Question for Parisse about CAS floating point

[Joe Horn]

(04-10-2015 07:58 PM)jte Wrote:  

(04-07-2015 02:44 AM)Joe Horn Wrote:  That's merely what's shown in the display. The internal value in CAS is exactly:
15.343434343434267930206260643899440765380859375
Count the underlined digits.

My understanding of the CAS semantics for its is inexact numeric values is that they are not exactly equal to any rational or real number.

If by "inexact" you mean "floating-point reals", then you are not correct. In CAS, reals use 48 bits for the mantissa, and are therefore exactly equal to an exact integer divided by an exact power of 2, which is therefore representable as an exact terminating decimal number. For example, the value of approx(1519/99) is stored by CAS as 134962275764989/2^43, which can be written exactly as the terminating decimal number I gave above.