I have files a phobos bug report.

http://d.puremagic.com/issues/show_bug.cgi?id=8326

Regards
- Puneet

std.string.format uses std.format.doFormat, and it is based on RTTI.
On the other hand, writeln/writefln uses std.format.formattedWrite and
formatValue, they are based on Compile Time Reflection.
So the results are different.

In 2.060head, std.string.xformat is added, and it works as like writefln. https://github.com/D-Programming-Language/phobos/blob/master/std/string.d#L2611

Bye.

Kenji Hara

2012/7/1 d coder <dlang.coder@gmail.com>:
> Greetings
>
> std.string.format throws runtime exception for BigInt and for BitArray types even though writefln works fine. The run-time error says std.format.FormatException@std/format.d(4744): Can't convert std.bigint.BigInt to string: "string toString()" not defined
>
> Here is a small test case.
>
> Regards
> - Puneet
>
> void main()
> {
>   import std.stdio;
>   import std.string;
>   import std.bigint;
>   import std.bitmanip;
>
>   BigInt aa = 100;
>
>   BitArray bb;
>   bb.init([true, false]);
>
>   writefln("%x", aa);
>   writefln("%x", bb);
>   writeln(format("%x", aa));
>   writeln(format("%x", bb));
> }
>

Thanks Kenji, I will use xformat. BTW, why is it named "x"format? Would not "s"format be a better name? Where "s" could stand for string.

Also I feel, std.string.format should work for BitArray and BigInt too. Both these types are defined as part of phobos.

Regards
- Puneet

2012/7/1 d coder <dlang.coder@gmail.com>:
> Thanks Kenji, I will use xformat. BTW, why is it named "x"format? Would not "s"format be a better name? Where "s" could stand for string.

eXtended format.

> Also I feel, std.string.format should work for BitArray and BigInt too. Both these types are defined as part of phobos.

We couldn't replace the implementation of std.string.format directly.

See the discussion: https://github.com/D-Programming-Language/phobos/pull/231

But, in the future, xformat would be renamed to format.

Kenji Hara

Thanks Kenji.