Install fmt if not already installed

git clone https://github.com/fmtlib/fmt.git
cd fmt
mkdir build && cd build
cmake ..
make -j$(nproc)
sudo make install

Then build

g++ -std=c++20 -Wall -Wextra -Wpedantic -Wconversion -Wsign-conversion \
    -Wshadow -Wold-style-cast -Wcast-qual -Wuseless-cast \
    -Wdouble-promotion -Wformat=2 -Wnull-dereference -Wduplicated-cond \
    test.cpp -lfmt -o test

Tested with GCC 16.1.0 on Ubuntu (x86_64), C++20 mode.

Can work.

Note: I genuinely didn't know std::format had already absorbed {fmt} in C++20 when I first wrote this.
However, std::print is not available until C++23, and I'm used to fmt::print.
That’s why this project still depends on the {fmt} library — old habits, and one missing function. 😅