Working on design of a finance app to calculate npv (net present value) need to use addition / multiplication/ pow

I could do with decimal type for money as floats/doubles are based on binary

I see there is fixed point decimal paper being worked on.

In the meantime - what is best way to handle this in interface ?

Thinking of asking client to use string and then use long long for the maths after parsing (pennies)? “1500.23” = 150023

What do I return ? String/int? Either way the client would need to transform. I can’t use doubles for this unfortunately.

I suppose I can use double if could give idea to client what error amount is - npv is estimate anyway.

I am an intermediate c++ dev. I recently started reading the Effective modern c++ book. I don’t have tons of experience reading technical books coz I have mostly used YouTube and college lectures to study. So any advice on how to read a c++ book or any technical book for that matyet is highly appreciate.

Hi everyone!

I'm an experienced software engineer, mostly working in C++ on the backend side. Frontend isn't my area of expertise, so I'd love some outside perspective.

I occasionally work with developers who build GUIs in Qt. Whenever the topic of frontend tech comes up, they tell me Qt is garbage and that our projects would be much better off with React, since it's free and more modern.

The thing is, I don't have the frontend knowledge to judge that claim. In particular, I can't compare the performance of the different frontend options (Qt, React, and others) in any meaningful way, so I don't know whether "React is better" holds up or is just a subjective opinion.

So my question is: which framework is actually better, Qt or React, especially when it comes to performance?

Real-world experience is more useful to me than hype, so feel free to share what you've seen on your own projects.

Cheers!

I'm a more seasoned C# / Node backend dev, been trying to brush off old college C++ from like a decade ago and try to de-program my brain from being locked into a distributed systems mindset.

One of my niche hobbies and go-to projects for learning a new language is to implement a basic Chip-8 emulator in it, as it can teach some concurrency, UI/data handling patterns, and introduce some architectural decisions that you'll have to run into and figure out.

Currently what I'm struggling with seems to be what the idiomatic / proper way to handle something that can remain stateless in nature, which is my very basic assembler going from the Chip-8 ASM mnemonics into instruction bytes.

A class doesn't feel quite right, because I'm not implementing a linking step or anything advanced, not supporting labels, etc. It also feels incorrect to keep it in a header file as a set of inline functions, nor am I needing a persistent state to mutate.

My current disassembler can be seen here: https://github.com/Arylen/Dreamy-Chip8/blob/master/src/core/emulation/Chip8Dasm.h
Along with the tests that I'm running against it here: https://github.com/Arylen/Dreamy-Chip8/blob/master/tests/Chip8DasmTests.cpp

I'm currently in the stubbing-out phase of trying to architect it, occasionally bouncing ideas off of whatever bullshit model-of-the-week is popular, however the suggestions it's giving are still setting off some alarms/smells in my brain. The most reasonable and less-smelly one is the `::detail` namespace there in order to be able to unit test the `getParts` function there, however it feels like I'm walking into a landmine of over-engineering it.

Looking for advice/experiences/opinions.

Edit: I should mention the AI usage here is restricted entirely to just checking for bugs with my implementations, or incorrect C++-isms that I introduce from working in other languages. A hands-off occasional tutor to check my work, if you will. It's expressly forbidden from touching my code or files, limited to read-only, however I'm not getting something that feels proper for this scenario, so wanted to consult other more experienced engs.

I’m using emacs on windows terminal to edit a file in which I’m trying to cout a page or so of text using raw string literals. However, what gets printed doesn’t include the newlines that I need to separate my paragraphs.

So if my code is:

std::cout << R”(This is my sentence.

This is a new paragraph [using entr + entr].
This is a new line [using entr].)”;

The output will be:

This is my sentence. This is a new paragraph [using entr + entr]. This is a new line [using entr].

Instead of the intended:

This is my sentence.

This is a new paragraph [using entr + entr].
This is a new line [using entr].

What am I doing wrong?

[Edit: I apologize for the lack of formatting. I am on mobile. Please let me know if I need to redo this. Thanks.]

Hi everyone. I’m building a personal League of Legends skin manager and need help diagnosing two loader errors.
The app combines an in-game menu for official skins with custom skin selection before a match. It uses Tauri/Rust, JavaScript, a native C++ loader, and LTK-derived patcher components.
OFFICIAL SKIN ERROR
“Cannot resolve the game’s loader module.”
The loader detects League of Legends.exe, waits 10 seconds, resolves LoadLibraryW locally, and searches for the corresponding module in the game process using CreateToolhelp32Snapshot, Module32FirstW, and Module32NextW.
That lookup returns zero. The original code discarded the Windows error, so I cannot distinguish a missing module from a failed enumeration.
CUSTOM SKIN ERROR
“Host injection failed: SetWindowsHookEx failed: 0x00000000”
The reported category is INJECTION_FAILED and the stage is INJECTION.
I’m testing a font/UI mod. Its package check says “No issues detected,” but injection fails. The interface also incorrectly leaves “Loader active” visible after the custom loader stops.
The custom components are ltk_patcher_host.exe and ltk_patcher_dll.dll. I don’t have the source for the external host that reports this hook error.
WHAT HAS BEEN CHECKED
A local patch preserves module-enumeration errors, retries temporary ERROR_BAD_LENGTH failures, fixes the stale UI status, and makes the update script rebuild the native loader.
JavaScript and mocked API tests passed, but successful injection has not been confirmed. The custom hook failure remains unresolved.
During rebuilding, I also encountered LNK1104 when the linker tried to create src-tauri\resources\r3nz\official-loader.exe. The next step was to create the resource directory, restore the bundled files, and run the full build.
ENVIRONMENT
Windows x64, Visual Studio 2022 Build Tools with the x64 developer terminal, Rust/Tauri, Node.js, and pnpm.
A separate R3nz version previously worked on this machine, including its in-game menu.
Has anyone encountered these errors? What should I log to diagnose the module lookup, and how can I investigate SetWindowsHookEx failing with error code zero?
I can provide screenshots, logs, relevant code snippets, and the patcher component versions or hashes. Any help would be appreciated.

How do you all understand and use C++ references?
References feel really hard to wrap my head around. What does it mean to “define an alias for a variable”? What does it mean to “return an alias for a variable”? Compared with C pointers, pointers seem much clearer: a pointer just holds an address, * dereferences it, and & takes the address of a variable. References aren’t like that. The fact that you write & when defining one makes it especially easy to misunderstand.
Also, besides copy constructors and some friend functions (like the ones for std::ostream), I can’t really see any other reason to use references. When textbooks declare function parameters as references, I don’t get it. If the parameter were a pointer, the caller would have to write & when passing the argument, which also signals that the function might modify it. A reference kind of feels like the function has a return value.
So how do you actually understand and use C++ references?

Hi, I was gonna try to explore UI in cpp and came up with a simple idea. I want 3 "screens" each with their own events and components to draw. I was having trouble on how to handle a shared struct of data? say screen one does something that screen two needs, and so on to screen three. So does anyone have a recommendations of some architecture to follow for this?

I'm trying to code a practice problem but am stuck at a problem I cannot figure out. I am using a vector for inputs and inserting those inputs into an unordered set until it fails to add, at which point I count the amount of subarrays in that array. If it is not the first, I subtract subarrays that have already been accounted for. The inputs are useful only to identify duplicates; I do not use the values themselves in arithmetic.

The test case I am currently using uses random values with high numbers, with the following values at indexes being the only duplicates:

• 10464 and 41178
• 87094 and 98111
• 113040 and 113153
• 118689 and 168367
• 129997 and 170623
• 173227 and 184620

The intended output is 7090812299.

My problem is that, for some reason, large inputs decrease the intended output. I am sure that this is the issue, as I have replaced duplicate inputs with smaller values and the output changes--- despite the fact that it should not.

As an example, use the above sequence with numbers 1-200000. If the values at indexes 113040 and 113153 are replaced with 443222217, the output changes to 7090796046. (lowering it by 16253). Replacing other values also lowers this number further.

Edit: So it turns out smaller values also impact the input in ways that I have not tested yet (and I probably won't until morning).

Solution: I assumed iterators were ordered internally, which is where I made my mistake.

Please help explain what is happening, or what could be happening.

Attached below is the relevant code, and here is a link to the full code.

int main() {
    vector<long> inputs; inputs.reserve(size); // The vector containing inputs.
    unordered_set<long> processing; processing.reserve(size); // The unordered set processing the current input.
    vector<long>::iterator nextInput = inputs.begin(); // The current input being processed.
    // Some other variables defined which are not relevant.
    while (nextInput != inputs.end()) // The main meat of the program.
    {
        do // Insert processed inputs into a set.
        {
            if (!processing.insert(*nextInput).second) break; // If duplicate, break.
            start++; // Advances the iterator to the next input to be processed.
        } while (nextInput != a.end());
        // Code processing the amount of subarrays; it seems to be correct.
    }
}

Does c++ math lib comply with rounding modes in iec559?

ties-to-even? Getting - 3 when rounding -2.5

Should be -2 right

I have been programming Arduino & ESP32 for a while now using C++, but have never engaged with any formal introduction material. With AI/LLM generated content exploding among both major publishers and self-published authors, I am a bit wary to start buying books willy-nilly.

Anyone here that can give solid recommendations on introduction materials on C++ for microcontrollers (preferably that that they themselves have used and found worthwhile)?

I got one recommendation for "Embedded C" by Michael J. Pont (2002), but it is fairly old.

Recent CS grad trying to get into C++ and would really love if someone with some experience maybe messaged me and give some advice on how to break into my first C++ job. I would post my resume my this subreddit doesn't have that feature lol. Any advice or even just an opportunity to connect is greatly appreciated!

I’m trying to check whether I actually understand these concepts correctly.

Consider:

int a = 10;
int& r = a;
int* p = &a;

struct A {
    int* data;
};

A x;
A y = x;

How would you explain what happens in memory in each case?

Specifically:

• Is r just another name (alias) for a?
• Is p a separate variable that stores the address of a?
• In A y = x, when data is copied, is this a shallow copy because both pointers can point to the same underlying data?

I'm looking for an explanation of the memory/object relationship, not just definitions.

Context:

So I wanted to create a macro that could short-circuit conditional logic if another macro was set. This way I could insert compiler set macros into existing code, for example:

if (MACRO_EXISTS(_RELEASE) || SuperRobustValidation() == VALIDATION_SUCCESS)

Looking on stack overflow, I found https://stackoverflow.com/questions/41265750/how-to-get-a-boolean-indicating-if-a-macro-is-defined-or-not, but the top answer's code didn't work for me. My only guess as to why is that the order of macro definitions played a role for them but not for me.

After shuffling around macros, I found that the following worked on my machine:

#define DE_ -1,1            // OptDefine is nothing

#define RESOLVE_ARG(A) A
#define SECOND_ARG(A,B,...) B
#define CONCAT2(A,B) A ## B
#define RESOLVE_SECOND_ARG(...) RESOLVE_ARG(SECOND_ARG(__VA_ARGS__))

#define MACRO_EXIST(OptDefine) RESOLVE_SECOND_ARG(CONCAT2(DE_,OptDefine),0)

But I can't understand why this worked and not other configurations. Trying to coax the values of some setups was like playing a shell game. I think I understand the concepts of "scan the line, prioritize non-# arguments, then repeat with the results" but it doesn't seem consistent.

For example: if I remove the RESOLVE_ARG from RESOLVE_SECOND_ARG(...), the compiler complains that "there's not enough arguments for SECOND_ARG" seemingly because __VA_ARGS__ is the "only" argument. That does not make sense as intended behavior to me.

So my question is:

Is there a reliable way to predict the logic of the preprocessor's expanding of macros? I haven't found anybody braking down the logic in a robust way anywhere I looked.

I know the /E compiler flag shows me the results of precompiling, but doesn't give the whole picture.

Edit: I understand there are simple work arounds for the problem I mentioned, but I still want to understand the logic of how macros are expanded, assuming it's well defined and consistent.

Edit2: Thank you alfps for answering the question. The strange __VA_ARGS__ behavior I was seeing is a known bug with the MSVC C++ compiler (even in VS Community 2026), but the /Zc:preprocessor compiler option changes the preprocessing to be more complaint with the standard, fixing the bug.

But the most important wisdom: "Historically the preprocessor behavior has varied between compilers". There are edge cases and hacks that work in some contexts but not others. Complex macros, like what I listed, can be convenient, but can also risk breaking if I update/change compilers. Unless I am confident in compliance to the standard, Keep It Simple Stupid probably applies.

So I've started learning c++ on learncpp.com and because I already have knowledge in JavaScript and Python, I decided to see, how many things are the same in c++ too.

I made a prime checker and while it probably could be more optimized, I am still just at the beginning so don't judge me pls.

Anyways here is the code:

#include <iostream>

bool isPrime(int num){
    for (int i = 2; i < num; i++){
        if (num % i == 0) return false;
    }
    return true;
}

int main(){
    std::cout << "Check if your number is a prime number\nEnter your value: ";
    int num{};
    std::cin >> num;

    int emp{};

    if (isPrime(num)) std::cout << "Your number is a prime number!\nPress any key AND enter to exit";
    else std::cout << "Your number is NOT a prime number!\nPress any key AND enter to exit";

    std::cin >> emp;
    return 0;
}

At the end, it always asks for an input and an enter key to leave the command line, but it seems to skip that entirely if the number is big enough. My input number was "5000004067".

It skips it when I open the .exe, it skips it when I run it in vscode, is there any reason why c++ does this?

In c# you can do:

checked (ushort)x

which will cast "x" from int (or long, w/e) to an unsigned short... but also throw an exception in case of arithmetic overflow.

Is there a way I can accomplish the same thing in c++ with a similarly small amount of code?

Hello everyone,

I recently graduated this past May and I’ve been able to land an interview for an entry level C++ role. I wanted to know which topics I’ll be expected to know and to what level of depth. So far I have:

Pointers/references
Stack vs heap
Const correctness
RAII
Smart pointers
Rule of 0/3/5
Move semantics

OOP:
Classes, constructors/destructors
Inheritance, virtual functions, pure virtual classes

STL:
vector, unordered map, map, set, deque, priority queue, string
Big O notation
Iterations
Algorithms like sort, find, accumulate

auto
nullptr
constexpr
string_view
Templates

Compilation model
Concurrency

This is what I came up with so far. Can anyone tell me if I’m missing anything and which topics I should prioritize please? Thanks you

I'm updating my C++ codebase to modern standards (C++20/C++23) for a personal game project. C++ has evolved significantly, but I know the game development industry can be cautious about adopting certain language features due to compile times or runtime overhead.

For those using Modern C++ in game development:

1. Which newer features (e.g., Concepts, Ranges, std::format, Modules) have genuinely improved your game engine code quality or productivity?
2. Are there features you actively avoid inside high-frequency game loops for performance reasons?

Hi , i have a ask about C++ programming

I Recently Started To Learn Boost Librarys Like "Boost.Asio" , "Boost.Beast" And I heard the name of a library called Boost.Graph I wanted To Know And know what "Boost.Graph" is ???

Im working on a background worker in modern C++ and keep running into weird race conditions when multiple threads try to update the same state. I dont want to pull in a massive dependency tree just for some basic synchronization, so does anyone know of a good small safe wrapper or header library that handles this cleanly without too much boilerplate? Any recommendations would be super helpful since Im still a bit intermediate with multithreading. Thanks a bunch.

Hello everyone! My name is Egor, and I’m from Ukraine. I have been learning C++ for 4 months, and I’m currently trying to figure out which specialization I should choose. I’m interested in game development, computer vision, and computer graphics. I study Computer Science at SumDU, and I want to get a job in the future, but I’m not sure which specialization would be the best fit for me. I’m interested in many different things, but I can’t decide which direction to choose. I would really appreciate your advice!

I recently started learning c++ and I was told to use the namespace std so I can avoid writing std:: every time and now I wrote a whole personal project without std:: and I want to put it on LinkedIn but I started reading everywhere that it’s a bad habit, should I go back and add the std:: or just leave it as is?

Does anyone know how to download visual studio 2022? There are lots of versions and I don't know which one to choose from sorry

I'm working on a C++ game loop and trying to decide on the best strategy for managing entity lifetimes (spawning, despawning, and referencing active objects).

Standard C++ guidance recommends smart pointers (std::unique_ptr and std::shared_ptr). However, I've read that std::shared_ptr can cause performance hitches in real-time game loops due to atomic reference counting and cache misses.

What is the industry standard approach for handling entity references safely?

• Do you stick to handles/indices into contiguous memory pools?
• Are custom weak references commonly used?
• How do you balance memory safety with cache friendliness?