I added an issue tracker entry 14536 Float class comment https://pharo.fogbugz.com/f/cases/14536
On 25 Nov 2014, at 18:42, Eliot Miranda <eliot.miranda@gmail.com> wrote:
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 IEEE-754 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