inheritance

ema897 (80)
given:
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   class Component {
public:
    Component();
    virtual ~Component();
    void logicFunction();
    void setInputs( Component &);
    char getOutput() const;
    Component* leftChild();
    Component* rightChild();
    //void setState(bool&);//serve per vettore input: essendo vettore component, serve il metodo che viene implementato in constant component
protected:
    char  _present_state,_previous_state;
    Component *_x1,*_x2;
    float _lh,_hl;// consumo da low a high e da high a low
private:
};

class And : public Component{
public:
    And();
    virtual ~And();
    void logicFunction();
    void setInputs( Component&,  Component&);
protected:

private:
    //Component *_x2;
} ;

char toChar(bool x){
    char c;
    if(x) c='1';
    else c='0';
    return c;
}

bool toBool(char c){
    bool x;
    if (c='1') x=true;
    else x=false;
    return x;
}

Component ::Component() {
    //ctor
}

Component ::~Component() {
    //dtor
}

void Component :: logicFunction() {}
void Component ::setInputs( Component &a){
    _x1=&a;
}

char Component ::getOutput() const {
    return _present_state;
}

Component* Component :: leftChild(){
    return _x1;
}
Component* Component :: rightChild(){
    return _x2;
}

And ::And(){
    _x1= nullptr;
    _x2= nullptr;
}

And :: ~And() {
    //dtor
}

void And::logicFunction() {
    _previous_state=_present_state;
    if((_x1->getOutput()=='x')||(_x2->getOutput()=='x')) _present_state='x';
    else _present_state=toChar(toBool(_x1->getOutput())&&toBool(_x2->getOutput()));
}

void And::setInputs( Component &a,  Component &b) {
    _x1=&a;
    _x2=&b;
}


if I try:
Last edited on
ema897 (80)
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 postOrder(Component* node) {
    if(node== nullptr) return;
    postOrder(node->leftChild());
    postOrder(node->rightChild());
    node->logicFunction();
}

If I have a And object, when I try to do node->logicFunction(), I think it's executed Component::logicFunction() instead of And::logicFunction()..
why this?
dutch (2548)
Have you heard of virtual functions? If not, look it up.
You need to make logicFunction virtual in Component.

 
 
    virtual void logicFunction();

ema897 (80)
Yes I tried, but if do:

 
 
    virtual void logicFunction();

I receive error: undefined reference to `Component::logicFunction()'

instead with: 
 
 
    virtual void logicFunction()=0;

It doesn't work..
dutch (2548)
I don't understand the problem.

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#include <iostream>

class Component {
public:
    Component();
    virtual ~Component();
    virtual void logicFunction();
};

Component::Component() {}
Component::~Component() {}
void Component::logicFunction() { std::cout << "Component\n"; }

class And : public Component {
public:
    And();
    ~And();
    void logicFunction() override;
};

And::And() {}
And::~And() {}
void And::logicFunction() { std::cout << "And\n"; }

int main() {
    Component *comp = new And;
    comp->logicFunction();  // prints "And"
}

Last edited on
ema897 (80)
done. Thank you very much.
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