I guess this is a feature request.

Say you've got:
char[] a, b, c, d;

I think that this:
a = b ~ c ~ d;

..should cancatenate in one step, kinda like this:
a.length = b.length + c.length + d.length;
a[0                   .. b.length] = b;
a[b.length            .. c.length] = c;
a[b.length + c.length .. d.length] = d;

..instead of working like this:
a = (b ~ c) ~ d;

It would be faster because it involves less copying and allocation, right?

Does the D language spec allow concatenation to be implemented that way? or does it require something like a strict left to right order of operations, one concatenation operator at a time? How do dmd and gdc do it?

-Sterling

On Tue, 19 Apr 2005 23:32:44 +0000 (UTC), Sterling Christensen wrote:

> I guess this is a feature request.
> 
> Say you've got:
> char[] a, b, c, d;
> 
> I think that this:
> a = b ~ c ~ d;
> 
> ..should cancatenate in one step, kinda like this:
> a.length = b.length + c.length + d.length;
> a[0                   .. b.length] = b;
> a[b.length            .. c.length] = c;
> a[b.length + c.length .. d.length] = d;
> 
> ..instead of working like this:
> a = (b ~ c) ~ d;
> 
> It would be faster because it involves less copying and allocation, right?
> 
> Does the D language spec allow concatenation to be implemented that way? or does it require something like a strict left to right order of operations, one concatenation operator at a time? How do dmd and gdc do it?
> 
I don't know with respect to D, but the Euphoria language recently made this optimization and it did shave off a lot wasted time. A common idiom is inserting an item ...

  A = A[0 .. x] ~ newitem ~ A[x .. $];

which greatly benefits from this optimization.

-- 
Derek
Melbourne, Australia
20/04/2005 9:44:52 AM

I an into trouble trying to do things like that and wasn't even sure why. Should work... would be more intuitive.

TZ

"Sterling Christensen" <Sterling_member@pathlink.com> wrote in message news:d444es$1qob$1@digitaldaemon.com...
> I guess this is a feature request.
>
> Say you've got:
> char[] a, b, c, d;
>
> I think that this:
> a = b ~ c ~ d;
>
> ..should cancatenate in one step, kinda like this:
> a.length = b.length + c.length + d.length;
> a[0                   .. b.length] = b;
> a[b.length            .. c.length] = c;
> a[b.length + c.length .. d.length] = d;
>
> ..instead of working like this:
> a = (b ~ c) ~ d;
>
> It would be faster because it involves less copying and allocation, right?
>
> Does the D language spec allow concatenation to be implemented that way? or does it require something like a strict left to right order of operations, one concatenation operator at a time? How do dmd and gdc do it?
>
> -Sterling