On Tuesday, 18 April 2017 at 10:13:09 UTC, Jonathan M Davis wrote:
On Monday, April 17, 2017 07:23:50 Jonathan M Davis via
Digitalmars-d-learn wrote:
So, if you're okay with explicitly instantiating your variadic
function template instead of having the types inferred, then
it can work, but otherwise, no. Making it work would require a
language enhancement
Actually, not only is there already a bug report for this
https://issues.dlang.org/show_bug.cgi?id=8687
which is marked as a bug and not an enhancement, and when
Walter commented on it when an ICE related to it was fixed, he
didn't change it from a bug to an enhancement. So, it looks
like he agrees that it's a bug rather than considering it an
enhancement. It has yet to be fixed regardless though.
- Jonathan M Davis
import std.stdio: writeln;
import std.conv: to;
void main()
{
add("Scene 1", "Scene 2", "Scene 3");
add("Scene 3", "Scene 4", "Scene 5");
add(5, 6, 7);
add(7, "Scene 8", "Scene 9");
writeln("total scenes added: ", sceneCount);
}
struct Scene
{
string name;
string file;
size_t line;
}
Scene*[] listOfScenes;
int[string] indexOfScenes;
int sceneCount = 0;
void add_impl(T...)(string file, size_t line, T args)
{
foreach(arg; args)
{
static if (is(typeof(arg) == string))
{
auto name = arg;
}
else
{
auto name = "Scene " ~ arg.to!string;
}
if (name in indexOfScenes)
{
EError(file, line, "scene already exists", name);
}
else
{
indexOfScenes[name] = sceneCount;
listOfScenes ~= new Scene(name, file, line);
sceneCount += 1;
writeln("added " ~ name);
}
}
}
void add(string file = __FILE__, size_t line = __LINE__, T...)(T
args)
{
add_impl!T(file, line, args);
}
void EError(string file, size_t line, string message, string name)
{
writeln(name, ": ", message,
" in file ", file, " in line ", line);
auto previous = listOfScenes[indexOfScenes[name]];
writeln("previous definition of ", previous.name,
" was in ", previous.file, " in line ",
previous.line);
}
/* output:
added Scene 1
added Scene 2
added Scene 3
Scene 3: scene already exists in file vlf.d in line 7
previous definition of Scene 3 was in vlf.d in line 6
added Scene 4
added Scene 5
Scene 5: scene already exists in file vlf.d in line 8
previous definition of Scene 5 was in vlf.d in line 7
added Scene 6
added Scene 7
Scene 7: scene already exists in file vlf.d in line 9
previous definition of Scene 7 was in vlf.d in line 8
added Scene 8
added Scene 9
total scenes added: 9
*/
I tried to produce an example of calling a function with
variadic template arguments using special tokens __FILE__ and
__LINE__.
This compiles and runs, producing the output shown, using the
default gdc
provided by Ubuntu 17.04. This appears to be a workaround for
Issue 8687.
The instantiations of the wrapper function `add` should only add
minimally
to the compiled object code size, once per call of `add`.
I'm not sure about the quality of any of this code.
