T[j] = (MaxHeight* T[j]) / Ber.GreatestElement(T); Console.Write("{0,7}", T[j]); } This results in values between 0 and 21 -- Based on the values my bars should give a certain height compared to all the other frequency values. (for example 8000 could have 21 in height where 39 could have 1). To represent this diagram i used 2 for loops to display height and width (keep in mind i only wish to use Using System; to keep it to the "basics"). for (int height= 1; height<= 21; height++) { for (int width= 0; width<= 10; width++) { if(...??) { Console.Write("{0,7}", bar); // string bar= ("*"); } else { Console.Write("{0,7}", empty); } } Console.WriteLine(); } So so far i have a entire field filled with * and the random values generated along with their frequency value (although i have no idea if the freq value is properly calculated). I assume i need a if (.....) in the second for but i cannot seem to get further then this. Thanks in advance!

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  • Strange compiler complaint when using similar code

    - by Jason
    For a project, I have to ask the user for a file name, and I'm reading it in character by character using getchar. From the main, I call the function char *coursename= introPrint(); //start off to print the usage directions and get the first bit of input. That function is defined as char *introPrint(){ int size= 20; int c; int length=0; char buffer[size]; //instructions printout, cut for brevity //get coursename from user and return it while ( (c=getchar()) != EOF && (c != '\n') ){ buffer[length++]= c; if (length==size-1) break; } buffer[length]=0; return buffer; } This is basically identical code I wrote to ask the user for input, replace the character echo with asterisks, then print out the results. Here, though, I'm getting a function returns address of local variable warning for the return statement. So why am I getting no warnings from the other program, but trigger one for this code?

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  • Attempted GCF app for Android

    - by Aaron
    I am new to Android and am trying to create a very basic app that calculates and displays the GCF of two numbers entered by the user. Here is a copy of my GCF.java: package com.example.GCF; import java.util.Arrays; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; public class GCF extends Activity { private TextView mAnswer; private EditText mA, mB; private Button ok; private String A, B; private int iA, iB; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mA = (EditText) findViewById(R.id.entry); mB = (EditText) findViewById(R.id.entry1); ok = (Button) findViewById(R.id.ok); mAnswer = (TextView) findViewById(R.id.answer1); ok.setOnClickListener(new OnClickListener() { public void onClick(View v) { A = mA.getText().toString(); B = mB.getText().toString(); } }); // the String to int conversion happens here iA = Integer.parseInt(A.trim()); iB = Integer.parseInt(B.trim()); while (iA != iB) { int[] nums={ iA, iB, Math.abs(iA-iB) }; Arrays.sort(nums); iA=nums[0]; iB=nums[1]; } updateDisplay(); } private void updateDisplay() { mAnswer.setText( new StringBuilder().append(iA)); } } Any Suggestions? Thank you!

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  • Calling base class constructor

    - by The Void
    In the program below, is the line Derived(double y): Base(), y_(y) correct/allowed? That is, does it follow ANSI rules? #include <iostream> class Base { public: Base(): x_(0) { std::cout << "Base default constructor called" << std::endl; } Base(int x): x_(x) { std::cout << "Base constructor called with x = " << x << std::endl; } void display() const { std::cout << x_ << std::endl; } protected: int x_; }; class Derived: public Base { public: Derived(): Base(1), y_(1.2) { std::cout << "Derived default constructor called" << std::endl; } Derived(double y): Base(), y_(y) { std::cout << "Derived constructor called with y = " << y << std::endl; } void display() const { std::cout << Base::x_ << ", " << y_ << std::endl; } private: double y_; }; int main() { Base b1; b1.display(); Derived d1; d1.display(); std::cout << std::endl; Base b2(-9); b2.display(); Derived d2(-8.7); d2.display(); return 0; }

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  • Reverse String Error?

    - by R41nB0w M47r1z
    I am creating this revese string App but i get a error if i include a space in the string ! #include <iostream> #include <string> using namespace std; int main() { int inputa; cout<<"%%%%%%%%%%%%%%%%%%String Reversing App%%%%%%%%%%%%%%%%%%%%%%%%"<<endl<<endl; cout<<"\nEnter 1 to continue and 0 to exit"<<endl<<endl; cin>>inputa; if(inputa!=0) { do { string a,c=""; cout<<"\nEnter the string you want to Reverse : "; cin>>a; for(int x=a.length()-1; x>=0; x--) { c=c+a.substr(x,1); } cout<<"\nThe Reverse String is : "<<c<<endl; cout<<"\nEnter 1 to continue and 0 to exit"<<endl<<endl; cin>>inputa; } while(inputa!=0); } //not my home work } If I type the following string like "abc def" there i get an error . But otherwise it works perfectly ! Is there some mistake with the codes ! I am new to CPP so it would be helpful if you could help me !

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  • C++: recursively computer all permutaions of digits 0 - 9

    - by Nate
    I have a homework assignment where part of the requirement is to recursively compute all the permutations of integers 0 - 9. The professor actually gave us the algorithm for this part of the question. I've finished the rest of the assignment, but I can't get the permute function working...I'm implementing it exactly like it was shown on the assignment information. However, when I run it each permutation is repeated multiple times (and I'm not sure if I'm even getting all the correct permutations.) I think he must've made a mistake on the assignment instructions. I've been working on this for a couple of hours and can't seem to figure out where I'm going wrong. Can anybody help point me in the right direction? Here's the current code: void permute(int v[], int curr) { for (int i = curr; i < MAX; i++) { swap(v[i], v[curr]); permute(v, curr + 1); swap(v[curr], v[i]); } } EDIT: Actually, right after posting this I realized it has to do with the swap, right? Because right now i and curr are the same, so I'm swapping identical numbers. Hm, should it be swap(v[i], v[curr+1])?

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  • Simulation tree command in C

    - by Ecle
    I have to create the simulation of tree command in C, this is my current code: #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <dirent.h> #include <string.h> main(int argc, char *argv[]){ int i; if(argc < 2){ printf("\nError. Use: %s directory\n", argv[0]); system("exit"); } for(i=1;i<argc;i++) //if(argv[i][0] != '-') tree(argv[i]); } tree(char *ruta){ DIR *dirp; struct dirent *dp; static nivel = 0; struct stat buf; char fichero[256]; int i; if((dirp = opendir(path)) == NULL){ perror(path); return; } while((dp = readdir(dirp)) != NULL){ printf(fichero, "%s/%s", path, dp->d_name); if((buf.st_mode & S_IFMT) == S_IFDIR){ for(i=0;i<nivel;i++) printf("\t"); printf("%s\n", dp->d_name); ++nivel; tree(fichero); --nivel; } } } Apparently, it works! (due to it compiles correctly) But I don't why. I can't pass the correct arguments to execute this. Thank you so much, people.

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  • "for" loop from program 7.6 from Kochan's "Programming in Objective-C"

    - by Mr_Vlasov
    "The sigma notation is shorthand for a summation. Its use here means to add the values of 1/2^i, where i varies from 1 to n. That is, add 1/2 + 1/4 + 1/8 .... If you make the value of n large enough, the sum of this series should approach 1. Let’s experiment with different values for n to see how close we get." #import "Fraction.h" int main (int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; Fraction *aFraction = [[Fraction alloc] init]; Fraction *sum = [[Fraction alloc] init], *sum2; int i, n, pow2; [sum setTo: 0 over: 1]; // set 1st fraction to 0 NSLog (@"Enter your value for n:"); scanf ("%i", &n); pow2 = 2; for (i = 1; i <= n; ++i) { [aFraction setTo: 1 over: pow2]; sum2 = [sum add: aFraction]; [sum release]; // release previous sum sum = sum2; pow2 *= 2; } NSLog (@"After %i iterations, the sum is %g", n, [sum convertToNum]); [aFraction release]; [sum release]; [pool drain]; return 0; } Question: Why do we have to create additional variable sum2 that we are using in the "for" loop? Why do we need "release previous sum" here and then again give it a value that we just released? : sum2 = [sum add: aFraction]; [sum release]; // release previous sum sum = sum2; Is it just for the sake of avoiding memory leakage? (method "add" initializes a variable that is stored in sum2)

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  • update attribute a element in arraylist on java ?

    - by tiendv
    I have a class Class TextChunks extends Token { ArrayList<Token> arrt = new ArrayList<Token>(); } extent fron class : class Token { String s; int frequency = 1 ;// Tern frequency in TextChunk } Now in token i have arraylist token , i want to update attribute frequency of token in Texchunks when have more than one tokens same . For clearly a give a example : Texchunks :" in particular in domain and range in some " So have 8 token : in,particular,in,domain,and,range,in,some i want update attribute frequency for token : in this example when i get attribute frequency of token "in" must return 3 it mean when i call : get frequency of Texchunks when dislay : in 3 particular 1 in 3 domain 1 and 1 range 1 in 3 some 1 here my code : public TextChunks updateFrequencyOfTokenInTextChunks (TextChunks tc) throws CloneNotSupportedException { TextChunks result = (TextChunks) tc.clone(); for (int i =0 ; i< result.arrt.size() ; i++ ){ int j=i+1; if (result.arrt.get(i).compareTwoToken(result.arrt.get(j))== true ) { // help here how to update attribute result.arrt.get(i) // and result.arrt.get(J) = ++ and } } return tc; } Thanks in advandce

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  • Can the size of a structure change after compiled?

    - by Sarah Altiva
    Hi, suppose you have the following structure: #include <windows.h> // BOOL is here. #include <stdio.h> typedef struct { BOOL someBool; char someCharArray[100]; int someIntValue; BOOL moreBools, anotherOne, yetAgain; char someOthercharArray[23]; int otherInt; } Test; int main(void) { printf("Structure size: %d, BOOL size: %d.\n", sizeof(Test), sizeof(BOOL)); } When I compile this piece of code in my machine (32-bit OS) the output is the following: Structure size: 148, BOOL size: 4. I would like to know if, once compiled, these values may change depending on the machine which runs the program. E.g.: if I ran this program in a 64-bit machine, would the output be the same? Or once it's compiled it'll always be the same? Thank you very much, and forgive me if the answer to this question is obvious...

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  • MySql stored procedure not found in PHP

    - by kaupov
    Hello, I have a trouble with MySql stored procedure that calls itself recursively using PHP (CakePHP). Calling it I receive following error: SQL Error: 1305: FUNCTION dbname.GetAdvertCounts does not exist The procedure itself is following: delimiter // DROP PROCEDURE IF EXISTS GetAdvertCounts// CREATE PROCEDURE GetAdvertCounts(IN category_id INT) BEGIN DECLARE no_more_sub_categories, advert_count INT DEFAULT 0; DECLARE sub_cat_id INT; DECLARE curr_sub_category CURSOR FOR SELECT id FROM categories WHERE parent_id = category_id; DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_sub_categories = 1; SELECT COUNT(*) INTO advert_count FROM adverts WHERE category_id = category_id; OPEN curr_sub_category; FETCH curr_sub_category INTO sub_cat_id; REPEAT SELECT advert_count + GetAdvertCounts(sub_cat_id) INTO advert_count; FETCH curr_sub_category INTO sub_cat_id; UNTIL no_more_sub_categories = 1 END REPEAT; CLOSE curr_sub_category; SELECT advert_count; END // delimiter ; If I remove or comment out the recursive call, the procedure is working. Any idea what I'm missing here? The categories are 2 level deep.

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  • Why is T() = T() allowed?

    - by Rimo
    I believe the expression T() creates an rvalue (by the Standard). However, the following code compiles (at least on gcc4.0): class T {}; int main() { T() = T(); } I know technically this is possible because member functions can be invoked on temporaries and the above is just invoking the operator= on the rvalue temporary created from the first T(). But conceptually this is like assigning a new value to an rvalue. Is there a good reason why this is allowed? Edit: The reason I find this odd is it's strictly forbidden on built-in types yet allowed on user-defined types. For example, int(2) = int(3) won't compile because that is an "invalid lvalue in assignment". So I guess the real question is, was this somewhat inconsistent behavior built into the language for a reason? Or is it there for some historical reason? (E.g it would be conceptually more sound to allow only const member functions to be invoked on rvalue expressions, but that cannot be done because that might break some existing code.)

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