void main()
{
      import std.utf;
      decode("dlang", 1);
}

Error: template std.utf.decode cannot deduce function from
argument types !()(string, int), candidates are:
D:\msc\D\dmd2\windows\bin\..\..\src\phobos\std\utf.d(924):
std.utf.decode(S)(auto ref S str, ref size_t index) if
(!isSomeString!S && isRandomAccessRange!S && hasSlicing!S &&
hasLength!S && isSomeChar!(ElementType!S))
D:\msc\D\dmd2\windows\bin\..\..\src\phobos\std\utf.d(942):
std.utf.decode(S)(auto ref S str, ref size_t index) if
(isSomeString!S)

why doesn't "decode(S)(auto ref S str, ref size_t index) if
(isSomeString!S)" correspond?

On Thursday, 18 September 2014 at 06:09:54 UTC, Algo wrote:
> void main()
> {
>       import std.utf;
>       decode("dlang", 1);
> }
>
> Error: template std.utf.decode cannot deduce function from
> argument types !()(string, int), candidates are:
> D:\msc\D\dmd2\windows\bin\..\..\src\phobos\std\utf.d(924):
> std.utf.decode(S)(auto ref S str, ref size_t index) if
> (!isSomeString!S && isRandomAccessRange!S && hasSlicing!S &&
> hasLength!S && isSomeChar!(ElementType!S))
> D:\msc\D\dmd2\windows\bin\..\..\src\phobos\std\utf.d(942):
> std.utf.decode(S)(auto ref S str, ref size_t index) if
> (isSomeString!S)
>
> why doesn't "decode(S)(auto ref S str, ref size_t index) if
> (isSomeString!S)" correspond?

rvalues cannot be ref it seems

On 09/17/2014 11:23 PM, Algo wrote:
> On Thursday, 18 September 2014 at 06:09:54 UTC, Algo wrote:
>> void main()
>> {
>>       import std.utf;
>>       decode("dlang", 1);
>> }
>>
>> Error: template std.utf.decode cannot deduce function from
>> argument types !()(string, int), candidates are:
>> D:\msc\D\dmd2\windows\bin\..\..\src\phobos\std\utf.d(924):
>> std.utf.decode(S)(auto ref S str, ref size_t index) if
>> (!isSomeString!S && isRandomAccessRange!S && hasSlicing!S &&
>> hasLength!S && isSomeChar!(ElementType!S))
>> D:\msc\D\dmd2\windows\bin\..\..\src\phobos\std\utf.d(942):
>> std.utf.decode(S)(auto ref S str, ref size_t index) if
>> (isSomeString!S)
>>
>> why doesn't "decode(S)(auto ref S str, ref size_t index) if
>> (isSomeString!S)" correspond?
>
> rvalues cannot be ref it seems

Yes. Interestingly, in D rvalues cannot be bound even to const ref.

void main()
{
    import std.stdio;
    import std.utf;

    size_t index = 1;
    dchar decoded = decode("dlang", index);

    writefln("decoded '%s', next character is at index %s.",
             decoded, index);
}

The output:

decoded 'l', next character is at index 2.

Ali

On Thursday, 18 September 2014 at 06:09:54 UTC, Algo wrote:
> void main()
> {
>       import std.utf;
>       decode("dlang", 1);
> }
>
> Error: template std.utf.decode cannot deduce function from
> argument types !()(string, int), candidates are:
> D:\msc\D\dmd2\windows\bin\..\..\src\phobos\std\utf.d(924):
> std.utf.decode(S)(auto ref S str, ref size_t index) if
> (!isSomeString!S && isRandomAccessRange!S && hasSlicing!S &&
> hasLength!S && isSomeChar!(ElementType!S))
> D:\msc\D\dmd2\windows\bin\..\..\src\phobos\std\utf.d(942):
> std.utf.decode(S)(auto ref S str, ref size_t index) if
> (isSomeString!S)
>
> why doesn't "decode(S)(auto ref S str, ref size_t index) if
> (isSomeString!S)" correspond?

I was having same issue a while ago. But I realized I was using function in the wrong way with string type and passing a size_t in the 2th argument. You can see use of decode(val, size) in the standard library but call it in your code result in an error.

it worked:

string s = readText("file");
decode(cast(ubyte[]) s);

I'm not sure why you're trying to pass a string literal as argument because it does need a memory location to change to new memory location, where bytes skiped end. That's why it does use ref.