> Whereas exceptions (in the C++/Java style) are free when they don’t fire, but very expensive when they do -- hundreds or thousands of cycles to parse exceptio

> Whereas exceptions (in the C++/Java style) are free when they don’t fire, but very expensive when they do -- hundreds or thousands of cycles to parse exception tables and unwind the stack. This isn't the whole story. The unwind control flow edges inhibit optimizations and increase code size. This is part of why C++ added `noexcept`. On the implementation freedom side of things, I am inclined to agree. For example, C++ is considering reimplementing exceptions as return values under the hood: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0709r0.pdf http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p070... (Though also note that an Either/Maybe/etc-style syntax could also be implemented as unwinding if you wanted to...)