C ++ Templates Chapter 1 Templates and inheritance examples

[Cpp]
# Include <iostream>
 
Using namespace std;
 
// Intermediate Template
Template <typename Base, int D>
Class Discrim: public Base
{
Public:
Discrim (){
Cout <"Discrim ()" <endl;
}

};
 
// The PolicySelector of the Discrim class can be inherited from the same base class multiple times.
Template <typename set1, typename set2, typename set3, typename set4>
Class PolicySelector: public Discrim <set1, 1>, public Discrim <set2, 2>, public Discrim <set3, 3>, public Discrim <set4, 4>
{
};
 
Class DefaultPol1 {
Public:
Void print (){
Cout <"p1 print ()" <endl;
}
};
 
Class DefaultPol2 {
Public:
Void print (){
Cout <"p2 print ()" <endl;
}
};
 
Class DefaultPol3 {
Public:
Void print (){
Cout <"p3 print ()" <endl;
}
};
 
Class DefaultPol4 {
Public:
Void print (){
Cout <"p4 print ()" <endl;
}
};
 
// Create a set of default values
Class DefaultPols
{
Public:
Typedef DefaultPol1 dp1;
Typedef DefaultPol2 dp2;
Typedef DefaultPol3 dp3;
Typedef DefaultPol4 dp4;
};
 
Class DefaultPolArgs: virtual public DefaultPols {};
 
// Write several templates to overwrite the Default policy parameters.
// 1
Template <typename Policy>
Class policypolicis: virtual public DefaultPols
{
Public:
Typedef Policy dp1;

Virtual void print (){
Dp1 dd;
Dd. print ();
}
};
 
// 2
Template <typename Policy>
Class Policy2_is: virtual public DefaultPols
{
Public:
Typedef Policy dp2;

Virtual void print (){
Dp1 dd;
Dd. print ();
}
};
 
// 3
Template <typename Policy>
Class Policy3_is: virtual public DefaultPols
{
Public:
Typedef Policy dp3;

Policy3_is (){
Cout <"Policy3_is ()" <endl;
}

Virtual void print (){
Dp1 dd;
Dd. print ();
}
};
 
// 4
Template <typename Policy>
Class Policy4_is: virtual public DefaultPols
{
Public:
Typedef Policy dp4;

Virtual void print (){
Dp1 dd;
Dd. print ();
}
};
 
// All the default values here are the same
Template <typename PolicySet1 = DefaultPolArgs,
Typename PolicySet2 = DefaultPolArgs,
Typename PolicySet3 = DefaultPolArgs,
Typename PolicySet4 = DefaultPolArgs>
Class BreadSlicer
{
Public:
// Create a selector. PolicySelector uses the template parameters to initialize them as the corresponding type.
// In this way, the parent class of PolicySelector is specified, and it is inherited from its own template parameters...
// The understanding of this part is not clear yet ??
Typedef PolicySelector <PolicySet1, PolicySet2, PolicySet3, PolicySet4> policies;

Void print (){
Typename policies: dp1 p1;
P1.print ();
 
Typename policies: dp2 p2;
P2.print ();

Typename policies: dp3 p3;
P3.print ();

Typename policies: dp4 p4;
P4.print ();
}

};
 
Class CustomPoliA
{
Public:
Void print (){
Cout <"CustomPoliA print ()" <endl;
}

};
 
Class CustomPoliB
{
Public:
Void print (){
Cout <"CustomPoliB print ()" <endl;
}

};
 
Int main (int argc, char ** argv)
{
BreadSlicer <Policy3_is <CustomPoliA>, Policy4_is <CustomPoliB> bc;
Bc. print ();

Return 0;
}
 
 
Starting:/home/Robert tkun/projects/tevent/build/tevent
P1 print ()
P2 print ()
CustomPoliA print ()
CustomPoliB print ()
* ** Exited normally ***