On 7/8/21 10:52 AM, b. via gnumeric-list wrote: > is there anyone reading here who can help me to make the following snippet > fit > into gnumeric? i'm not a programmer, i've put it together and tinkered with > it a > bit, in LO Calc it gives me the exponent of an IEEE 754 'double' value as an > integer, in gnumeric error messages from the compiler. > double fVal1 = 0.0; > ... > fVal1 = GetDouble(); > ... > auto pValParts1 = reinterpret_cast < const sal_math_Double * > (&fVal1); > int nbinExp1 = pValParts1->inf_parts.exponent - 1023; > the alternatives 'log2(x)' or 'int(log2(x))' produce some - few - errors, > just > below range borders, increasing with the magnitude of x as the log2 curve > flattens.
I assume you are trying to emulate the C function frexp(). Here is a spreadsheet that does that. It's pretty straightforward: https://www.av8n.com/hack/frexp.gnumeric That includes about 15 test cases. The acid test is verifying that: a) The mantissa is in range, and b) The original input can be reconstructed exactly, using the computed exponent and mantissa. I "think" the calculation can be simplified by using C4 instead of E4, and getting rid of column E ... but I don't have a proof of this. _______________________________________________ gnumeric-list mailing list gnumeric-list@gnome.org https://mail.gnome.org/mailman/listinfo/gnumeric-list
