On 12/16/2015 06:04 PM, tcak wrote:
On Wednesday, 16 December 2015 at 15:44:45 UTC, Andrei Alexandrescu wrote:
This has been discussed in the past and at a point Walter was looking
into it.
Currently std.conv.to applied to double uses snprintf, which is
obviously non-CTFEable.
There's been recent work (also discussed here) on fast accurate
printing of floating point values, see library "double-conversion"
written in C++ and the associated paper
http://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf.
Implementing that in D would be awesome because there are many many
applications of CTFEing doubles converted to text.
Andrei
If the purpose is to make it CTFEable, then we need to make it work at
first. So, there
is no need to focus on fast accurate implementation. I will try to
implement it by
multiplication and modulus operations at compile time. But I am not sure
about how long the decimal part (I don't know what the part after point
is called) should be. Would it be acceptable if it becomes 100 digits in
string? What is the limit?
Conversion of string to double should yield the double that has the
lowest absolute error. If this is ambiguous, the current rounding mode
determines the result.
Conversion of double to string should yield a shortest possible string
that when converted to double according to the above procedure gives
back the original value.
