Two-bit oop tags (was: [SqF]Report of VI4 Project for Feb '02)
Jecel Assumpcao Jr
jecel at merlintec.com
Sun Feb 3 08:03:15 UTC 2002
Self uses two bits for its tags: oops, small integers, floats and
headers.
30 bit floating point numbers are probably not a good idea. They make
people have to deal with rounding errors in nearly all applications
while larger representations will let them get by in blissful ignorance
most of the time.
The header tags speed up memory scanning operations. Instead of
for each object
for each word in object
is it what we are looking for?
you have
for each word in memory
is it what we are looking for?
back up to previous header
Personally, I would keep the current 1 bit scheme. But if you think
faster scanning is worth it, then Tim's 1, 00 and 10 encoding would be
nice. They could be small int, oop and header respectively.
-- Jecel
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