Looks like the largest decimal number that can be represented then is 4.50359962737E+15, or 4503599627370000
Bob S > On Dec 10, 2015, at 10:46 , Peter TB Brett <peter.br...@livecode.com> wrote: > > On 2015-12-10 17:54, Geoff Canyon wrote: >> LiveCode works in 64 bit numbers, so why does >> put 10000000000 * 1000000000000000000000000000000 >> result in >> 10000000000000000303786028427003666890752 >> which is close to the right answer, instead of some 18 digit value? > > When numbers are too large to represent exactly, LiveCode automatically > shifts to using 64-bit IEEE floating point representation. Floating-point > numbers store a number in three pieces: > > 1) a sign bit > 2) an exponent (11 bits) > 3) a mantissa (52 bits) > > This is a bit like writing decimal scientific notation. The "true" value is > 1.<MANTISSA> * 2^<EXPONENT>, modified by the SIGN. > > This means that much much larger numbers than 2^64 can be represented in only > 64 bits, but at the cost of loss of accuracy (because the mantissa is only 53 > bits). As you've noticed, the result of your calculation is only *close to* > the right answer. It can accurately represent any number that only requires > 53 bits of precision. > > See also https://en.wikipedia.org/wiki/Double-precision_floating-point_format > > Peter > > -- > Dr Peter Brett <peter.br...@livecode.com> > LiveCode Open Source Team > > LiveCode on reddit! <https://reddit.com/r/livecode> > > _______________________________________________ > use-livecode mailing list > use-livecode@lists.runrev.com > Please visit this url to subscribe, unsubscribe and manage your subscription > preferences: > http://lists.runrev.com/mailman/listinfo/use-livecode _______________________________________________ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
