Re: Emulation macros and pattern matching on D

[Dennis Ritchie via Digitalmars-d-learn]

On Friday, 5 June 2015 at 13:13:15 UTC, Steven Schveighoffer 
wrote:
string foo(string mode, string value)
{
   return `writefln("mode ` ~ mode ~ `: %s", ` ~ value ~ `);`;
}
void main()
{
   mixin(foo("Y", "3"));
   mixin(foo("X", "2"));
}

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 ~

For example, why here I can simply write:

void main() {
    int b = 5;
    mixin(`int a = b;`);
    assert(a == 5);
}

Why should not I write like this:

void main() {
    int b = 5;
    mixin(`"int a = " ` ~ b ~ ` ";"`);
    assert(a == 5);
}