RPNPRGM: New Windows console application emulating HP calculators

01292021, 01:50 PM
Post: #12




RE: RPNPRGM: New Windows console application emulating HP calculators
(01282021 04:16 PM)Aacini Wrote: [*] The management of 80bits floating point numbers, that allows to enter and display numbers with 19 decimal digits and an exponent of ten above 4000. Hi, Aacini It may be better if display numbers extended to 21. Minimum digits d that will roundtrip b bits: d = ceil(b*(log(2)/log(10))) + 1 53 bits → d = ceil(15.9546) + 1 = 17 // double precision 64 bits → d = ceil(19.2659) + 1 = 21 // extended precision Better yet, have an option to enter/display hexfloat.  Is this a RPN.exe bug ? I use 1e16 + 2.9999 to test for rounding behavior (note: 1e16 slightly bigger than 2^53) With double precision, 2.9999 get roundeddown, sum = 1e16 + 2 With extended precision, 2.9999 get roundedup, sum = 1e16 + 3 If extended precision then roundback to double, sum = 1e16 + 4 But, this is not what observed: > RPN.exe 1e16 2.9999 + eng:19 ; note: eng:19 is 19 digits, not 20 10.00000000000000300E+0015 > RPN.exe 1e16 2.9999 + fix:0 ; should hit with doublerounding errors, returning 1e16+4 10000000000000002 For some strange reason, the flip occurs much higher: >RPN.exe 1e16 3.00634 + fix:0 10000000000000002 >RPN.exe 1e16 3.00635 + fix:0 10000000000000004  A minor issue, numbers starting with decimal point are not recognized: RPN: .123 Invalid operator: . RPN: .123 Wrong number: . 

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