[squeakdev] Float class comment
Eliot Miranda
eliot.miranda at gmail.com
Tue Nov 25 17:42:18 UTC 2014
Hi All,
who wrote the Float class comment? Two things,
 first the comment mentions "I" and thanks several people, but there is no
comment stamp to reveal the author. It would be lovely if the author could
"sign" this comment
 second, there seems to be a minor error (but I'm no expert), the comment
states
"It may help you to know that the basic format is...
sign 1 bit
exponent 11 bits with bias of 1023 (16r3FF) to produce an exponent
in the range 1023 .. +1024
 16r000:
significand = 0: Float zero
significand ~= 0: Denormalized number (exp = 1024, no hidden '1' bit)
 16r7FF:
significand = 0: Infinity
significand ~= 0: Not A Number (NaN) representation
mantissa 53 bits, but only 52 are stored (20 in the first word, 32 in the
second). This is because a normalized mantissa, by definition, has a 1 to
the right of its floating point, and IEEE754 omits this redundant bit to
gain an extra bit of precision instead. People talk about the mantissa
without its leading one as the FRACTION, and with its leading 1 as the
SIGNFICAND."
But if the significand has a leading zero then surely the section in the
middle should read
sign 1 bit
exponent 11 bits with bias of 1023 (16r3FF) to produce an exponent
in the range 1023 .. +1024
 16r000:
mantissa = 0: Float zero
mantissa ~= 0: Denormalized number (exp = 1024, no hidden '1' bit)
 16r7FF:
mantissa = 0: Infinity
mantissa ~= 0: Not A Number (NaN) representation
Right?

best,
Eliot
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