I'm asking how to create a function with default parameters with the possibility to init the parameters that you need.
Code Example :
#include <iostream>
int func(int a = 1, int b = 2, int c = 3, int d = 4) {
return a + b * c / d;
[Code] .....
I have developed an application in C++ that creates some text files in a directory chosen by the user.
How can I ask the user set a Default Directory Path (and some other default parameters) so that she doesn't have to enter the same data in the GUI everytime the application is run.
The application has been developed using Qt Creator.
[URL] ....
#include <iostream>
#include <vector>
void f(std::vector<int> const &v, std::vector<int>::const_iterator it = v.end()) {
} int main() {
f({}); }
prog.cpp:4:73: error: local variable ‘v’ may not appear in this context
void f(std::vector<int> const &v, std::vector<int>::const_iterator it = v.end())
Why is this not allowed? (I mean, what is the reasoning for defining the standard this way?)
In C++14/C++17 we will have a unified way to represent end iterators without an instance of the container, but currently I just have to hope my implementation accepts a default-constructed iterator as an end iterator.
In the thread "Making a argument optional to function", it is stated that to set default values for arguments of a function you can simply do so in the function definition, like:
int myfunc(int a, int b, int c=3) {...}
This then automatically puts c to 3 in the function body if a call like myfunc(1,2); is made, if I understood correctly. However, this does not seem to hold for class functions. For example, something like:
class classy {
public:
int class_func(int, int, int); // class function prototype
}
int classy::class_func(int a, int b, int c=3) {...}
fails to compile. What I would like is to be able to call class_func outside of this class (by including it as a header in another macro), optionally specifying c. If c is not specified in the call, it should use a default value.
Last night I was trying to see if is possible to multiply one number to another without using any given function(like pow) or the multiply sign or whatever. Just using addition and subtract signs (+and -) with a for loop. It worked.
Now I am trying to understand if is possible to elevate one given number (inserted by the user) to another number without using again any function or the multiply / divide/ etc functions. Just add and subtract functions.
I have an advanced data namespace in which I hope to be able to read a data variable of any type and transfer it's bytes into another type of a multiple size.
i.e.
char[4] -> int;
int -> short[2];
short -> char[2];
char[2] -> short;
but I'm having some trouble, I get the following errors (because as a template it must compile from start)
template<typename T1, typename T2> void stepBytes(UCHAR size1, UCHAR size2, T1 in, T2& out){
if(size1 == 0 || size2 == 0)
return;
if(size1 % size2 != 0 &&
size2 % size1 != 0)
[Code] ....
So, why's this error appearing?
i heard that it was int but later it is deprecated , so at present what is the default return type of a function ?
View 4 Replies View RelatedIn my program I created three separate return functions. Each function is labeled:
int boxes(int x, int y);
int leftOver(int x, int y);
double avgItemsShipped(int x, int y, int z);
Is it bad programming practice to use 'x' and 'y' in all of my functions? Should I use the this keyword inside the function? We use this often in my Java class and I know it exists in C++, but I haven't actually seen it used (or used it myself yet).
What does collection of parameters as argument of a function in C mean? Also any place I can refer to find those parameters?
Googling gives me Parameters and Arguments But not really sure whether that is what is needed.
So in this function it is already passing the array into the function but the thing is one parameter being passed into the function and if so how do I go about passing 3 arrays as parameters into the function? Also the program only asks for a user entry of hours for three different cars so why would there be a point in making two additional arrays to be passed into the function?
#include <iostream>
#include <iomanip>
using namespace std;
//passing array into function
double calculateCharges(double hours[], int HoursArrayLocation);//call function
[Code] ....
So I was reading my book and it listed this piece of code. The first piece of code is in the book and the 2nd is just my test on the piece of code. I am curious as to why in the functions parameters there is a reference to aString. I've noticed that removing it has no affect on the outcome of the code.
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
bool isPalindrome (string & aString) {
[Code] ....
So I'm writing a data structure from scratch as part of a university assignment in c++, and I have to write an iterator for it. The problem involves comparison between constant iterators and normal iterators, and I'm going about it in this way: I wrote a constructor of normal iterator which takes a const iterator as its only parameter, hoping that the comparison operator between two normal iterators will be enough:
btree_iterator(const_btree_iterator<T>&conv):_target(conv._target),_index(conv._index),_last(conv._last){}
(and somewhere else)
template <typename T>
bool operator!=(btree_iterator<T> one,btree_iterator<T> other){
return !(other == one);
}
and I'm testing it in this way:
btree<int> bl(5);//the data structure
auto iter = bl.begin();
iter != bl.cend(); //trying to compare iterator with const iterator
but apparently this is wrong, since the compiler tells me something along the line of "no function 'operator!=' which takes ......" It seems the constructor is alright, since the following works:
btree<int>::iterator i(bl.cend());
Am I getting something fundamentally wrong about it? How is this functionality actually implemented in C++ library containers like vector?
I am creating code for a group project in my class. All my group members made a header file with an object in it with their functions. One of the functions in my partner's code uses a data member of mine in the function, so she has the function parameter a object of my object. (This isn't the code but for example)
class B {
friend class A;
void displayAthing(A object) {
cout<<object.thing<<endl;
}
I have this when I call the function in the cpp file
int main() {
A object;
B b;
b.displayAthing(object);
return 0;
}
However, when I compile, it gives me an error that the function does not take 1 arguments.
I noticed that when using variadic functions, if I pass the va_arg() as parameter to a function, the parameters get passed in reverse. Is that expected?
For example, the following code outputs
Code:
1 2
2 1
Code:
#include <iostream>
#include <stdarg.h>
void foo_func(int v1, int v2)
{
std::cout << v1 << " " << v2 << std::endl;
[Code] .....
Need setting up counters for this program which should
Given a file of text, assume that
a "word" is 1 or more consecutive, non-whitespace characters
a "sentence" is a series of words terminated by either a period, exclamation point, or question mark
Design a C++ program (using functions/passing parameters) that will
-interactively prompt for and read the name of an input file
-interactively prompt for and read a string to search for
-open the input file (using an input filestream variable) and with one pass through the file
-count the number of "words" in the file
-for each word, make sure all letters, except the first, are lower case - leave the first character unchanged
-count the number of "sentences" in the file
-count the number of letters in the file (A-Z,a-z)
-count the number of consonants in the file (consonants are letters that are not vowels - the vowels are: a, e, i, o, u, A, E, I, O, and U)
-count the number of nonwhitespace characters in the file that are NOT letters
-count the number of times the search string is found in the file (must be an exact match) - search for matches AFTER upper case letters have been coverted to lower case
Is there anyway we can return 2 values from a called function. Example
Code:
float xxxx(float a, float b, float c, float d)
{///
///
///
}
void xxx() {
int e,f,g,h;
////
////
xxx(e,f,g,h);
}
So if I want for example a+b and c+d, can i return those 2 answer? I don't think its possible since I am new into C programming.
I have this code:
#include <iostream>
#include <vector>
#include <map>
#include <string>
using namespace std;
[Code]...
and it does not compile.
The error is:
test.cpp: In function ‘int main()’:
test.cpp:20:30: error: no matching function for call to ‘func1(std::vector<int>&)’
test.cpp:20:30: note: candidate is:
test.cpp:8:45: note: template<class T, class U> std::map<T, T> func1(U)
test.cpp:8:45: note: template argument deduction/substitution failed:
test.cpp:20:30: note: couldn't deduce template parameter ‘T’
I'm using the Visual C++ Express 2008 and i need to pass as parameters to a function characters coded in UTF 8. My environment is Windows 7. The editor of the VC++ write in UTF 8 or UTF 16? If it writes in UTF 16 how can i change it?
View 2 Replies View RelatedI have been experimenting with variadic templates with the aim of caching a call to a class method by storing away the object pointer, method pointer and parameters. I've actually had some reasonable success but have now hit a stumbling block. I now wish to wrap my parameters in a simple template class when I cache them. My success is as follows:
Using variadic template functions to store these pointers and paremeters;
I'm able to pass a method pointer and unwrapped parametersI'm able to pass wrapped parameters on their own.I'm NOT able to pass a method pointer and wrapped parameters I set up a little prototype project to demonstrate the issue and added comments above the function calls to indicate the compilation results. Here is the code:
Code:
#include "stdafx.h"
//////////////////////////////////////////////////
// Basic class with a simple method
//////////////////////////////////////////////////
class MyClass {
public:
char Method( int i, float f ) {
return 'A';
[code]....
But I'm convinced it should take three arguments, the method pointer and two wrapped parameters. Visual studio even suggested it should as shown below:
What would be the correct way to call a function within main that has file pointer parameters?
function prototype: Code: void CalculateBoth(int num1, int num2, int*sumPtr, int *diffPtr);
I'm trying to write a simple Delegate class with a Bind() and Invoke() function. For now it only needs to support a void class function with no parameters. I've searched around and found quite a few exmaples, though, those class are heavily templated and I lose track trying to simplify it.
So far my code is following:
Code:
#include <windows.h>
class Test {
public:
void DoSomething() {
MessageBox(NULL, L"Test::DoSomething!", NULL, 0);
[Code] ....
The part I am having difficulty with is assigning &Test::DoSomething to the m_Callback variable.
&tObject::DoSomething works, yet _Callback which I pass &Test::DoSomething to does not work.
Also, why does the following line work:
Code:
m_Callback = &Wrapper<tObject, &tObject::DoSomething>;
When wrapper is like:
Code:
template<class tObject, void (tObject::*Func)()>
void Wrapper(void* Object)
Should it not be Wrapper<class-typename, parameter-1>(parameter-2) // This currently creates an error
Following is the code snippet
Code:
[COLOR=white !important]?
1
2
3
4
5 char str1[]="Bombay";
char str2[]="Pune";
char *s1=str,*s2=str2;
while(*s1++=*s2=str2);
printf("%s",str1);
Output of this code comes out to be Pune
But according to me output should be puneay.
Pune should be copied in place of Bomb.and rest should be as it is.
[/COLOR]
I have a problem. I want to set pointers to a default value for both 32 bit and 64 bit compiles. The 32-bit version works as:
enum constants { UNDEFINED = 0xDeadBeef }
if ((unsigned long)ptr == UNDEFINED)
but I can't seem to extend this to 64-bits. I've tried
#if __SIZEOF_POINTER__ == 4
enum constants { UNDEFDATA = 0xDeadBeef };
}; // enum constants
#elif __SIZEOF_POINTER__ == 8
enum constants { UNDEFDATA = 0xDeadBeefDeadBeef };
#endif
with:
if (ptr == UNDEFINED)
but get a message saying the '==' is undefined (I understand this)
Is there any way to setup so that I can change the size of my constants so that the comparisons will always work correctly? I've tried a 'typedef' but the compiler complains at
'typedef unsigned long long ADDR' // won't accept, and
static const SlipCellBase * const TEMPORARY = (SlipCellBase&)0xFFFFFFFFFFFFFFFF; // illegal conversion
enum doesn't work (because it's an int?)
First I wrote a Binary-tree class to draw a binary tree on the window. The nodes were small circles. Then I become wanted to change the shape of the nodes from circles to triangles by another class, Binary-tree-derived which is derived from Binary-tree class. I wrote the below code to do the job but I get two errors about constructors. First, code:
/* The binary-tree class, one of the topics that has been said in Programming Principles and Practice using C++ book by Biarne Stroustrup.
This code is written by R Abbasi (s.rabbasi@yahoo.com) */
#include <Simple_window.h>
[Code].....
Errors are:
Error12error C2512: 'Binary_tree' : no appropriate default constructor availablec:userscsdocumentsvisual studio 2012projects est_1 est_1 est_1.cpp91
13IntelliSense: no default constructor exists for class "Binary_tree"c:UsersCSDocumentsVisual Studio 2012Projects est_1 est_1 est_1.cpp91
How to create default arguments in C? Is there any way to make default arguments ( i mean any alternative for them).
View 5 Replies View RelatedHow do you write a default constructor?I need to use a default constructor that will initialize the data members:
- salesPerson to “Unknown”
- noOfWeek to 13
- amount to point to an array of thirteen 0.00s.
This is my weeklysales class
class WeeklySales {
char* salesPerson;
double* amount; // Pointer to an array
int noOfWeek; // Size of the array
};
Here's my attempted code:
//default constructor
WeeklySales (){
salesPerson="Unknown";
noOfWeek = 13;
amount = 0.00;
}
