Hexadecimal Floating Point? Why? How?

Why in the world would anyone want to write a floating-point number in
hexadecimal? Is the '.' in such a number still a "decimal point", or
is it a "hexadecimal point"? What would that even mean??

As it turns out, hex floating point literals are, if not strictly
necessary, still pretty sweet when you get serious about numeric
computation. The WebGPU Shading Language (WGSL), a cross-platform
language for writing code to run on GPUs, supports hex floats, and as
one of the maintainers of the Naga shader translator crate, Jim Blandy
has to support them.

Tonight Jim will narrate the bit-fiddling derring-do and uncalled-for
consistency and completeness he indulged in while reimplementing
Naga's hexadecimal floating-point literal parsing code. It'll be geeky
and obscure. But the truth is that floating-point arithmetic is
actually much nicer and more predictable than people think, and
getting that nasty decimal conversion out of the way makes that easier
to see.