On Friday, 27 March 2015 at 14:24:47 UTC, Shammah Chancellor
wrote:
On 2015-03-26 01:04:03 +0000, Freddy said:
On Thursday, 26 March 2015 at 00:11:05 UTC, Dicebot wrote:
On Wednesday, 25 March 2015 at 22:12:04 UTC, Freddy wrote:
"D-style Variadic Functions" found
here:http://dlang.org/function.html seem entirely out
classed by Variadic Function Templates. Can we deprecate
them?
Those are two different concepts with different trade-offs.
Using variadic templates adds template bloat. Using D-style
variadics requires RTTI (and small overhead for it). It is up
to library/application writer to decide what is best in his
case.
My ploblem is that Variadic Function shouldn't be builtin the
language. They are rarely need and can be abstracted into a
library. Something like this:
```
import core.stdc.stdlib: alloca;
import std.stdio;
template VariadicFunction(alias Imp){
auto VariadicFunction(T...)(T args){
enum size=T.length * TypeInfo.sizeof;
auto rtti=cast(TypeInfo[])(alloca(size)[0..size]);
foreach(i,type;T){
rtti[i]=typeid(type);
}
//auto data=&args; bug? doesn't work
void* data;
{
size_t datasize;//T.sizeof doesn't work
foreach(type;T){
datasize+=type.sizeof;
}
data=alloca(datasize);
size_t inc;
foreach(v;args){
*cast(typeof(v)*)(data+inc)=v;
inc+=v.sizeof;
}
}
Imp(data,rtti);
}
}
private void rtVariadicImp(void* vars,scope const TypeInfo[]
rtinfo){
writeln(*cast(int*)vars);
writeln(rtinfo);
}
alias rtVariadic=VariadicFunction!(rtVariadicImp);
void main(){
rtVariadic(1,'a');
}
```
I disagree, and your example does not get rid of the template
bloat. That does in fact instantiate a template for every set
of argument types.
-Shammah
To be fair, this is most likely going to be inlined an ditched
away with any decent optimizer.
