String joining an array of structs or class instances implementing toString?

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On Thursday, 11 February 2016 at 12:53:20 UTC, Edwin van Leeuwen 
wrote:
> I'd do it like this:
>
> import std.algorithm : map;
> pars.map!((part) => part.toString) // Turn them to strings
>  .join(" ").writeln; // Join them.

Thanks! Does the map function iterate without constructing an 
extra list in-memory?