[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]

*Subject*: **RE: [office-formula] 48 bits?**

*From*:**"Dennis E. Hamilton" <dennis.hamilton@acm.org>***To*: <dwheeler@dwheeler.com>,<patrick@durusau.net>*Date*: Tue, 22 Dec 2009 16:07:07 -0800

1. I think that the note under BITAND should be deleted. It provides unnecessary rationale. We have no idea how a spreadsheet implementation might handle exact integer values, which are all that are required for the bit-wise logical functions. Implications of using an IEEE standard do not apply here. 2. Some things about how Numbers (better: *exact* Integers) are mapped to and from bit-wise values for these functions is called for, perhaps in subsection 5.6.1 on General information for Bit operation functions. - Dennis FURTHER THOUGHTS 1. To satisfy the BITAND requirement we should probably specify *exact* Integer parameters (since the INT(n)=n constraint isn't assured to filter out values that are too large to be exact Integer values [and I am amazed to see that INT is defined as floor, i.e., the largest integer not greater than n). 2. We only need to require that the implementation define a value kbits so that exact integer values 0 to 2^kbits-1 are supported and kbits >=48. 3. We then describe the logical operations as operating on the kbits-bit binary numeral that represents the value supplied as the parameter, with the high-order bit, b[kbits-1] defined as at the left and low-order bit, b[0] defined to be at the right (for understanding shift operations). 4. You probably need to know what kbits are in order to completely specify what left shifting does. (That is, whether a shift left of one produces (x*2) mod 2^kbits or whether shifts off the high end have implementation-dependent results). 4. There are other things needed to tighten or to explicitly make implementation dependent. But no appeal to IEEE specifications of any kind is necessary here. -----Original Message----- From: David A. Wheeler [mailto:dwheeler@dwheeler.com] http://lists.oasis-open.org/archives/office-formula/200912/msg00114.html Sent: Tuesday, December 22, 2009 07:02 To: patrick@durusau.net Cc: office-formula@lists.oasis-open.org Subject: Re: [office-formula] 48 bits? Patrick Durusau: http://lists.oasis-open.org/archives/office-formula/200912/msg00113.html > I can't speak to the "need" to handle exactly 53 bits but why create a > variation from IEEE 754's 64-bit representation for numbers? There's *no* variation. The text explains the implications of *using* the IEEE standard... we are NOT changing anything. Many implementations do not support an infinite number of bits :-). Therefore, it's useful to specify a range that *is* guaranteed to be supported. Most people use IEEE 64-bit or better (e.g., 80-bit), and thus have at least 53 bits for the mantissa. Thus, if you're using integers, 48 bits of significance is within a portable range. --- David A. Wheeler --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. Follow this link to all your TCs in OASIS at: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php

**References**:**48 bits?***From:*Patrick Durusau <patrick@durusau.net>

**Re: [office-formula] 48 bits?***From:*"David A. Wheeler" <dwheeler@dwheeler.com>

[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]