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Guest
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 Posted: Sun May 13, 2007 9:11 am Post subject: Function template type inference doesn't work with inheritan |
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I'm having a problem getting derived types to be inferred as valid
parameters by a function template.
template <typename T>
struct Base {}
template<typename T>
struct Derived : public Base<T> {}
template <typename T>
void fn(Base<T>* b) { }
When I call fn with a Derived<int>* gcc gives me the error "no
matching function for call to..."
Is there any way to get the function template to accept derived
objects?
Thanks,
Alex Rubinsteyn |
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Gianni Mariani
Guest
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| Posted: Sun May 13, 2007 9:11 am Post subject: Re: Function template type inference doesn't work with inher |
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On May 13, 4:50 pm, MikhailGorbac...@gmail.com wrote:
| Quote: | I'm having a problem getting derived types to be inferred as valid
parameters by a function template.
template <typename T
struct Base {}
template<typename T
struct Derived : public Base<T> {}
template <typename T
void fn(Base<T>* b) { }
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// strictly not want you want but might do
template <typename X>
void fn(X* x)
{
Base<T>* b( x );
....
}
Or add this method - at least you know that it's only the derived ones
that you're getting
template <typename T>
void fn(Derived<T>* x)
{
Base<T> * b = x;
fn( b );
}
Or - hack but does the job - breaks some non-compliant compilers
// strictly not want you want but might do
template <typename X>
void fn(X* x, Convertible<X *, Base<T> *>::type = 0 )
{
Base<T>* b( x );
fn(b);
}
where Convertible is a special template class to determine if the type
of X is one of the types you allow be used - it's probably overkill
for this case.
| Quote: |
When I call fn with a Derived<int>* gcc gives me the error "no
matching function for call to..."
Is there any way to get the function template to accept derived
objects?
Thanks,
Alex Rubinsteyn |
|
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| Back to top |
|
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