Re: Parsing timestamps?

dxf <dxforth@gmail.com> writes:

I suspect IEEE simply standardized what had become common practice among
implementers.

Not at all.  There was no common practice at the time.

While there was some sentiment to standardize the VAX FP stuff, and as
far as number formats are concerned, they almost did (IEEE binary32
uses the same format as the VAX F, IEEE binary64 uses the same format
as VAX G, and IEEE binary128 uses the same format as VAX H), if we
ignore the perverse byte order of the VAX formats.  However, IEEE FP
uses a different bias for the exponent, requires implementing denormal
numbers, infinities and NaNs.

So actually none of the hardware manufacturers implemented IEEE FP at
the time, not DEC, not IBM, and not Cray.  And yet, industry accepted
IEEE FP and within a few years all new architectures supported IEEE
FP, and new models of existing hardware usually also implemented IEEE
FP.

By using 80 bits /internally/ Intel went a long way to
achieving IEEE's spec for double precision.

The 8087 did not just use 80 bits internally, it exposed them to
programmers.  When Intel released the 8087, IEEE 754 was not finished.
But Kahan was both active in the standardization community and in the
8087 development, so you can find his ideas in both.  His and Intel's
idea was that the 8087 would be IEEE standard-conforming, but given
that the standard came out later, that was not quite the case.

E.g. doing something as simple as changing
sign of an fp number is a pain when NANs are factored in.

I don't see that.  When you change the sign of a NaN, it's still a
NaN.

- anton
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