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List parameters

user@domain.invalid
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#1: Oct 22 '06
Hi,

I try this code:

template <typename Tinline
T const& max(T const& a, T const& b)
{
return a<b?b:a;
}

template <typename T, ... listinline
T const& max(T const& a, T const& b, list const& x)
{
return max(a, max(b, x));
}


But it not compile.
I have this message:
"error: expected identifier before '...' token"

I saw this sample in book "c++ templates: the complete guide"
i use wxWidgets with gcc compiler.

Is this code legal? is it compile?
If no how use list parameters in template?

Thunks
David Harmon
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#2: Oct 22 '06

re: List parameters


On Sun, 22 Oct 2006 02:06:20 +0200 in comp.lang.c++,
user@domain.invalid wrote,
Quote:
> template <typename T, ... listinline
> T const& max(T const& a, T const& b, list const& x)
> {
return max(a, max(b, x));
> }
No, the ... is not at all allowed there.
This is from chapter 13, "Future Directions", where the authors are
discussing things that don't exist yet, but might in the future,
right???

Lahsen
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Posts: n/a
#3: Oct 22 '06

re: List parameters


David Harmon a écrit :
Quote:
On Sun, 22 Oct 2006 02:06:20 +0200 in comp.lang.c++,
user@domain.invalid wrote,
>
Quote:
>> template <typename T, ... listinline
>> T const& max(T const& a, T const& b, list const& x)
>> {
> return max(a, max(b, x));
>> }
>
>
No, the ... is not at all allowed there.
This is from chapter 13, "Future Directions", where the authors are
discussing things that don't exist yet, but might in the future,
right???
>
Ok,
Thunks.

I try to do it with typeListe technique in modern c++.

But there'is function ellipsis like:

void f(int ...);

f(1, 2, 3);
f(45, 68 ,2 ,64 ,3598);

that compile. But it's not easy to use argument of this function.

loufoque
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#4: Oct 22 '06

re: List parameters


Lahsen wrote:
Quote:
>
But there'is function ellipsis like:
>
void f(int ...);
>
f(1, 2, 3);
f(45, 68 ,2 ,64 ,3598);
>
that compile. But it's not easy to use argument of this function.
That's a runtime thing which isn't type-safe at all.
It should be avoided.
loufoque
Guest
 
Posts: n/a
#5: Oct 22 '06

re: List parameters


user@domain.invalid wrote:
Quote:
Hi,
>
I try this code:
>
template <typename Tinline
T const& max(T const& a, T const& b)
{
return a<b?b:a;
}
>
template <typename T, ... listinline
T const& max(T const& a, T const& b, list const& x)
{
return max(a, max(b, x));
}
>
>
But it not compile.
You might want to play around with variadic templates, a proposal for
the next C++ standard which will allow what you want.
There is already a patch to implement it in GCC.
Closed Thread