Re: Setting defaults to variadic template args
On 2012-10-02 15:15, Manu wrote:
Is it possible?
Eg:
struct Event(T... = (int, float))
{
void F(T...); // - should default to F(int, float)
}
Does anyone have any clever tricks that will work in this scenario? Some
magic tuple syntax?
struct Event
{
static if (T.length == 0)
void F(int, float);
else
void F(T);
}
Perhaps?
--
/Jacob Carlborg
Re: Setting defaults to variadic template args
module program;
import std.stdio;
import std.traits;
import std.typetuple;
struct Event (T...) {
alias EraseAll!(void, TypeTuple!(T,
Select!(T.length 1, int, void),
Select!(T.length 2, float, void),
)) T2;
void F (T2 args) {
writeln(typeid(typeof(args)));
}
}
void main () {
Event!() e1;
e1.F(5, 6);
}
On Tuesday, 2 October 2012 at 13:15:08 UTC, Manu wrote:
Is it possible?
Eg:
struct Event(T... = (int, float))
{
void F(T...); // - should default to F(int, float)
}
Does anyone have any clever tricks that will work in this
scenario? Some
magic tuple syntax?
Re: Setting defaults to variadic template args
On 2 October 2012 16:24, Andrej Mitrovic andrej.mitrov...@gmail.com wrote:
On 10/2/12, Manu turkey...@gmail.com wrote:
Does anyone have any clever tricks that will work in this scenario? Some
magic tuple syntax?
Without resorting to helper templates I only know of using this internal
trick:
struct Event(Args...)
{
static if (Args.length)
alias Args T;
else
alias TypeTuple!(int, float) T;
void F(T t) { }
}
Also there's a somewhat related bug but for variadic template
functions with default arguments:
http://d.puremagic.com/issues/show_bug.cgi?id=8687
I think this is fine for my needs. Thanks!
Re: Setting defaults to variadic template args
Or maybe... This seems like a much better solution:
module program;
import std.stdio;
import std.traits;
import std.typetuple;
template SelectTrue (bool condition, T) {
static if (condition)
alias T SelectTrue;
}
struct Event (T...) {
alias TypeTuple!(T,
SelectTrue!(T.length 1, int),
SelectTrue!(T.length 2, float),
) T2;
void F (T2 args) {
writeln(typeid(typeof(args)));
}
}
void main () {
Event!() e1;
e1.F(5, 6);
}
On Tuesday, 2 October 2012 at 13:44:10 UTC, luka8088 wrote:
module program;
import std.stdio;
import std.traits;
import std.typetuple;
struct Event (T...) {
alias EraseAll!(void, TypeTuple!(T,
Select!(T.length 1, int, void),
Select!(T.length 2, float, void),
)) T2;
void F (T2 args) {
writeln(typeid(typeof(args)));
}
}
void main () {
Event!() e1;
e1.F(5, 6);
}
On Tuesday, 2 October 2012 at 13:15:08 UTC, Manu wrote:
Is it possible?
Eg:
struct Event(T... = (int, float))
{
void F(T...); // - should default to F(int, float)
}
Does anyone have any clever tricks that will work in this
scenario? Some
magic tuple syntax?
Re: Setting defaults to variadic template args
And the simplest solution wins:
module program;
import std.stdio;
import std.traits;
import std.typetuple;
struct Event (T1 = int, T2 = float, Telse...) {
alias TypeTuple!(T1, T2, Telse) T;
void F (T args) {
writeln(typeid(typeof(args)));
}
}
void main () {
Event!() e1;
e1.F(5, 6);
}
I hope that you found the solution that you where looking for.
On Tuesday, 2 October 2012 at 13:49:56 UTC, luka8088 wrote:
Or maybe... This seems like a much better solution:
module program;
import std.stdio;
import std.traits;
import std.typetuple;
template SelectTrue (bool condition, T) {
static if (condition)
alias T SelectTrue;
}
struct Event (T...) {
alias TypeTuple!(T,
SelectTrue!(T.length 1, int),
SelectTrue!(T.length 2, float),
) T2;
void F (T2 args) {
writeln(typeid(typeof(args)));
}
}
void main () {
Event!() e1;
e1.F(5, 6);
}
On Tuesday, 2 October 2012 at 13:44:10 UTC, luka8088 wrote:
module program;
import std.stdio;
import std.traits;
import std.typetuple;
struct Event (T...) {
alias EraseAll!(void, TypeTuple!(T,
Select!(T.length 1, int, void),
Select!(T.length 2, float, void),
)) T2;
void F (T2 args) {
writeln(typeid(typeof(args)));
}
}
void main () {
Event!() e1;
e1.F(5, 6);
}
On Tuesday, 2 October 2012 at 13:15:08 UTC, Manu wrote:
Is it possible?
Eg:
struct Event(T... = (int, float))
{
void F(T...); // - should default to F(int, float)
}
Does anyone have any clever tricks that will work in this
scenario? Some
magic tuple syntax?
Re: Setting defaults to variadic template args
On 2 October 2012 16:45, Manu turkey...@gmail.com wrote:
On 2 October 2012 16:24, Andrej Mitrovic andrej.mitrov...@gmail.comwrote:
On 10/2/12, Manu turkey...@gmail.com wrote:
Does anyone have any clever tricks that will work in this scenario? Some
magic tuple syntax?
Without resorting to helper templates I only know of using this internal
trick:
struct Event(Args...)
{
static if (Args.length)
alias Args T;
else
alias TypeTuple!(int, float) T;
void F(T t) { }
}
Also there's a somewhat related bug but for variadic template
functions with default arguments:
http://d.puremagic.com/issues/show_bug.cgi?id=8687
I think this is fine for my needs. Thanks!
Actually, this leaves a problem...
Distinction between:
Event x; // using defaults
and
Event!() x; // explicitly selecting none (which would fall back to the
defaults)
Is such a distinction possible? I presume not...
Re: Setting defaults to variadic template args
On 10/2/12, Manu turkey...@gmail.com wrote: Actually, this leaves a problem... Distinction between: Event x; // using defaults and Event!() x; // explicitly selecting none (which would fall back to the defaults) Is such a distinction possible? I presume not... Well actually you can't use the first syntax at all with templates or templated types. :/
Re: Setting defaults to variadic template args
On 2 October 2012 18:56, Andrej Mitrovic andrej.mitrov...@gmail.com wrote: On 10/2/12, Manu turkey...@gmail.com wrote: Actually, this leaves a problem... Distinction between: Event x; // using defaults and Event!() x; // explicitly selecting none (which would fall back to the defaults) Is such a distinction possible? I presume not... Well actually you can't use the first syntax at all with templates or templated types. :/ Errr, really? If the template has default args, surely you don't need to specify any template args? I'm sure I've done that before... :/
Re: Setting defaults to variadic template args
On 10/2/12, Manu turkey...@gmail.com wrote: Are you sure it's not fixed? I'm sure I do it all the time... :/ Or I'm smoking some really good stuff. I'd really like to see how you do it. If not, I'll have some of that stuff you're having, thanks. :p
Re: Setting defaults to variadic template args
On 2012-10-02 18:10, Manu wrote: Are you sure it's not fixed? I'm sure I do it all the time... :/ Or I'm smoking some really good stuff. It's not needed for functions templates. But it is needed for type templates. -- /Jacob Carlborg
Re: Setting defaults to variadic template args
On 10/02/2012 03:15 PM, Manu wrote:
struct Event(T... = (int, float))
{
void F(T...); // - should default to F(int, float)
}
template Event(){alias Event!(int,float) Event;}
struct Event(T...){
void F(T...);
}
