• harakim (40/40) Jul 13 2019 I wanted to do this:
• evilrat (15/19) Jul 13 2019 Can't really tell what's going on without call site and what do
• harakim (5/25) Jul 13 2019 Thanks. That answered my question. I was hoping to do this:

harakim <harakim gmail.com> writes:

I wanted to do this:
package int serialize(byte[] destination, int offset, T...)(T 
values)
{	
	static foreach (i, value; values)
	{
		*cast(T[i] *)(destination.ptr + offset) = value;
		offset += typeid(T[i]).tsize();
	}
	
	return offset;
}

But I got this error:
main.d(8): Error: template main.serialize cannot deduce function 
from argument types !()(byte[], int, byte, int), candidates are:
main.d(20):        main.serialize(byte[] destination, int offset, 
T...)(T values)

Eventually, I assumed that you couldn't do heterogeneous 
arguments with other arguments first.

I was able to do this and it works:
package int serialize(T...)(T values)
{
	static assert(values.length >= 2);

	auto ptr = (cast(byte[])values[0]).ptr;
	
	int offset = cast(int)values[1];

	static foreach (i, value; values)
	{
		static if (i > 1)
		{
			*cast(T[i] *)(ptr + offset) = value;
			offset += typeid(T[i]).tsize();
		}
	}
	
	return offset;
}

That is obviously a lot uglier. Can you have a function with 
non-variadic arguments followed by heterogeneous variadic 
arguments?

evilrat <evilrat666 gmail.com> writes:

On Sunday, 14 July 2019 at 03:51:14 UTC, harakim wrote:
 I wanted to do this:
 package int serialize(byte[] destination, int offset, T...)(T 
 values)
 ....

Can't really tell what's going on without call site and what do 
you exactly mean by "heterogeneous arguments with other 
arguments", but this thing is syntax error. You declared a 
template here, and template parameters (compile-time parameters) 
must come first.

    int serialize(T...)(byte[] destination, int offset, T values)

This is the case if you wanted to pass that buffer at runtime, 
not sure if you can do this with CT parameters, though it 
shouldn't prevent you from forcing CTFE evaluation by assigning 
result to another CT parameter or enum.


But if by "other arguments" you mean passing different types 
there is untyped variadics with a bit different behavior(see [1])


[1] 
https://dlang.org/spec/function.html#d_style_variadic_functions

harakim <harakim gmail.com> writes:

On Sunday, 14 July 2019 at 06:05:13 UTC, evilrat wrote:
 On Sunday, 14 July 2019 at 03:51:14 UTC, harakim wrote:
 I wanted to do this:
 package int serialize(byte[] destination, int offset, T...)(T 
 values)
 ....

 Can't really tell what's going on without call site and what do 
 you exactly mean by "heterogeneous arguments with other 
 arguments", but this thing is syntax error. You declared a 
 template here, and template parameters (compile-time 
 parameters) must come first.

    int serialize(T...)(byte[] destination, int offset, T values)

 This is the case if you wanted to pass that buffer at runtime, 
 not sure if you can do this with CT parameters, though it 
 shouldn't prevent you from forcing CTFE evaluation by assigning 
 result to another CT parameter or enum.


 But if by "other arguments" you mean passing different types 
 there is untyped variadics with a bit different behavior(see 
 [1])


 [1] 
 https://dlang.org/spec/function.html#d_style_variadic_functions

Thanks. That answered my question. I was hoping to do this:
int serialize(T...)(byte[] destination, int offset, T values)

And now I understand a lot more about variadic functions and type 
arguments.