[net.micro.68k] bit addressing and floating point formats

shannon@sun.uucp (Bill Shannon) (09/04/84)

dmmartindale@watcgl.UUCP says:
	Thus you can use the "feature" of passing the address of a double where
	the address of its float portion is needed without having to add an offset.

It should be made clear that this is EXTREMELY non-portable.  It depends
on something which is not true on e.g. the Sun using IEEE floating point
format:

	The bit representation of a float is the same as the bit
	representation of a double except that it has fewer bits
	in the mantissa, and that the address of a double will
	point to a float with the "same" value.

On many machines, such as the Sun, this is NOT TRUE.  We have been
bitten quite a few times by code that passes the address of a float
to a routine expecting a pointer to a double.

					Bill Shannon
					Sun Microsystems, Inc.