On Tuesday, 15 July 2014 at 00:19:15 UTC, Ali Çehreli wrote:
On 07/14/2014 05:10 PM, Ali Çehreli wrote:
> On 07/14/2014 04:04 PM, H. S. Teoh via Digitalmars-d-learn
wrote:
>
> > On Mon, Jul 14, 2014 at 09:12:30PM +0000, Klb via
Digitalmars-d-learn
> wrote:
> >> hello what is the right syntax for this:
> >>
> >> ----------------------------------------------------
> >> import std.stdio, std.conv;
> >>
> >> void main(string args[])
> >> {
> >> ubyte[3] src = [0, 1, 2];
> >> string trg = "";
> >>
> >> @property ubyte[3] srcAsProp(){return src;}
> >>
> >> // Error: template std.conv.to cannot deduce
function from
> argument types
> >> // !(string)(ubyte[3]), candidates are:
> >> trg = to!(string)(srcAsProp());
> >> }
> >> ----------------------------------------------------
> >>
> >> In a real-world application I'd use an intermediate value
but I'd like
> >> to know If it's possible...The strange fact is that it
doesn't trig an
> >> error if src is a dyn. array. (if you remove the 3 from
[3] then it
> >> passes).
> >
> > You need to slice the static array:
> >
> > trg = to!string(srcAsProp()[]);
>
> There seems to be an attempt in Phobos to support it without
needing an
> explicit slice.
>
> From std/phobos/conv.d:
I meant phobos/std/conv.d there.
> /*
> Converting static arrays forwards to their dynamic
counterparts.
> */
> T toImpl(T, S)(ref S s)
> if (isRawStaticArray!S)
Ok, I think I see now (after two minutes after posting it :) )
why it doesn't work. The overload above takes by-ref, which
does not bind to rvalues in D.
And the problem is, what srcAsProp() returns is an rvalue
because static arrays are value-types and they get copied.
> {
> return toImpl!(T, typeof(s[0])[])(s);
> }
>
> @safe pure nothrow unittest
> {
> char[4] test = ['a', 'b', 'c', 'd'];
> static assert(!isInputRange!(Unqual!(char[4])));
> assert(to!string(test) == test);
> }
>
> I don't know why that overload does not take care of OP's
case. (I am be
> completely off here. :) )
I hope I have it now. :p
Ali
Thanks for this accurate explanation. The problem is quite clear
now.
