Anonymous
can you any one explain how this code workes?
Anonymous
can you any one explain how this code workes?
this looks like it is someone explaining private inheritance, without actually using inheritance. you want people to explain the explanation itself?
Anonymous
i would suggest reading a book
Anonymous
though i guess the base of the cylinder is called "base" as well
Anonymous
this looks like it is someone explaining private inheritance, without actually using inheritance. you want people to explain the explanation itself?
You mean you would do this instead
class Cylinder : private Circle
or that someone is trying to explain this?
Anonymous
You mean you would do this instead
class Cylinder : private Circle
or that someone is trying to explain this?
ye the Circle was called "base" so i guessed someone was trying to explain what private inheritance looks like.
Anonymous
this looks like it is someone explaining private inheritance, without actually using inheritance. you want people to explain the explanation itself?
But it is member initialization in constructors right?
Anonymous
ye the Circle was called "base" so i guessed someone was trying to explain what private inheritance looks like.
I dont think so. It just refers to the base of the cylinder.
Anonymous
ye the Circle was called "base" so i guessed someone was trying to explain what private inheritance looks like.
Yes I am really confused this based method
Anonymous
though i guess the base of the cylinder is called "base" as well
Aah didnt see this message
Anonymous
Yes I am really confused this based method
it's not a method, it just calls the Circle(double) constructor for the member variable named base
Anonymous
// member initialization
#include <iostream>
using namespace std;
class Circle {
double radius;
public:
Circle(double r) : radius(r) { }
double area() {return radius*radius*3.14159265;}
};
class Cylinder {
Circle base;
double height;
public:
Cylinder(double r, double h) : base (r), height(h) {}
double volume() {return base.area() * height;}
};
int main () {
Cylinder foo (10,20);
cout << "foo's volume: " << foo.volume() << '\n';
return 0;
}
Circle(double r, double h) : base(r), height(h) {}
Here you initialize base which is a circle by calling Circle(double) constructor which initialized the radius of the circle to r. The thing that you see after : is called member initialization list.
Anonymous
Circle(double r, double h) : base(r), height(h) {}
Here you initialize base which is a circle by calling Circle(double) constructor which initialized the radius of the circle to r. The thing that you see after : is called member initialization list.
I have seen this code from online but I am confusing at
Anonymous
Double volume (){return base.area()*height;}
Anonymous
Anonymous
Double volume (){return base.area()*height;}
base is an object of type Circle. You can call Circle's public members using it. Here the constructor of circle initialized the base object's radius to r following which you call base.area() which calls the area member function in Circle. It returns a double value (the area of the base) which is then multiplied by the height of the cylinder to compute the volume of the cylinder.
....
Guys where can I learn making an app with c++ or if u have pdf
Hanz
Guys where can I learn making an app with c++ or if u have pdf
yo, what app do you mean? GUI or TUI?
klimi
Just one of them I dont really know what they are too
it would be better to learn the basics of the language and then learn the graphical libraries
....
it would be better to learn the basics of the language and then learn the graphical libraries
Where can I learn those?
Anonymous
Just one of them I dont really know what they are too
Bryan Cairns' Qt courses on Udemy
....
Bryan Cairns' Qt courses on Udemy
I tried that but it is not that nice do u have pdf or if u would tell me where can I get it?
Anonymous
I tried that but it is not that nice do u have pdf or if u would tell me where can I get it?
which one did you try?
Anonymous
SDL is a nice graph lib
....
OK man do u have PDF?
Nils
void updateProgress(uint8_t percentage) {
if (percentage <= 100) {
barY = (barRect.x2-barRect.x1)/100*percentage;
}
}
Any clue why this does not work? with percentage 100 given the value is not (barRect.x2-barRect.x1)
Anonymous
Nils
Uhm?
Nils
Ohhh
Nils
lol thanks let me try that by casting to float first
Nils
the divide by 100 will truncate digits after the decimal
barY = (float(barRect.x2-barRect.x1))/100*percentage;
It's still not working.
Nils
Yeah, made a float of every single value in the calculation, still same problem.
Anonymous
://
Anonymous
barY = (float(barRect.x2-barRect.x1))/100*percentage;
It's still not working.
add a watch for the expression (float(barRect.x2-barRect.x1))/100*percentage; on your IDE and see what happens
ꍏꈤꀸ
how to evaluate CPU usage by the process while it’s waiting to enter critical section?
right now i have one more thread, which in while(true) each 1s. calculate CPU usage during all execution.
I'm not sure it's the best solution.
BTW, is it ok, that CPU usage is 0% when i'm locking/unlocking mutex?
Nils
how to evaluate CPU usage by the process while it’s waiting to enter critical section?
right now i have one more thread, which in while(true) each 1s. calculate CPU usage during all execution.
I'm not sure it's the best solution.
BTW, is it ok, that CPU usage is 0% when i'm locking/unlocking mutex?
Mutexes are very very optimized, so yes it is
Nils
add a watch for the expression (float(barRect.x2-barRect.x1))/100*percentage; on your IDE and see what happens
Turns out barY was an uint8_t by accident
Arnabjit
How to approach this problem?
https://codeforces.com/problemset/problem/1065/C
ian
Does anyone know why clang -O2 makes my program have this behavior? In my code there is no loop however when using -O2 in clang the program seems to repeat for some reason, but when using -O1 or GCC -O2 it doesn't it does.
IMG: https://postimg.cc/mcGpcwrM
The code is very simple and is the following:
https://paste.opensuse.org/657e1578
clang version 11.0.1
gcc version 10.3.0 (SUSE Linux)
ian
Does anyone know why clang -O2 makes my program have this behavior? In my code there is no loop however when using -O2 in clang the program seems to repeat for some reason, but when using -O1 or GCC -O2 it doesn't it does.
IMG: https://postimg.cc/mcGpcwrM
The code is very simple and is the following:
https://paste.opensuse.org/657e1578
clang version 11.0.1
gcc version 10.3.0 (SUSE Linux)
FreeBSD 13 clang does not cause my program to crash using -O2 (FreeBSD clang version 11.0.1 (git@github.com:llvm/llvm-project.git llvmorg-11.0.1-0-g43ff75f2c3fe))
https://postimg.cc/PPC2qcdN
I assume it has to do with the clang build provided by SUSE ?
olli
FreeBSD 13 clang does not cause my program to crash using -O2 (FreeBSD clang version 11.0.1 (git@github.com:llvm/llvm-project.git llvmorg-11.0.1-0-g43ff75f2c3fe))
https://postimg.cc/PPC2qcdN
I assume it has to do with the clang build provided by SUSE ?
You should fix your warnings, there are multiple issues in your program.
scanf stores length + 1 characters because the string has to be null-terminated, hence 8 bytes are not enough to store "DDMMAAAA"
PS
How to find largest subsequence of array??
Anonymous
How to find largest subsequence of array??
You dont have to find anything. Just return the array.
Anonymous
How to approach this problem?
https://codeforces.com/problemset/problem/1065/C
Sort the array of blocks on height from smallest to tallest and use greedy programming
PS
It has a condition too
PS
That sum of elements in subsequence must be greater than 0
Anonymous
That sum of elements in subsequence must be greater than 0
You should mention that as well when you ask a question.
Does the sub sequence elements need to be in the same order as in the array I.e. should they be contiguous elements?
Anshul
If I make a pointer of type list. Then will it be able to access the elements of list.
(List I'm referring is c++ stl)
fun(list * start, list* end)
{
List *p;
for(p=start;p!=null;p=p->next)
.....
...
Here is it possible to do
p->next
will p not be pointing at the head of the list. Or p will be pointing at the first node in the list
Anonymous
If I make a pointer of type list. Then will it be able to access the elements of list.
(List I'm referring is c++ stl)
fun(list * start, list* end)
{
List *p;
for(p=start;p!=null;p=p->next)
.....
...
Here is it possible to do
p->next
will p not be pointing at the head of the list. Or p will be pointing at the first node in the list
No. std::list does not have a next method or a public data member with that name and hence p->next will be a compiler error.
You should use std::list<type>::iterator (or the const_iterator) instead
Anshul
Okay
Anonymous
If I make a pointer of type list. Then will it be able to access the elements of list.
(List I'm referring is c++ stl)
fun(list * start, list* end)
{
List *p;
for(p=start;p!=null;p=p->next)
.....
...
Here is it possible to do
p->next
will p not be pointing at the head of the list. Or p will be pointing at the first node in the list
p will not be pointing at the first element. Instead it will be pointing to the data structure std::list<type> which is not the same as the list of the elements it refers to
Anshul
P will be pointing to an object of list?
So by Using arrow operator with p, I can only access head of list right?
Anonymous
P will be pointing to an object of list?
So by Using arrow operator with p, I can only access head of list right?
No. Suppose say you do this:
void fun(){
std::list<int> a;
//populate a
auto p = &a;
}
Here a is allocated on the stack. But when you populate the list, the elements themselves will be allocated on the heap.
So p will be pointing to the data structure on the stack and not to the elements on the heap. You have to understand the difference clearly here.
Anshul
No. Suppose say you do this:
void fun(){
std::list<int> a;
//populate a
auto p = &a;
}
Here a is allocated on the stack. But when you populate the list, the elements themselves will be allocated on the heap.
So p will be pointing to the data structure on the stack and not to the elements on the heap. You have to understand the difference clearly here.
Yeah thanks. So will there be any use of creating such pointer.
As we can't access anything using pointer p
Anonymous
Yeah thanks. So will there be any use of creating such pointer.
As we can't access anything using pointer p
There are not many uses for creating a pointer to a STL data structure in Modern C++.
But if you have a pointer, you can still access the list's public data members using that pointer. You can also pass this pointer to other functions instead of passing the list data structure itself (a reference should be preferred however).
Anshul
If I pass list like this
Fun( list a)
{}
Main ()
{
List<int> b;
Fun(b);
}
Here any changes made to a will it reflect to b as well?
Anshul
You mean I should pass like this
Fun (list &a)
{}
instead this
Fun (list *a)
{}
Anonymous
If I pass list like this
Fun( list a)
{}
Main ()
{
List<int> b;
Fun(b);
}
Here any changes made to a will it reflect to b as well?
No. Here you are passing a copy and changes to the copy wont be reflected in the original list.
Anshul
Anonymous
You mean I should pass like this
Fun (list &a)
{}
instead this
Fun (list *a)
{}
Yes. The first method is preferred. There are other ways of passing a list like passing an iterator range or using ranges library (or std::ranges if you use C++20)
Anshul
You mean I should pass like this
Fun (list &a)
{}
instead this
Fun (list *a)
{}
And in both cases changes will be reflected in the original list?
And why first one is preferred? Is it because first one doesn't create a new memory space
Anonymous
And in both cases changes will be reflected in the original list?
And why first one is preferred? Is it because first one doesn't create a new memory space
Yes changes will be reflected in both.
The first one is preferred because generally when you use raw pointers, it is not clear at the call site if the caller/callee should free the memory associated with the pointer. Because raw pointers are seldom needed in Modern C++, the second method should not be used.
Evans
Anyone with Full C resources?
Good person
Anonymous
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klimi
i need help on c programming on homework please contact me ! i can pay thank you ! its a business for you, you can earn money ! 😀
no.. no... no... :( why you have to do this? why don't you atleast comply with the rules?
Anonymous
hey, guys
following the best practices, should I write:
char* string
or
char *string ?
Anonymous
hey, guys
following the best practices, should I write:
char* string
or
char *string ?
Just follow the style already existing in the code base.
If it is a new code base and if you are in the habit of declaring multiple variables of the same base type on a line choose
char *str.
If you follow the practice of declaring/defining only one variable on a line then either is good.
Anshul
What can be the reason for this
Terminate called after throwing an instance of std::logic_error
Anshul
terminate called after throwing an instance of 'std::logic_error'
what(): basic_string::_M_construct null not valid