Interpolated strings

[Jonas Drewsen via Digitalmars-d]

On Wednesday, 19 April 2017 at 00:08:19 UTC, Walter Bright wrote:
> On 4/18/2017 2:56 PM, Jonathan Marler wrote:
>> Have you thought about supporting format specifiers as well?  
>> I looked at the C#
>> version and it looks like they can specify them using a colon 
>> like this:
>>
>>     $"{a} in hex is {a:x}"
>
> There are additional problems, such as:
>
>     $"{a} in %s {b}"
>
> and positional parameters:
>
>     $"{a} in {0}"
>
> Of course, the easiest solution is to just disallow that stuff.

What about supporting an optional prefix inside the {} like:

int year = 2017;
format($"The date is {%04d year}");

so if there is a % immediately following the { then the chars 
until next whitespace is format specifier. You can of course 
leave out the format specifier and it will default to %s.