• rumbu (10/10) Nov 09 2015 Let's say that I'm a library provider and I intend to offer a
• H. S. Teoh via Digitalmars-d-learn (11/24) Nov 09 2015 Do you need *custom* format specifiers? If all you need is to be able to
• rumbu (4/16) Nov 09 2015 I'm working to create a decimal data type library, therefore I
• Adam D. Ruppe (5/7) Nov 09 2015 I would pull request that to move it into its own independent

rumbu <rumbu rumbu.ro> writes:

Let's say that I'm a library provider and I intend to offer a 
completely new data type suitable for printing with format() or 
writef().

According to this tutorial 
(http://wiki.dlang.org/Defining_custom_print_format_specifiers), 
to achieve this, one must import at least std.format : FormatSpec.

The problem is that just importing FormatSpec will create exactly 
88 phobos dependencies.

Is there any way to provide formatting capabilities for a custom 
data type without importing the FormatSpec thing?

"H. S. Teoh via Digitalmars-d-learn" <digitalmars-d-learn puremagic.com> writes:

On Mon, Nov 09, 2015 at 03:09:26PM +0000, rumbu via Digitalmars-d-learn wrote:
 Let's say that I'm a library provider and I intend to offer a
 completely new data type suitable for printing with format() or
 writef().
 
 According to this tutorial
 (http://wiki.dlang.org/Defining_custom_print_format_specifiers), to
 achieve this, one must import at least std.format : FormatSpec.
 
 The problem is that just importing FormatSpec will create exactly 88
 phobos dependencies.
 
 Is there any way to provide formatting capabilities for a custom data
 type without importing the FormatSpec thing?

Do you need *custom* format specifiers? If all you need is to be able to
write: format("%s", myData), then the only thing you need to do is to
implement one of the toString methods recognized by format(), such as:

	void toString(scope void delegate(const(char)[]) dg) {
		...
	}

and format() should be able to just pick it up.


T

-- 
You have to expect the unexpected. -- RL

rumbu <rumbu rumbu.ro> writes:

On Monday, 9 November 2015 at 16:11:23 UTC, H. S. Teoh wrote:
 On Mon, Nov 09, 2015 at 03:09:26PM +0000, rumbu via 
 Digitalmars-d-learn wrote:
 [...]

 Do you need *custom* format specifiers? If all you need is to 
 be able to write: format("%s", myData), then the only thing you 
 need to do is to implement one of the toString methods 
 recognized by format(), such as:

 	void toString(scope void delegate(const(char)[]) dg) {
 		...
 	}

 and format() should be able to just pick it up.


 T

I'm working to create a decimal data type library, therefore I 
need at least %f %e %a and %g, including other data like width, 
precision and so on.

Adam D. Ruppe <destructionator gmail.com> writes:

On Monday, 9 November 2015 at 15:09:28 UTC, rumbu wrote:
 The problem is that just importing FormatSpec will create 
 exactly 88 phobos dependencies.

I would pull request that to move it into its own independent 
module and then make std.format import that. I know that's not an 
immediate solution but it should go through by the next release; 
i doubt such a PR would be controversial.