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Type: Posts; User: wolle

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1. ## Thread: simple rendering

by wolle
Replies
3
Views
181

### Re: simple rendering

When I started Windows programming in C++ I used a GUI (Graphical User Interface) package called Win32++. There are several sample applications included. I picked the one I thought looked most like...

by wolle
Replies
1
Views
211

The brute force solution is to generate all possible triplets (corners of a triangle) and select those that form a right triangle.

This solution can be improved. By geometric reasoning it is...
3. ## Thread: How do I write a recursive golden ratio?

by wolle
Replies
3
Views
296

### Re: How do I write a recursive golden ratio?

It looks like you're trying to use the fact that you get the golden ratio if you divide two consecutive numbers in the Fibonacci sequence?

Since I don't know any Python I have to cheat and search...
4. ## Thread: virtual function in derived class

by wolle
Replies
6
Views
479

### Re: virtual function in derived class

When you have virtual functions in a base class you must put in a virtual destructor too. It's enough to have it in the top base class if there is an inheritance chain (like you have). If it's not...
5. ## Thread: implicit conversion in derived classes

by wolle
Replies
7
Views
755

### Re: implicit conversion in derived classes

The first case is fine. It's called an upcast. The base class pointer will point to the derived object and access it as if it were a base object. The other way around is called a downcast and it has...
6. ## Thread: Set of Unique pairs

by wolle
Replies
32
Views
1,644

### Re: Set of Unique pairs

Well, it turns out I was on the right track after all so I restore the solution and continue.

I had the idea that a pair (i,j) can be viewed as a square on a 6 by 6 chess board. We place 6 rocks...
7. ## Thread: Set of Unique pairs

by wolle
Replies
32
Views
1,644

### Re: Set of Unique pairs

Yes I've realized that so I removed my failed solution.

by wolle
Replies
4
Views
393

cin >> n >> q;
int ar[n];

I think this is the error. You cannot declare a C array to be of a certain size n by reading n at runtime. Instead n must be available at compile-time already. It...
9. ## Thread: Set of Unique pairs

by wolle
Replies
32
Views
1,644

### Re: Set of Unique pairs

The purpose of the hash table was to store pairs (i,j) you have encountered so you can check later whether you have encountered them before.

The purpose of the 2-dimensional 6 by 6 int array is to...
10. ## Thread: Set of Unique pairs

by wolle
Replies
32
Views
1,644

### Re: Set of Unique pairs

I've shared a lot already.

I think it's your turn now.
11. ## Thread: Set of Unique pairs

by wolle
Replies
32
Views
1,644

### Re: Set of Unique pairs

In C I would be less general and replace the hash table with a 6x6 2-dimensional int array.

Instead of the numbers 1 to 6 I would use 0 to 5.

The array is initially set to all 0. To indicate...
12. ## Thread: Set of Unique pairs

by wolle
Replies
32
Views
1,644

### Re: Set of Unique pairs

Sure, the C++ standard library (STL) offers both a function to generate permutations and a suitable hash table.

https://en.cppreference.com/w/cpp/algorithm/next_permutation...
13. ## Thread: Set of Unique pairs

by wolle
Replies
32
Views
1,644

### Re: Set of Unique pairs

I seems like all numbers 1 to 6 must always be present in each set. If means if you start with this set,

(1,2)(3,4)(5,6)

you can generate all possible variations of that set simply by...
14. ## Thread: cin isn't blocking

by wolle
Replies
12
Views
824

### Re: cin isn't blocking

Do all user input/output from the main thread.

Then set up a message system, that is some way to pass information between threads.

If you do this you're on solid traditional ground and don't...
15. ## Thread: cin isn't blocking

by wolle
Replies
12
Views
824

### Re: cin isn't blocking

Yes I bet this is the problem. The OP is not reading the standard input from inside the main thread.
16. ## Thread: unexpected behavior of integer variable

by wolle
Replies
21
Views
1,359

### Re: unexpected behavior of integer variable

You don't have to skip C++ altogether. You can still use elements of C++ to your advantage without taking on the full modern C++. As I mentioned in #11, one example is the standard STL data...
17. ## Thread: unexpected behavior of integer variable

by wolle
Replies
21
Views
1,359

### Re: unexpected behavior of integer variable

I googled for Arduino UNO,

https://store.arduino.cc/arduino-uno-rev3

and when writing code for devices like this I would say C++ may be overkill.

I would concentrate on the C part of C++. It...
18. ## Thread: unexpected behavior of integer variable

by wolle
Replies
21
Views
1,359

### Re: unexpected behavior of integer variable

That line is wrong in two ways. It should be,

if (i == 0) numstr.append("0");

= is an assignment, == checks for equality.

There is a standard function to_string you can use,
19. ## Thread: Should I go for QT?

by wolle
Replies
5
Views
523

### Re: Should I go for QT?

If you want C++ then I suggest you go for Qt. It's not just a GUI but also an application framework. You'll have to check out the contents of the framework to find out whether it has what you need....
20. ## Thread: std::string trim

by wolle
Replies
6
Views
3,233

### Re: std::string trim

What about Boost? It's well tested and has the status as almost STL.

https://www.boost.org/doc/libs/1_72_0/doc/html/string_algo.html

I'm not a lawyer but my impression is that the Boost licence...
21. ## Thread: vb6 will and VC98 C++ won't

by wolle
Replies
9
Views
559

### Re: vb6 will and VC98 C++ won't

Sure, rounding!
22. ## Thread: bizare compiler error assigning a value to a string (expected constructor, etc)

by wolle
Replies
8
Views
682

### Re: bizare compiler error assigning a value to a string (expected constructor, etc)

I do this a lot. I post a section from my production code as an example. It's a conversion function called toElement that turns atom names in the form of strings into internal counterparts.

Since...
23. ## Thread: sort vector of struct

by wolle
Replies
7
Views
599

### Re: sort vector of struct

I don't think the call to fill is strictly necessary since when the vapp vector is constructed it will be filled with N default constructed app structs whose members will be initialized to the...
24. ## Thread: bizare compiler error assigning a value to a string (expected constructor, etc)

by wolle
Replies
8
Views
682

### Re: bizare compiler error assigning a value to a string (expected constructor, etc)

There are restrictions as to what kinds of code you can put at different places.

If you put the assignments inside a function the code should compile. This function then obviously must be called...
25. ## Thread: sort vector of struct

by wolle
Replies
7
Views
599

### Re: sort vector of struct

Yes you're right, and I suppose the OP would've got a compiler error if they weren't allowed.
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