ieee.float_pkg is the floating-point package of the VHDL standard, IEEE Std 1076-2008 and 1076-2019. The source is the IEEE's own: ieee/float_generic_pkg-body.vhdl on the release branch of opensource.ieee.org/vasg/Packages, 5,712 lines, $Revision: 1220 $. The working group's develop branch at gitlab.com/IEEE-P1076/Packages has the same bytes, and GHDL and NVC ship them unchanged. The runs here are in GHDL 7.0.0-dev and NVC 1.23.1, and where both ran the same vectors they wrote the same result file.
The package is set beside exact arithmetic. An operand is a sign and a fraction of two integers, the operation is done on the fractions, and the result is rounded once into the format in the rounding style the call names. exact.py is that reference.
