C++ :: Pass By Value Arguments Changes Original Copy?
Sep 13, 2013
//This program calls unionLL function which takes list1 and list2 objects of //LinkedList type as arguments also nowhere in the function I had changed List1
//and List2 contents although the list1 and list2 head's and also their next //pointer remain same but the elem or data field is automatically updated to //some garbage value.
#include <iostream>
using namespace std;
typedef int E;
class LinkedList;
class Node {
I have never seen anyone pass by const copy and there probably is a reason. I know that the compiler ignores top level const-ness of function arguments. There are functions which take arguments without manipulating those arguments return the result, for example the C Standard Library funcion double sqrt (double x). The function shouldn't modify it's argument, but it can since the argument isn't const.Take these two functions for example:
double square_root_1(double arg) { arg = 7; // we won't get the desired results return arg * arg;
[code]....
So isn't it better to pass by const copy to make sure that you (or someone else) don't by accident modify the argument? The only disadvantage I see is that it makes the code too verbose.
How to pass arguments from other functions to main. i want to write a program like nano well not exactly like nano editor. I have a function f_read(char* filename[]), and fopen() get filename[1] as file name and *filename[2] as "r" read mode and rest of the code will read from a file.
I want is this char filename[] to main(int argc , char argv[])
I have some trouble with DLL. I created a dll with function
double square(const double * args)
and then in my application defines
typedef double (*MyFunct)(const double *args);
I use LoadLibrary and GetProcAddress to get the function address and cast it to MyFunct. Everything works fine except that when I pass a double *, for example 0x08800350, to the DLL function, the argument becomes totally something else, for example, 0x0aa00460.
I have no clue what happens to the argument value.
I'm trying to merge two files, The Adpoted.txt, and The Originals.txt, into one file, The Big Picture.txt. I'm compiling and getting an insane amount of errors, and am not even sure where to start with them :(. I'm getting errors for lines that don't exist. I suppose I should start with those that do!
#include <iostream> #include <fstream> #include <cstdlib> using namespace std; #define theAdopted "The Adopted.txt" //His family #define theOriginals "The Originals.txt" //Her family #define theBigPicture "The Big Picture.txt" //Our family int merge(ifstream&, ifstream&, ofstream&);
how to combine two bytes (each byte is 8 bits wide) in order to get the original value. I am displaying values(from 0 to 500)sent from my microcontroller on the GUI.I can successfully display values from 0 to 255 as this requires just sending a byte. However sending values from 256 to 500 requires sending two bytes. The problem I am having is that I was unable to re-combine the received two bytes in order to get the original value. Below are my lines of code:
int main( void ) // this is the main function inside the microcontroller { sei(); USI_TWI_Master_Initialise(); Spi_Master_Init(); while(1) // I am using this loop to send 500(111110100) { Transmitt_Receive(244);//this function sends LOW BYTE of 500(11110100) _delay_ms(1000);
[code]....
When I combined the two bytes using the above arrangements, instead of getting 500 my GUI displayed 62708.I got the same result when I used BitConverter.
I have a set of n- dimension point store in `vector< vector<double> >`
ex A[0][1].............[N], and A[0][0] = X, A[0][1] = Y, A[0][2] = Z
and I want to sort the vector of all of the dimension
ex sort X, Y, Z ,.........N in ascending order
ex A[0] = (1,5,3), A[1] = (3,2,1) A[2] = (2,8,4) after sorting index: 0 1 2 A[0] = (1,5,3), A[1] = (2,8,4) A[2] = (3,2,1) original index : 0 2 1
I find that `sort(vector.begin(), vector.end())` can sort it but how can I record the original index with a additional vector?
Is there a algorithm or C++ feature can solve it?
I have tried to solve it with a class wrapper it but I don't know how to write the compare function.
class point{ public: point(int totalLength = 0, int elementLength = 0); vector<vector<double> > pointSet;//store the n-D points vector<double> pointIndex;//store the index }; point::point(int totalLength, int elementLength){ pointSet.resize(totalLength,vector<double>(elementLength, 0)); pointIndex.resize(elementLength); }
I've been taking a C++ class, and for a project we need to do, we have to create a simple quiz show game while putting the high scores and names inside a .txt file. We have lessons we can look at to complete it while learning. But at the end there's always a challenge that we should complete to show that we've actually learned the information. For the challenge, we needed to take the information in the .txt file and reset it to its original information. So say there's 5 people preset that have high scores, then a person plays the game and the program asks if they'd like to reset the list. If the user inputted 'y' or any key that needed to be pressed, the program would reset the .txt to its original information.
This is the code that creates the program.
// Include Libraries #include <iostream> #include <string> #include <fstream> // Include standard namespace using namespace std; // Declare Global Variables int Guess; int Winnings;
[Code] ....
It works how I need it to and there aren't any problems, necessarily, but I want to know if there's any, more efficient, ways of completing this task. Like if there's any already made function of resetting a file.
This is the code that resets the file. As you can see, it just uses the information earlier in the code inside the if statement. Is there any pre-made function or method of resetting a file?
cout << "Would you like to reset the high scores list? (y or n): "; cin >> ask;
I've been given an assignment with the below questions.
1. What is the difference between pass by reference & pass by pointers?
2. What is the use of the initialization list in the constructor?
3. What is meant by a reference & its advantage?
4. Class has a reference, pointer and a const. Is it possible to write the copy constructor & assignment operator overloading funciton? how? ( Since reference is there, I'm not sure on how to write for it)
5. Example for a variable decleration and definition? (I know for function but for variable don kw how)
6. static and const static what is the difference??
I have a method to take a Tile object and make an instances of it based on some data from the original object. Than it is suppose to manipulate the a specific instance and save the results. The first loop through it works but it changes all instance as well as the base.
public static int recurse(int count, Tile[,] b,Huristic h,int check) { if (check==1) { boardState.Add(B)/>; return check; } if (check == 0)
i think i understand both concept. i know that pass by value is that the function receiving those values makes actually a copy of those parameters. Passing by reference makes the variable in the main function to actually see those changes in the other function, instead of a copy, and apply them to the variable in the main function. my question is, why would i pass it by reference if i just can make a return type function.
void query::load_query(const char* filename){ string lines; int count = 0; ifstream file (filename); //READ OPERATION--ONE EXECUTION ONLY if(file.is_open()) {
[Code]...
the 'flds' on the code above has vector <string> data type, i was able to output it using cout but i don't know how to copy its value to another vector <string>...whenever i tried to do that using my own way, the compiled program ended up crashing...
So basically I need to copy vI3Temp into vI3. I assume I can't loop over each element because I haven't sized vI3. So I guess I need some push_back for this. But what code to use?
I have written this code, and at first glance it does what I want, however I am worried that
a) I am overwriting the array that is apssed from chord.getPattern() b) Im getting a memory leak that I want to get rid of, and c) is there generally a /what is the neater way to do it:
Code: uint8_t* ChordBuilder::invert(uint8_t count, Chord chord) { temp = chord.getPattern(); chord.invert(true); //TODO count is how many times to invert. Moves root aswell however
for (uint8_t i = 0; i < count; i++){
[Code] ....
temp is a member variable of ChordBuilder - and is expressed as: Code: uint8_t* temp; I dont want the pattern that chord stores, and passes with getPattern() to change - I fear it is at the moment?
I would rather not use the "new" but I cant think how to get rid of it, however Im not sure where I would need to put the "delete"?
Copy some characters from char * arg to char * first using a loop with specific conditions.
Code:
char * arg; // set arg some string... char first_[25]; char * first; int length; length=strlen(arg); for (n++; arg[n] != '}' || n>=length-1; n++) strcpy(first,arg[n]); // first += arg[n]; I have strcpy(first,arg[n]); but arg[n] is char and strcpy expects char * ;
My goal is to copy only the elements of string 2 that are equal to string 1 into a new string. I tested this idea with an array of integers and it worked, but didn't work for the strings.
Code:
#include<stdio.h> main() { int scan1; char arr1[40] ; char arr2[40] ; char arr3[40] = {'_',.....,'_'}; /*for sake of brevity with post*/ }
The following are the cases when copy constructor is called.
1)When instantiating one object and initializing it with values from another object. 2)When passing an object by value. 3)When an object is returned from a function by value.
I don't understand #2 How can and object be passed by value? when I think of passing object I think of passing by address or reference. explain
I don't understand #3 how can a function returned object by value I think of again passing by address or reference.
