• Jack Applegame (13/13) May 22 2013 Hello.
• Jack Applegame (9/9) May 22 2013 I found awkward solution:
• bearophile (6/15) May 22 2013 I think that's essentially the right solution. I suggest to
• Jack Applegame (3/6) May 22 2013 Yes.
• bearophile (21/22) May 22 2013 I suggest to use indents composed by 4 spaces.

"Jack Applegame" <japplegame gmail.com> writes:

Hello.

I need a template for casting arrays to another type without 
changing const and immutable attributes:

template ByteType(T) {
   // some magic
}

const(int)[] ca;
immutable(short)[] is;
long[] ml;

static assert(is(ByteType!ca == const(byte)[]));
static assert(is(ByteType!is == immutable(byte)[]));
static assert(is(ByteType!ml == byte[]));

What kind of template magic I should use?

"Jack Applegame" <japplegame gmail.com> writes:

I found awkward solution:

template ByteType(alias t) {
   alias typeof(t) T;
   static if(is(ElementType!T == const)) alias const(byte)[] 
ByteType;
   else static if(is(ElementType!T == immutable)) alias 
immutable(byte)[] ByteType;
   else alias byte[] ByteType;
}

"bearophile" <bearophileHUGS lycos.com> writes:

Jack Applegame:

 I found awkward solution:

 template ByteType(alias t) {
   alias typeof(t) T;
   static if(is(ElementType!T == const)) alias const(byte)[] 
 ByteType;
   else static if(is(ElementType!T == immutable)) alias 
 immutable(byte)[] ByteType;
   else alias byte[] ByteType;
 }

I think that's essentially the right solution. I suggest to 
generalize it a bit, removing the byte from its insides, and 
making it a template argument. I think "shared" is missing.

Bye,
bearophile

"Jack Applegame" <japplegame gmail.com> writes:

On Wednesday, 22 May 2013 at 13:01:26 UTC, bearophile wrote:
 I think that's essentially the right solution. I suggest to 
 generalize it a bit, removing the byte from its insides, and 
 making it a template argument. I think "shared" is missing.

Yes.

Finally http://dpaste.1azy.net/fc503331

"bearophile" <bearophileHUGS lycos.com> writes:

Jack Applegame:

 Finally http://dpaste.1azy.net/fc503331

I suggest to use indents composed by 4 spaces.
Generally in D we use template constraints, instead of static ifs 
with a nice error message...
In such complex situations I also suggest to add braces.

Something like this:


auto castElementType(T = byte, F)(ref F from)
if (isArray!F) {
     alias E = typeof(from[0]);

     static if(is(E == const)) {
         return cast(const(Unqual!T)[])from;
     } else static if(is(E == immutable)) {
         return cast(immutable(Unqual!T)[])from;
     } else static if(is(E == shared)) {
         return cast(shared(Unqual!T)[])from;
     } else {
         return cast(Unqual!T[])from;
     }
}


Bye,
bearophile