c++，冰.虚拟功能是纯粹的内部功能

我只是想从zeroc（带打印机的那个）修改一下这个例子。事情是这样的。

以下是Pritner.ice文件中的小界面：

#pragma once
module Demo
{
    interface Printer
    {
    void printString(string s);
    void printFloat(float val);
    };
};

以及服务器端产生错误的类。

#include <Ice/Ice.h>
#include <Printer.h>
using namespace std;
using namespace Demo;
class PrinterI : public Printer
{
public:
   virtual void printString(const string &, const Ice::Current&);
    virtual void printFloat(const float &, const Ice::Current&);    
};

void 
PrinterI::
printFloat(const float &val,const Ice::Current&)
{
    cout<<val<<endl;
}
void 
PrinterI::
printString(const string &s, const Ice::Current&)
{
    cout << s << endl;
}

错误如下：

Server.cpp: In function ‘int main(int, char**)’:
Server.cpp:49:37: error: cannot allocate an object of abstract type ‘PrinterI’
         Ice::ObjectPtr object = new PrinterI;
                                     ^
Server.cpp:16:7: note:   because the following virtual functions are pure within ‘PrinterI’:
 class PrinterI : public Printer
       ^
In file included from Server.cpp:11:0:
./Printer.h:430:18: note:   virtual void Demo::Printer::printFloat(Ice::Float, const Ice::Current&)
     virtual void printFloat(::Ice::Float, const ::Ice::Current& = ::Ice::Current()) = 0;
                  ^
make: *** [Server.o] Error 1

主要代码：

int
main(int argc, char* argv[]){
int status = 0;
Ice::CommunicatorPtr ic;
try
{
    ic = Ice::initialize(argc, argv);
    Ice::ObjectAdapterPtr adapter =
        ic->createObjectAdapterWithEndpoints("SimplePrinterAdapter", "default -h localhost -p 10000");
    Ice::ObjectPtr object = new PrinterI;
    adapter->add(object, ic->stringToIdentity("SimplePrinter"));
    adapter->activate();
    ic->waitForShutdown();
}
catch(const Ice::Exception& e)
{
    cerr << e << endl;
    status = 1;
}
catch(const char* msg)
{
    cerr << msg << endl;
    status = 1;
}
if(ic)
{
    try
    {
        ic->destroy();
    }
    catch(const Ice::Exception& e)
    {
        cerr << e << endl;
        status = 1;
    }
}
return status;
}

printString的部分很好，工作得很好，但当我想在interface的函数中使用float作为参数时，就会产生错误。我承认我不是c++专家，但我已经没有任何关于如何解决这个问题的线索了。