Template argument deduction and function pointers

[Tobias Müller]

template <typename R, typename P1, typename P2, R (*f)(P1,P2)>
class MyClass
{
R myMethod(P1 param1, P2 param2);
};

This works, however I must always specify all the template arguments R, P1,
and P2, even if those could always be deduced from the 4th argument f:

int fun(double a, int b);

MyClass<int, double, int, &fun> myObject;
int c = myObject.myMethod(1.0, 2);

But I want some different template such that I can write:

MyClass<&fun> myObject;

All the information about R, P1, and P2 is already implicitly there.

Tobi

 

[88888 Dihedral]

template <typename R, typename P1, typename P2, R (*f)(P1,P2)>
class MyClass
{
R myMethod(P1 param1, P2 param2);
};

This works, however I must always specify all the template arguments R, P1,
and P2, even if those could always be deduced from the 4th argument f:

int fun(double a, int b);

MyClass<int, double, int, &fun> myObject;
int c = myObject.myMethod(1.0, 2);

But I want some different template such that I can write:

MyClass<&fun> myObject;

All the information about R, P1, and P2 is already implicitly there.

Tobi

There's no saving in typing.
Just use a functor in c elegantly.

 

[Tobias Müller]

There's no saving in typing.
Just use a functor in c elegantly.

Of course not, if the function always has the same signature. But I don't
want to define a class for every function signature I use in that way,
especially if I can (potentially) solve it via a template.

Tobi

 

[88888 Dihedral]

Of course not, if the function always has the same signature. But I don't
want to define a class for every function signature I use in that way,
especially if I can (potentially) solve it via a template.

Tobi

http://www.newty.de/fpt/fpt.html

Check the true functional c /c++!

 

[Tobias Müller]

http://www.newty.de/fpt/fpt.html

Check the true functional c /c++!

Have you also read chapter 4? (about functors)

The setup that I posted is just to illustrate my point, not exactly what I
am using.
It's not restricted to functions, also methods should be possible.

Tobi

 

[88888 Dihedral]

Have you also read chapter 4? (about functors)

The setup that I posted is just to illustrate my point, not exactly what I
am using.
It's not restricted to functions, also methods should be possible.

Tobi

I use a function pointer int (*hooker)() in most applications.
It is the programmer's job to hook the correct address of a function to
the hooker.

Also the argument to be used must be programmed right.

There are situations that the hookers are in a library that will be hooked
by users other than the author of the library.

Then please check the functionoid that requires specific arguments in the
run time.

 

[Heinz Ozwirk]

"88888 Dihedral" schrieb im Newsbeitrag

I use a function pointer int (*hooker)() in most applications.
It is the programmer's job to hook the correct address of a function to
the hooker.

OT: Don't use rules of your native language to invent new words in foreign
languages. Lookup the meaning of hooker in a dictionary (like leo.org).

Sorry for being off topic, but I simply couldn't resist.
Heinz

 

[Tobias Müller]

If you have a C++11 compiler you could perhaps write a make function and
make use of the auto keyword:

auto myObject = make_MyClass(&fun);
int c = myObject.myMethod(1.0, 2);

HTH.

/Leigh

That would probably work but I cannot use c++11 features, and second, I
want to use the objects mainly as members of other classes, so auto
wouldn't work anyway in that context.

Tobi

 

[Tobias Müller]

I use a function pointer int (*hooker)() in most applications.
It is the programmer's job to hook the correct address of a function to
the hooker.

Also the argument to be used must be programmed right.

There are situations that the hookers are in a library that will be hooked
by users other than the author of the library.

Then please check the functionoid that requires specific arguments in the
run time.

Well I have a working and type safe solution, it is just a bit verbose. But
I certainly don't want to lose those features.

Tobi

 

[Joe keane]

It's actually a rugby position.

Maybe he should use 'flange'?

TO

 

[Ian Collins]

It's actually a rugby position.

What is?

Context!

 

[gwowen]

What is?

Context!

The problem is he deleted the first 5/8 of the post...

 

[Nobody]

What is?

"Hooker" is the centre-forward position in rugby (union and league).