I would like to know if the following is allowed:
template < class C >
void function(C&);
void function() {
class {} local;
function(local);
}
thanks
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2 Answers
It's not allowed right now. But it's supported in C++0x. The current Standard says at 14.3.1/2
A local type, a type with no linkage, an unnamed type or a type compounded from any of these types shall not be used as a template-argument for a template type-parameter.
That said, if the function is also local, there's no problem
void f() {
class L {} local;
struct C {
static void function(L &l) {
// ...
}
};
C::function(local);
}
answered Apr 18, 2010 at 15:56
Johannes Schaub - litb
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3 Comments
Anycorn
bummers. Is there clean alternative for named tuples (which is what been trying to do)?
Anycorn
Ah. I think local function will do it for me. Thanks
Johannes Schaub - litb
You mean
class { int a; int b; } x; function(x); ? Not possible: the type of x is local. You have to go your way with pair, or make x's class not local (the variable x can still be local). Put the class into an unnamed namespace for example. I usually consider functions inside local classes like this a bit hacky :) But i'm glad i could be of help.It's allowed if you use polymorphism instead of templates. Or if you don't need to extend the interface seen by function, simple inheritance will do.
void function( ABC & );
void function() {
class special : public ABC {
virtual void moof() {}
} local;
function(local);
}
