# HAL Floating Point Unit API

This unit supplies a portable API over different FPUs. It was initially designed
over Intel x87 [asm/x87], but aims to be generic.

## The float format

When we refer to the "float" format, we refer to the 32-bit binary IEEE 754
format, which has a precision of 24 and an exponent range of -126 to 127:

  b31    Sign
  b30:23 Exponent
  b22:0  Mantissa

This API aims to be able to conveniently push and pop such numbers to/from the
FPU and manipulate them in the outside world as any regular 32-bit value.

## This API is going to change

Right now, this API is of a higher level than intended. I just want to get
floats "going" as fast as possible. The goal is to have a more HAL-ish API with
dedicated float registers so that integration in [comp/c] and friends is easier.

With x87's stack system, it's going to be a bit wonkish, but I think it will
work.

But before I do that I want to support more CPUs, at least ARM, to have a better
idea of what the floating world is out there before I design this.

## API

hasfloats? ( -- f )
  Yields whether this machine can do floats.

n>f ( n -- float )
  Converts an integer into a float.

f>n ( float -- n )
  Converts a float into an integer, truncating its decimal part.

f+ f- f/ f* ( float float -- float )
  Basic arithmethics.

fscale10 ( float exp -- float )
  Multiply "float" by 10 to the power of "exp", which can be negative.