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digitalmars.D.bugs - [Issue 5687] New: std.string.format() error with "%a"

reply d-bugmail puremagic.com writes:
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           Summary: std.string.format() error with "%a"
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: bugzilla kyllingen.net



23:23:44 PST ---
Magnus Lie Hetland wrote in D.learn:

I just noticed that writefln("%a", 1.2) writes 0x1.3333333333333p+0, while
writeln(format("%a", 1.2)) (that is, with std.string.format) writes
0x9.9999999999998p-3 ... wouldn't it be nice to be consistent here? (The former
is what printf in gcc gives.)

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next sibling parent d-bugmail puremagic.com writes:
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00:27:42 PST ---
I've found the cause for this:  1.2 is a double, and should be formatted as
such, but it is converted to a real internally in std.format.doFormat().

I think the right way to go is to rewrite std.string.format() in terms of
std.format.formattedWrite() instead of std.format.doFormat().

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug yahoo.com.au





 I've found the cause for this:  1.2 is a double, and should be formatted as
 such, but it is converted to a real internally in std.format.doFormat().


I don't think that's the reason. On Windows, the %A format always begins with
0x1.  (except of course for 0, NaN, inf).
You will never, under any circumstances, see something beginning with 0x9.
Is it actually true that %A on Linux for doubles always begins with 0x1.  ?
If so, then it's a Linux %A bug for reals.

In fact, converting from double to real should NEVER change the %a result.



 I think the right way to go is to rewrite std.string.format() in terms of
 std.format.formattedWrite() instead of std.format.doFormat().


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On Windows:

import std.stdio;
import std.string;

void main()
{
    writefln("%a", 1.2);
    writeln(format("%a", 1.2));
}
-------
0x1.3333333333333p+0
0x1.3333333333333p+0
-------
This bug is Linux-only.

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01:57:22 PST ---


 Is it actually true that %A on Linux for doubles always begins with 0x1.  ?


Having tested with a large number of random doubles, that certainly seems to be
the case.


 If so, then it's a Linux %A bug for reals.


Wow, you'd think someone would have discovered this before.


 In fact, converting from double to real should NEVER change the %a result.


Thinking some more about it, that makes sense.

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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla digitalmars.com



11:55:36 PST ---
%a and %A formatting is done in Phobos using snprintf, which (sadly) produces
different results on Windows than Linux.

In order to properly fix this, we just need to write our own %a formatter.

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Stewart Gordon <smjg iname.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |smjg iname.com
         Resolution|                            |DUPLICATE



*** This issue has been marked as a duplicate of issue 4532 ***

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