[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

*To*: bug-lispm at MIT-AI*Subject*: Floating point representation*From*: DEKLEER at PARC-MAXC2*Date*: Sat ,27 Sep 80 11:32:00 EDT

FROM-JOB:LISP-MACHINE SENT-BY: TO:"(BUG-LISPM) TEXT;-1 In system 36.6 Ether, with microcode 683, on Xerox Machine 1: I had to write some code to convert floating-point numbers to BCPL floating-point format so that I could output splines to PRESS files (if you have already done this I would like to look at your code). In the process I discovered some strangeness in the representation. It seems to me that the floating-point representation of all negative integers is off in the bottom bit, is there some reason for this? One would expect that the reader could do better. For example, -2e0 is represented as: (describe -2e0) -2.0 is a flonum. Excess-2000 exponent 2001, 32-bit mantissa 20000000000 (including sign) (The mantissa is less than one in the bottom bit position, result is multiplied by 2.) While a more accurate representation would be: Excess-2000 exponent 2002, 32-bit mantissa 27777777777 (including sign) (The mantissa is exactly 1/2, result is multiplied by 4.) -------

- Prev by Date:
**That was from DLW, not TK!** - Next by Date:
**[no subject]** - Previous by thread:
**That was from DLW, not TK!** - Next by thread:
**Floating point representation** - Index(es):