C++

Bjarne Stroustrup started C++ at Bell Labs as “C with Classes”, and the first commercial release came in 1985. It keeps C’s speed and its direct access to memory and adds classes, templates, and a large standard library of containers and algorithms. Games, browsers, databases, and trading systems are written in it, and so are the engines under data science libraries such as TensorFlow, PyTorch, and XGBoost, none of which is installed here.

The implementations use C++23, compiled with g++ with every warning an error. The standard library brings std::vector, std::map, std::sort, and std::println, but no statistics and no matrices, so the methods are written out.

Quirks

• std::accumulate adds in the type of its starting value: from 0 it sums 28.6, 43.8, and 11.5 to 82, from 0.0 to 83.9, and the compiler doesn’t warn.
• Sizes are unsigned. On a vector of 3, v.size() - 4 is 18446744073709551615, not −1.
• Parentheses and braces build different vectors: std::vector<int> a(3, 1) is three 1s, but b{3, 1} is the two numbers 3 and 1.
• v[5] past the end is undefined behavior, with no check; v.at(5) checks and throws std::out_of_range.
• Template errors are long. Passing a whole vector to std::println, which GCC 14 can’t format yet, produces 131 lines of errors.

git clone https://github.com/qnixon/dswithx.git
cd dswithx
python3 harness/run_tests.py --language cpp