typename vs class

[EvilOldGit]

Are these just aliases ?
A few docs I've read imply that in certain case they aren't identical.

[Alf P. Steinbach]

* Ev********@googlemail.com:

Are these just aliases ?

No.

A few docs I've read imply that in certain case they aren't identical.

In a template parameter list they are identical, in all other cases they
aren't identical.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[blangela]

On Mar 19, 11:26 am, "Alf P. Steinbach" <[e-mail]:

* [e-mail]:

Are these just aliases ?

No.

A few docs I've read imply that in certain case they aren't identical.

In a template parameter list they are identical, in all other cases they
aren't identical.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

Where is typename used other than in a template paramater list?

[Marcus Kwok]

blangela <Bo***********@telus.netwrote:

On Mar 19, 11:26 am, "Alf P. Steinbach" <[e-mail]:

>In a template parameter list they are identical, in all other cases they
aren't identical.

Where is typename used other than in a template paramater list?

One example is in disambiguating dependant names, e.g.,

template <typename T>
class xyz {
void foo()
{
typename T::x my_x;
}
};

(example modified from
http://www.comeaucomputing.com/techt...ates/#typename
which is a handy reference)

--
Marcus Kwok
Replace 'invalid' with 'net' to reply

[Fei Liu]

blangela wrote:

On Mar 19, 11:26 am, "Alf P. Steinbach" <[e-mail]:

>* [e-mail]:

>>Are these just aliases ?

No.

>>A few docs I've read imply that in certain case they aren't identical.

In a template parameter list they are identical, in all other cases they
aren't identical.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

Where is typename used other than in a template paramater list?

Consider typename a more generic form to declare template parameters.
Use typename whenever you can instead of class.

Of course when you declare a class data structure, use 'class'. Only
place I am aware of that typename cannot replace class keyword.

Fei

[kwikius]

On 19 Mar, 19:19, Fei Liu <[e-mail]:

Of course when you declare a class data structure, use 'class'. Only
place I am aware of that typename cannot replace class keyword.

Other place is template template params e.g:

// for allocator
#include <memory>

// can't replace 'class' with typename below
template <template<typename, typenameclass Seq>
struct F{

template <typename T>
void foo( Seq<T,std::allocator<T const & seq)
{
std::cout << *seq.begin() <<'\n';
}
};

#include <vector>
#include <iostream>

int main()
{
std::vector<intx;
F<std::vectorf;

x.push_back(1);

f.foo(x);

}

regards
Andy Little

[=?ISO-8859-1?Q?Erik_Wikstr=F6m?=]

On 2007-03-19 19:26, Alf P. Steinbach wrote:

* Ev********@googlemail.com:

>Are these just aliases ?

No.

>A few docs I've read imply that in certain case they aren't identical.

In a template parameter list they are identical, in all other cases they
aren't identical.

There's also a case where you must use class instead of template, I ran
into this some time ago:

template<template<typename Tclass U>

--
Erik Wikström

[=?ISO-8859-1?Q?Erik_Wikstr=F6m?=]

On 2007-03-19 21:42, Erik Wikström wrote:

On 2007-03-19 19:26, Alf P. Steinbach wrote:

>* Ev********@googlemail.com:

>>Are these just aliases ?

No.

>>A few docs I've read imply that in certain case they aren't identical.

In a template parameter list they are identical, in all other cases they
aren't identical.

There's also a case where you must use class instead of template, I ran
into this some time ago:

template<template<typename Tclass U>

I meant 'use class instead of typename'.

--
Erik Wikström