Emulation macros and pattern matching on D

[Dennis Ritchie via Digitalmars-d-learn]

On Friday, 5 June 2015 at 14:23:15 UTC, Steven Schveighoffer 
wrote:
> On 6/5/15 10:15 AM, Dennis Ritchie wrote:
>>
>> Thanks. It looks really simple, but I still do not understand 
>> the
>> concept of using mixins in full.
>>
>> I do not understand why in this line:
>> return `writefln("mode ` ~ mode ~ `: %s", ` ~ value ~ `);`;
>>
>> use the following syntax:
>> ~ mode ~ , ~ value ~
>
> Because what foo is constructing is a string that makes sense 
> in the *caller*, not inside foo. What those statements do is 
> concat the *value* of mode (i.e. "Y" or "X") and the *value* of 
> value (i.e. "3" or "2") to the string.
>
> It's equivalent to rust using the ${e} to do variable 
> substitution.

Thank you. Now everything is clear. Syntax `${e}` in Rust simpler 
than D ` ~ substitute the value ~ ` :)