Combined with the knowledge of the Internet, the specification mode is realized by C + +

Specification.h

#pragma once

Template<class t>
Class ISpecification
{
Public
virtual bool IsSatisfiedBy (T candidate) = 0;
Virtual ispecification<t>* and (ispecification<t>* other) = 0;
Virtual ispecification<t>* Or (ispecification<t>* other) = 0;
Virtual ispecification<t>* not () = 0;
};

Template<class t>
Class Andspecification;
Template<class t>
Class Orspecification;
Template<class t>
Class Notspecification;

Template<class t>
Class Compositespecification:public Ispecification<t>
{
Public
virtual bool IsSatisfiedBy (int candidate) = 0;
Virtual ispecification<t>* and (ispecification<t>* other);
Virtual ispecification<t>* Or (ispecification<t>* other);
Virtual ispecification<t>* not ();
};

Template<class t>
Class Andspecification:public Compositespecification<t>
{
Public
Andspecification (ispecification<t>* x, ispecification<t>* y);
virtual bool IsSatisfiedBy (int candidate);

Private
ispecification<t>* M_one;
ispecification<t>* M_other;
};

Template<class t>
Class Orspecification:public Compositespecification<t>
{
Public
Orspecification (ispecification<t>* x, ispecification<t>* y);
virtual bool IsSatisfiedBy (int candidate);

Private
ispecification<t>* M_one;
ispecification<t>* M_other;
};

Template<class t>
Class Notspecification:public Compositespecification<t>
{
Public
Notspecification (ispecification<t>* x);
virtual bool IsSatisfiedBy (int candidate);
Private
Ispecification<t> *m_wrapped;
};

Specification.cpp

Specification.cpp: Defines the entry point of the console application.
//

#include "Specification.h"

Template<class t>
ispecification<t>* Compositespecification<t>::and (ispecification<t>* Other)
{
return new Andspecification<t> (this, other);
}
Template<class t>
ispecification<t>* Compositespecification<t>::or (ispecification<t>* Other)
{
return new Orspecification<t> (this, other);
}
Template<class t>
ispecification<t>* Compositespecification<t>::not ()
{
return new notspecification<t> (this);
}

Template<class t>
Andspecification<t>::andspecification (ispecification<t>* x, ispecification<t>* y)
{
M_one = x;
M_other = y;
}
Template<class t>
BOOL Andspecification<t>::issatisfiedby (int candidate)
{
Return M_one->issatisfiedby (Candidate) && M_other->issatisfiedby (candidate);
}

Template<class t>
Orspecification<t>::orspecification (ispecification<t>* x, ispecification<t>* y)
{
M_one = x;
M_other = y;
}

Template<class t>
BOOL Orspecification<t>::issatisfiedby (int candidate)
{
Return M_one->issatisfiedby (candidate) | | M_other->issatisfiedby (candidate);
}

Template<class t>
Notspecification<t>::notspecification (ispecification<t>* x)
{
m_wrapped = x;
}

Template<class t>
BOOL Notspecification<t>::issatisfiedby (int candidate)
{
Return!m_wrapped->issatisfiedby (candidate);
}

Test.cpp

#include "stdafx.h"
#include "Specification.h"

#include <vector>
#include <algorithm>
using namespace Std;

Class Oddspecification:public Compositespecification<int>
{
Public
virtual bool IsSatisfiedBy (int candidate)
{
Return candidate% 2! = 0;
}
};

Class Positivespecification:public Compositespecification<int>
{
Public
virtual bool IsSatisfiedBy (int candidate)
{
return candidate > 0;
}
};

int _tmain (int argc, _tchar* argv[])
{
Vector<int> Vint;
for (int i =-5; i <; i++)
Vint.push_back (i);

ispecification<int> *oddspec = new Oddspecification ();
ispecification<int> *positivespec = new Positivespecification ();
ispecification<int> *oddandpositivespec = Oddspec->and (Positivespec);

for (Vector<int>::iterator it = Vint.begin (); It! = Vint.end (); ++it)
{
if (Oddandpositivespec->issatisfiedby (*it))
if (Oddspec->issatisfiedby (*it))
printf ("%d\n", *it);

}

Delete Oddspec;
Delete Positivespec;
Delete Oddandpositivespec;
return 0;
}

Feeling fine, but run-time error, prompt:

>test.obj:error LNK2001: unresolved external symbol "Public:virtual class ispecification<int> * __thiscall compositespecificat Ion<int>::and (class ispecification<int> *) "([email protected][email protected]@@[email protected]@@[email protected]@z)
1>test.obj:error LNK2001: unresolved external symbol "Public:virtual class ispecification<int> * __thiscall Compositespecifica Tion<int>::or (class ispecification<int> *) "([email protected][email protected]@@[email protected]@@[email protected]@z)
1>test.obj:error LNK2001: unresolved external symbol "Public:virtual class ispecification<int> * __thiscall Compositespecifica Tion<int>::not (void) "([email protected][email protected]@@[email protected]@ @XZ)
1>d:\vsproject\pattern_sln\debug\specification.exe:fatal error Lnk1120:3 an unresolved external command

Don't want to understand, wait for the next solution.

Combined with the knowledge of the Internet, the specification mode is realized by C + +