C++ - Reddit

Request for review: C++ arbitrary-precision library (base 1e9, decimals, signs, relational operators) Hi everyone I've been working on a C++ Long Numeric Arithmetic Library for arbitrary-precision numbers. It started as a small factorial project and now supports extremely large numbers efficiently. I'd love constructive criticism from experienced C++ developers. Features: - Arbitrary-precision integers with base 1e9 storage - Decimal + sign support - Full set of relational operators (<, >, ==) - Factorial up to 10,000!, faster than Java BigInt sequential factorial calculation // Demonstrates factorial, decimal support, and relational operators Example usage:

Number fact = factorial(10000); 
// 10,000! computed faster than Java BigInt

string data = numb_to_str(fact).substr(0,10); // Show first 10 digits
cout << data << endl;

Number a, b;
str_to_numb("123451.23499236325652399991", a);

str_to_numb("67832678263123451.23499236325652399990", b);

if (a < b) {
    cout << "a is smaller than b" << endl; // Relational operator works
}

Benchmarks: Graph included showing computation time for factorials up to 10,000 versus Java BigInt sequential factorial. Benchmarking link repo - > Long Numeric Arithmetic I'd appreciate constructive criticism on: - C++ code structure and idiomatic practices - Performance optimizations - API usability and naturalness of relational operators - Any tips for memory efficiency and decimal/sign handling Thanks in advance for taking the time to review your feedback will be really helpful ! https://redd.it/1n6cghn @r_cpp

Could you recommend nay good materials for c++ 17 or upper? My knowledge of capital stuck in c++ 11 or c++ 14 and I think I need a real quick updates. Could you recommend some? https://redd.it/1n6c913 @r_cpp

Is there any good tiny xml equivalents for json? I've been working on a project that'll need me to store data. I was thinking about using json for this, but I'm having a hard time finding a library to parse json as usable as tiny xml. Are there any tiny xml-esque libraries that are for json? Anything helps. https://redd.it/1n6bjpm @r_cpp

The case against Almost Always `auto` (AAA) https://gist.github.com/eisenwave/5cca27867828743bf50ad95d526f5a6e https://redd.it/1n69bbm @r_cpp

How to understand any piece of code Hi guys. One of the most important skills a programmer needs is to be able to understand any piece of code. So, my question is, how do you do that? Do you have any tips or advice? https://redd.it/1n5xrxr @r_cpp

C++ Builder 2006 It's interesting to know how many others like me are out there. I use it for creating mathematical models of orbital motion (no small feat, by the way не хухры мухры), as well as for software that simulates the operation of certain systems... I use...... C++ Builder 2006 (10.157) and I consider this IDE excellent for such tasks, but I've never seen anyone else who also works with it. I wonder if I might find people who also write software on it. It has a few quirks, like the fact that it can randomly (by freezing for exactly 0.1 seconds) delete an entire page of a file, and many other various quirks, but it's just so incredibly simple to write software in it. I know about Embarcadero C++ Builder 2010, but it doesn't have the code completion hints (or whatever they are called) that work perfectly in the 2006 version. https://redd.it/1n5r39n @r_cpp

Declaration before use There is a rule in C++ that an entity must be declared (and sometime defined) before it is used. Most of the time, not enforcing the rule lead to compilation errors. In a few cases, compilation is ok and leads to bugs in all the cases I have seen. This forces me to play around rather badly with code organization, include files that mess up, and sometime even forces me to write my code in a way that I hate. I may have to use a naming convention instead of an adequate scope, e.g. I can't declare a struct within a struct where it is logical and I have to declare it at top level with a naming convention. When code is templated, it is even worse. Rules are so complex that clang and gcc don't even agree on what is compilable. etc. etc. On the other hand, I see no benefit. And curiously, I never see this rule challenged. Why is it so ? Why isn't it simply suppressed ? It would simplify life, and hardly break older code. https://redd.it/1n5m6hf @r_cpp

Maki, a C++17 Finite-State Machine Library https://github.com/fgoujeon/maki https://redd.it/1n5lxgu @r_cpp

Managing transitive dependencies - msbuild + vcpkg Let's say we have a static library in Visual Studio that uses vcpkg to pull in dependencies. We also have an executable that pulls in this library using a project reference. Is there some sort of configuration that will pull in all the runtime dependencies to the executable build directory? I can't figure it out. Assume we are using MSBuild/vcxproj files. https://redd.it/1n5jlia @r_cpp

C++ Show and Tell - September 2025 Use this thread to share anything you've written in C++. This includes: * a tool you've written * a game you've been working on * your first non-trivial C++ program The rules of this thread are very straight forward: * The project must involve C++ in some way. * It must be something you (alone or with others) have done. * Please share a link, if applicable. * Please post images, if applicable. If you're working on a C++ library, you can also share new releases or major updates in a dedicated post as before. The line we're drawing is between "written in C++" and "useful for C++ programmers specifically". If you're writing a C++ library or tool for C++ developers, that's something C++ programmers can use and is on-topic for a main submission. It's different if you're just using C++ to implement a generic program that isn't specifically about C++: you're free to share it here, but it wouldn't quite fit as a standalone post. Last month's thread: https://www.reddit.com/r/cpp/comments/1mgt2gy/c_show_and_tell_august_2025/ https://redd.it/1n5jber @r_cpp

Structured bindings in C++17, 8 years later https://www.cppstories.com/2025/structured-bindings-cpp26-updates/ https://redd.it/1n5hn44 @r_cpp

Debugging unfamiliar codebase for lazy coder I want to fix a bug in a 50K line C++ codebase but am too tired these days to work through the debugger myself. (I basically retired from coding). Especially as the bug might reside in code from the '90s. What's the easiest debugger or way to find and fix this? Maybe some AI or something off upwork? https://redd.it/1n5dyyd @r_cpp

We need to seriously think about what to do with C++ modules https://nibblestew.blogspot.com/2025/08/we-need-to-seriously-think-about-what.html https://redd.it/1n53mpl @r_cpp

Challenges and Solutions - Mostafa Mahmoud Ali - https://youtu.be/O-O\_c6Ymz8w Unveiling C++ Type Erasure - From std::function to std::any - Sarthak Sehgal - [https://www.youtube.com/kI2NRnsC5GA](https://www.youtube.com/watch?v=kI2NRnsC5GA) 2025-08-11 - 2025-08-17 Back When ChatGPT Was Young and Stupid - Andrei Zissu - https://youtu.be/xAGwdm-Ml\_A ArkScript - A Small, Fast, Functional & Scripting Language for C++ Projects - Alternative to Python! - Alexandre Plateau - [https://youtu.be/ZqAMzdAzdbg](https://youtu.be/ZqAMzdAzdbg) Unlock the Power of Asynchronous C++ Programming with Tinycoro - Tamas Kovacs - https://www.youtube.com/TVrrhVvjBaE 2025-08-04 - 2025-08-10 C++ Coroutines With tinycoro - Tamás Kovács - [https://youtu.be/o5Zh-956rrs](https://youtu.be/o5Zh-956rrs) Info Dump - Integer log2, De Bruijn Sequences, and BSR and LZCNT of x86 - Pavel Novikov - https://youtu.be/SsLdxUDDaDk Kicking off PPP book on macOS - Paulo Chiliguano - [https://www.youtube.com/xnA98b2Mng4](https://www.youtube.com/watch?v=xnA98b2Mng4) 2025-07-28 - 2025-08-03 Tips and Tricks for Improving C++ Legacy Codebases - Roth Michaels - C++Online 2025 - https://youtu.be/D8TVX1HGn6M Optimizing SPSC Lockfree Queue - Sarthak Sehgal - [https://youtu.be/Zg5wuEExY8M](https://youtu.be/Zg5wuEExY8M) So You Wanna Delve Into C++? - Honey Sukesan - https://youtu.be/cUbxzuu6yPQ https://redd.it/1n4y1rt @r_cpp

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New C++ Conference Videos Released This Month - August 2025 (Updated To Include Videos Released 2025-08-25 - 2025-08-31) C++Now 2025-08-25 - 2025-08-31 From SIMD Wrappers to SIMD Ranges - Denis Yaroshevskiy & Joel Falcou Part 1 - https://youtu.be/CRe20RdU\_5Q Part 2 - [https://youtu.be/20rl8xDaJrg](https://youtu.be/20rl8xDaJrg) C++ Memory Safety in WebKit - Geoffrey Garen - https://youtu.be/RLw13wLM5Ko Post-Modern Cmake - From 3.0 to 4.0 - Vito Gamberini - [https://youtu.be/K5Kg8TOTKjU](https://youtu.be/K5Kg8TOTKjU) 2025-08-18 - 2025-08-24 Extending std::execution - Implementing Custom Algorithms with Senders & Receivers - Robert Leahy - https://youtu.be/zcNip8ydpmM Safer C++ at Scale with Static Analysis - Yitzhak Mandelbaum - [https://youtu.be/3zQ4zw4GNV0](https://youtu.be/3zQ4zw4GNV0) Harnessing constexpr - A Path to Safer C++ - Mikhail Svetkin - https://youtu.be/THkLvIVg7Q8 2025-08-11 - 2025-08-17 Beyond Sequential Consistency - Leveraging Atomics for Fun and Profit - Christopher Fretz - [https://youtu.be/qNs0\_kKpcIA](https://youtu.be/qNs0_kKpcIA) Welcome to v1.0 of the meta::[[verse\]\]! - Inbal Levi - https://youtu.be/BKIuIh3Jo\_s Missing (and Future?) C++ Range Concepts - Jonathan Müller - [https://youtu.be/RemzByMHWjI](https://youtu.be/RemzByMHWjI) 2025-08-04 - 2025-08-10 How to Avoid Headaches with Simple CMake - Bret Brown - https://youtu.be/xNHKTdnn4fY import CMake; // Mastering C++ Modules - Marching Towards Standard C++ Dependency Management - Bill Hoffman - [https://youtu.be/uiZeCK1gWFc](https://youtu.be/uiZeCK1gWFc) Undefined Behavior From the Compiler’s Perspective - A Deep Dive Into What Makes UBs So Dangerous, and Why People Rightfully Continue To Use Them Anyways - Shachar Shemesh - https://youtu.be/HHgyH3WNTok C++ On Sea 2025-08-25 - 2025-08-31 An Introduction to Reinforcement Learning - Snake Your Way out of a Paper Bag - Frances Buontempo - [https://youtu.be/jeoJZ8XGJCg](https://youtu.be/jeoJZ8XGJCg) CMake for the Impatient - Steve Love - https://youtu.be/t6iV5\_plo20 Software Engineering Completeness - Knowing When You Are Done and Why It Matters - Peter Muldoon - [https://youtu.be/NYw\_QeZYSzQ](https://youtu.be/NYw_QeZYSzQ) 2025-08-18 - 2025-08-24 Building Robust Inter-Process Queues in C++ - Jody Hagins - https://youtu.be/nX5CXx1gdEg The Pattern Matching We Already Have - Braden Ganetsky - [https://youtu.be/2tkkAFCWGbM](https://youtu.be/2tkkAFCWGbM) Understanding C++ Value Categories: lvalue, rvalue, xvalue, std::move, std::forward & Best Practices - Sandeep Mantrala - https://youtu.be/d5h9xpC9m8I 2025-08-11 - 2025-08-17 Three Cool Things in C++26: Safety, Reflection & std::execution - Herb Sutter - [https://youtu.be/kKbT0Vg3ISw](https://youtu.be/kKbT0Vg3ISw) Namespaces 101 - Sandor DARGO - https://youtu.be/uh9RWX-SXvc ACCU Conference 2025-08-25 - 2025-08-31 Keynote: Teaching an Old Dog New Tricks - Matt Godbolt - [https://youtu.be/jlt\_fScVl50](https://youtu.be/jlt_fScVl50) How To Manage Asynchronous Control Flow With C++ Coroutines - Andreas Weis - https://youtu.be/lKUVuaUbRDk How Old Am I in Seconds and Other Insights From the C++ chrono Library - Nicolai M. Josuttis - [https://youtu.be/HTiNq95S3TM](https://youtu.be/HTiNq95S3TM) 2025-08-18 - 2025-08-24 C++ ♥ Python - Accelerating Python With C++ - Alex Dathskovsky - https://youtu.be/wKZio\_KAMQ0 Challenges and Benefits of Upgrading Sea of Thieves From C++14 to C++20 - Keith Stockdale - [https://youtu.be/Nm9-xKsZoNI](https://youtu.be/Nm9-xKsZoNI) Continuous Integration (CI) for Large Scale Package-Based C, C++ Projects With Conan2 - Diego

switch constexpr C++17 introduced if constexpr statements which are very useful in some situations. Why didn't it introduce switch constexpr statements at the same time, which seems to be a natural and intuitive counterpart (and sometimes more elegant/readable than a series of else if) ? https://redd.it/1n4wrff @r_cpp

Resources for bit manipulation? Hey! I’m learning bit manipulation techniques for a project I’m working on, so I’m curious if any of you have learning resources or best practices you would recommend. https://redd.it/1n4f7in @r_cpp

With P2786R13 (Trivial Relocatability) and private destructors, we can implement "Higher RAII" in C++26 This is a though I just had 30 minutes ago. As a big fan of Vale's "higher RAII" (IMO a bad name, it's more or less referring linear types), I hoped that one day C++ would get destructive moves, which was the missing part to achieve higher RAII. With P2786R13 and a use-after-relocation warning as error this pretty much gets us here. https://redd.it/1n4fm9r @r_cpp

Post-Modern Cmake - From 3.0 to 4.0 - Vito Gamberini - C++Now 2025 https://www.youtube.com/watch?v=K5Kg8TOTKjU https://redd.it/1n4a8d4 @r_cpp