Cached property (translate Python -> D)

[Victor Porton]

I've successfully implemented it myself:

---
import std.stdio;

mixin template Cached(string name, string baseName = '_' ~ name) {
     mixin("private typeof(" ~ baseName ~ ") " ~ name ~ "Cache;");
     mixin("private bool " ~ name ~ "IsCached = false;");
     mixin("@property typeof(" ~ baseName ~ ") " ~ name ~ "() {\n" 
~
           "if (" ~ name ~ "IsCached" ~ ") return " ~ name ~ 
"Cache;\n" ~
           name ~ "IsCached = true;\n" ~
           "return " ~ name ~ "Cache = " ~ baseName ~ ";\n" ~
           '}');
}

struct C {
     @property int _f() { writeln("Got!"); return 2; }
     mixin Cached!"f";
}

void main(string[] args)
{
     C x;
     writeln(x.f);
     writeln(x.f);
}
---

I think, we should add this to the standard library. What do you 
think?