char[][] join ==> string

[Simen kjaeraas]

On Thu, 07 Apr 2011 02:13:16 +0200, bearophile <bearophileHUGS at lycos.com>  
wrote:

> Given an array of strings std.string.join() returns a single string:
>
> import std.string;
> void main() {
>     string[] a1 = ["hello", "red"];
>     string j1 = join(a1, " "); // OK
> }
>
>
> But in a program I need an array of mutable arrays of chars. If I join  
> the arrays I get a mutable array of chars. But I need a string:
>
> import std.string;
> void main() {
>     char[][] a2 = ["hello".dup, "red".dup];
>     string j2 = join(a2, " "); // error
> }
>
> Error: cannot implicitly convert expression (join(a," ")) of type char[]  
> to string
>
> .idup avoids the error:
>
> string j3 = join(a2, " ").idup; // OK
>
> Given the low efficiency of the D GC it's better to reduce memory  
> allocations as much as possible.
> Here join() creates a brand new array, so idup performs a useless copy.  
> To avoid this extra copy do I have to write another joinString()  
> function?
>
> Bye,
> bearophile

Isn't this a prime case for std.exception.assumeUnique?

-- 
Simen