What are the differences between libfmt and std::format?
c++, c++20, fmt
Solution
There are a bunch of things in libfmt that are not in C++20 format:
- `fmt::print()` to print directly to stdout.
- `fmt::memory_buffer` as basically a dynamically sized container that you could format into via `fmt::format_to(buf, ...)`.
- Support for formatting ranges and tuples, including `fmt::join()`.
- Support for named arguments like `fmt::print("Elapsed time: {s:.2f} seconds", "s"_a=1.23);`
- Compile-time format strings via `FMT_COMPILE`, although both `fmt::format` and C++20's `std::format` do compile-time format string parsing by default. `fmt::format` has an escape hook for this named `fmt::runtime`, `std::format` has no such hook.
C++23 update: `std::print` (P2093) and formatting ranges and tuples (P2286) are in C++23.
Problem
I am aware that the c++20 format proposal is a formalization of parts of libfmt, and that libfmt is a compliant implementation of that formalization. However, it's my understanding that libfmt provides additional functionality beyond that specified in the c++20 standard. What are the additional features? Additional, are the major compiler vendors simply including a subset of libfmt or reimplementing it?