• David Nadlinger (16/16) Feb 20 2013 In Phobos, there are quite a few unit tests (std.format,
• Andrej Mitrovic (16/19) Feb 20 2013 I don't know about the exponent problem, but w.r.t. floating point
• Don (11/35) Feb 22 2013 Another related issue is the format of %a. On Windows it prints

"David Nadlinger" <see klickverbot.at> writes:

In Phobos, there are quite a few unit tests (std.format, 
std.json, ...) which assume that the %e floating point format 
zero-pads the exponent to (at least) two digits.

However, the printf-family functions in the MSVC and MinGW 
runtimes pad the exponent to *three* digits. For example, 
1.223e+24 is printed as "1.223e+024".

By extension, this also applies to the std.format (and thus 
std.stdio) floating point code, which relies on snprintf.

What is the correct fix here? Adjusting those unit tests? Doing 
something crazy along the lines of "if (result[$-4] == 'e' && 
result[$-3] == '0') { /+ trim zero +/ }"? (How) Is this handled 
on DMD/Win64?

The best way would probably be to just implement floating point 
printing in D as well, to isolate our code from such C runtime 
implementation differences.

David

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 2/20/13, David Nadlinger <see klickverbot.at> wrote:
 In Phobos, there are quite a few unit tests (std.format,
 std.json, ...) which assume that the %e floating point format
 zero-pads the exponent to (at least) two digits.

I don't know about the exponent problem, but w.r.t. floating point
there was a recent bug fixed where this source file:

auto x = 1.0;

Would be converted to this header file:

auto x = 1;

These are then different types. So I've changed how floating-point is
written in DMD to always emit "1.0" rather than "1". This also
improved diagnostics.

But I wanted to always print at most two digits in this case (e.g.
1.00, 2.00, etc) but couldn't find a good way to do it with sprintf,
so currently for floating-point e.g. "1" it prints "1.00000" in
diagnostics and header files, which is excessive.

Anyway I would definitely like to see floating-point printing
synchronized across multiple compilers and also the D library, to be
consistent everywhere.

"Don" <don nospam.com> writes:

On Wednesday, 20 February 2013 at 22:34:15 UTC, Andrej Mitrovic 
wrote:
 On 2/20/13, David Nadlinger <see klickverbot.at> wrote:
 In Phobos, there are quite a few unit tests (std.format,
 std.json, ...) which assume that the %e floating point format
 zero-pads the exponent to (at least) two digits.

 I don't know about the exponent problem, but w.r.t. floating 
 point
 there was a recent bug fixed where this source file:

 auto x = 1.0;

 Would be converted to this header file:

 auto x = 1;

 These are then different types. So I've changed how 
 floating-point is
 written in DMD to always emit "1.0" rather than "1". This also
 improved diagnostics.%

 But I wanted to always print at most two digits in this case 
 (e.g.
 1.00, 2.00, etc) but couldn't find a good way to do it with 
 sprintf,
 so currently for floating-point e.g. "1" it prints "1.00000" in
 diagnostics and header files, which is excessive.

 Anyway I would definitely like to see floating-point printing
 synchronized across multiple compilers and also the D library, 
 to be
 consistent everywhere.


Another related issue is the format of %a. On Windows it prints
0x1.444p+99
but on Linux the same number is
0x0.A22p+99
That's much easier to deal with, because it's trivial to print 
the %A format.
Correctly-rounded %e, %f is much more difficult, unfortunately 
(you need some
simple bigint arithmetic).