Re: about float double
spir: Is there somewhere a (clear) doc about float/double internals? Some more particuliar questions: What is the internal bit layout? (mantissa, sign, exponent) There is the real type too (= 10 bytes). Bye, bearophile
Re: about float double
Is there somewhere a (clear) doc about float/double internals? Some more particuliar questions: What is the internal bit layout? (mantissa, sign, exponent) Can I assume the integral range is [-2^(m-1) .. 2^�m-1)-1], where m is the number of mantissa bits? What are the values used to represent thingies like NaNs, inf, error? (Or are there not represented as values?) How would you get a float's integral and fractional parts without performing arithmetic? (I think at bit ops, indeed) Wikipedia is very informative and the phobos math implementation is a very good source for the bit ops stuff http://www.dsource.org/projects/phobos/browser/trunk/phobos/std/math.d
about float double
Hello, Is there somewhere a (clear) doc about float/double internals? Some more particuliar questions: What is the internal bit layout? (mantissa, sign, exponent) Can I assume the integral range is [-2^(m-1) .. 2^⁽m-1)-1], where m is the number of mantissa bits? What are the values used to represent thingies like NaNs, inf, error? (Or are there not represented as values?) How would you get a float's integral and fractional parts without performing arithmetic? (I think at bit ops, indeed) Denis _ vita es estrany spir.wikidot.com
Re: about float double
spir wrote:
Is there somewhere a (clear) doc about float/double internals?
A very good read is:
http://digitalmars.com/d/2.0/d-floating-point.html
Some more particuliar questions:
What is the internal bit layout? (mantissa, sign, exponent)
IEEE floating point format. This page has links to different
representations:
http://en.wikipedia.org/wiki/Ieee_floating_point
Specifically:
http://en.wikipedia.org/wiki/Single_precision_floating-point_format
http://en.wikipedia.org/wiki/Double_precision_floating-point_format
What are the values used to represent thingies like NaNs, inf, error?
(Or are there not represented as values?)
They are available on the documents above.
How would you get a float's integral and fractional parts without
performing arithmetic? (I think at bit ops, indeed)
Here is a function with endianness issues that I had used with
different types:
import std.stdio;
void display_bytes(T)(ref T variable)
{
const ubyte * begin = cast(ubyte*)variable;
writefln(type : %s, T.stringof);
writefln(value : %s, variable);
writefln(address : %s, begin);
writef( representation: );
foreach (p; begin .. begin + T.sizeof) {
writef(%02x , *p);
}
writeln();
writeln();
}
void main()
{
auto d_nan = double.nan;
auto d_inf = double.infinity;
display_bytes(d_nan);
display_bytes(d_inf);
}
Ali
