• cc (17/17) Jan 30 2018 import std.container;
• Steven Schveighoffer (7/25) Jan 30 2018 sformat requires a builtin array, apparently. It doesn't work for other
• cc (6/6) Jan 30 2018 Still doesn't work without the cast it seems..
• Steven Schveighoffer (10/16) Jan 31 2018 I misunderstood what you were trying to do. I thought you were just
• Seb (24/40) Jan 30 2018 For everything else, you can use formattedWrite:

cc <cc nevernet.com> writes:

	import std.container;
	import std.format;
	Array!char str;
	str.length = 256;

	str.sformat!"%s:%s"("some", "string");
	// Error: template std.format.sformat cannot deduce function 
from argument types !("%s:%s")(Array!char, string, string), 
candidates are:
	//   std.format.sformat(alias fmt, Args...)(char[] buf, Args 
args) if (isSomeString!(typeof(fmt)))
	//   std.format.sformat(Char, Args...)(char[] buf, in Char[] 
fmt, Args args)

	auto rng = cast(char[]) str[];
	// Error: cannot cast expression `str.opSlice()` of type 
`RangeT!(Array!char)` to `char[]`


Additionally, would sformat cause GC allocations even when 
writing to a preallocated buffer?

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 1/30/18 12:53 PM, cc wrote:
      import std.container;
      import std.format;
      Array!char str;
      str.length = 256;
 
      str.sformat!"%s:%s"("some", "string");
      // Error: template std.format.sformat cannot deduce function from 
 argument types !("%s:%s")(Array!char, string, string), candidates are:
      //   std.format.sformat(alias fmt, Args...)(char[] buf, Args args) 
 if (isSomeString!(typeof(fmt)))
      //   std.format.sformat(Char, Args...)(char[] buf, in Char[] fmt, 
 Args args)

sformat requires a builtin array, apparently. It doesn't work for other 
types.

 
      auto rng = cast(char[]) str[];
      // Error: cannot cast expression `str.opSlice()` of type 
 `RangeT!(Array!char)` to `char[]`

why not just auto rng = str[]?

 Additionally, would sformat cause GC allocations even when writing to a 
 preallocated buffer?

Not directly. If sformat needs to call a function on what you are asking 
to format that would use the GC, then it would not be  nogc.

-Steve

cc <cc nevernet.com> writes:

Still doesn't work without the cast it seems..

	auto rng = str[];
	rng.sformat!"%s:%s"("some", "string");
	// Error: template std.format.sformat cannot deduce function 
from argument types !("%s:%s")(RangeT!(Array!char), string, 
string)

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 1/30/18 2:19 PM, cc wrote:
 Still doesn't work without the cast it seems..
 
      auto rng = str[];
      rng.sformat!"%s:%s"("some", "string");
      // Error: template std.format.sformat cannot deduce function from 
 argument types !("%s:%s")(RangeT!(Array!char), string, string)

I misunderstood what you were trying to do. I thought you were just 
trying to get a valid range, missed the requirement that the range works 
with sformat (obviously from the subject! sorry).

Indeed, there isn't a way to extract an actual char[] from Array (and 
this is intentional).

But as Seb says, you can use formattedWrite:

auto rng = str[];
rng.formattedWrite("%s:%s", "some", "string");

-Steve

Seb <seb wilzba.ch> writes:

On Tuesday, 30 January 2018 at 18:42:45 UTC, Steven Schveighoffer 
wrote:
 On 1/30/18 12:53 PM, cc wrote:
      import std.container;
      import std.format;
      Array!char str;
      str.length = 256;
 
      str.sformat!"%s:%s"("some", "string");
      // Error: template std.format.sformat cannot deduce 
 function from argument types !("%s:%s")(Array!char, string, 
 string), candidates are:
      //   std.format.sformat(alias fmt, Args...)(char[] buf, 
 Args args) if (isSomeString!(typeof(fmt)))
      //   std.format.sformat(Char, Args...)(char[] buf, in 
 Char[] fmt, Args args)

 sformat requires a builtin array, apparently. It doesn't work 
 for other types.

For everything else, you can use formattedWrite:


```
import std.array : appender;
auto writer = appender!string();
writer.formattedWrite!"%s is the ultimate %s."(42, "answer");
writeln(writer.data);
```

without any GC:

```
/+dub.sdl:
dependency "emsi_containers" version="~>0.6.0"
+/
import std.format, std.stdio;

void main()
{
     import containers;
     DynamicArray!char arr;
     arr.formattedWrite!"%s is the ultimate %s."(42, "answer");
     printf("%.*s\n", arr.length, arr.ptr);
}
```

https://run.dlang.io/is/Taem9j