Studying operator overloading
I'm studying operator overloading and can not understand how that is identified using the + + operator pre-set or post-set.
------ CODE --------------------------------------------------
#include <iostream>
using namespace std;
class ponto
{private:
int x,y;
public:
ponto(int x1=0, int y1=0) {x=x1;y=y1;} // Constructor
ponto operator ++() //Function operator PRE-FIXED
{
++x;++y;
return ponto(x,y);
}
ponto operator ++(int) //Function operator POS-FIXED
{
++x;++y;
return ponto(x-1,y-1);
}
void printpt() const
{
cout <<'('<< x <<','<<y<<')';
}
};
void main()
{ponto p1,p2(2,3),p3;
cout << "\n p1 = "; p1.printpt();
cout << "\n p2 = "; p2.printpt();
cout << "\n++p1 = ";
(++p1).printpt(); //increases after use
cout << "\np2++ = ";
(p2++).printpt(); //uses after incrases
cout << "\n p2 = "; p2.printpt();
p3 = p1++; //assigns after increases
cout << "\n p3 = "; p3.printpt();
cout << "\n p1 = "; p1.printpt();
}
Re: Studying operator overloading
Quote:
Originally Posted by
Alex_Brazil
I'm studying operator overloading and can not understand how that is identified using the + + operator pre-set or post-set.
First, use proper code tags when posting code. There is no need for "Indent" tags if you just posted using code tags:
[code]
Your code goes here
[/code]
Example:
Code:
#include <iostream>
int main()
{
std::cout << "Hello World";
}
See how the code looks when I post as compared to when you post code?
Second, if you're studying operator overloading, why are you using such a confusing and wrong piece of code to study this? Please see the FAQ on overloading ++ here, and compare the simple example and explanation of this operator and how it is to be overloaded to what you're doing.
http://www.parashift.com/c++-faq/inc...erloading.html
The first glaring issue is that the prefix ++ should be returning a reference to the current object, and your code doesn't do that.
Regards,
Paul McKenzie
Re: Studying operator overloading
I am grateful for the support I have received from members of this forum and apologize for the mistakes of posting, no formatting required.
I created a new code to study the overhead of a binary operator, where the operator +, but the compiler returns the following error: "main.obj: -1: error: LNK2019: unresolved external symbol" public: __ thiscall sale sale :: (void) "(? 0venda @ @ QAE @ XZ) referenced in function _main".
I do not understand what is generating the error. Can anyone help me?
Follow the code:
Code:
#include <iostream>
#include <iomanip>
using namespace std;
class venda
{
private:
int npecas;
float precos;
public:
venda();
venda(int np, float p) {npecas = np;precos = p;}
venda operator + (venda v) const;
void getvenda()
{
cout << "\nInsira o nr de pecas: "; cin >> npecas;
cout << "\nInsira o preco: "; cin >> precos;
}
void printvenda() const;
};
//int venda::npecas;
//float venda::precos;
venda venda::operator +(venda v) const
{
int pec = npecas + v.npecas;
float pre = precos + v.precos;
return venda(pec,pre);
}
void venda::printvenda() const
{
cout << setiosflags(ios::fixed)
<< setiosflags(ios::showpoint)
<< setprecision(2)
<< setw(10) <<npecas;
cout << setw(10) << precos << '\n';
}
void main()
{
venda A(58,34.53), B, C(30,60.3), T, Total;
B.getvenda();
T = A + B;
Total= A + B + C;
cout << "Venda: A .............."; A.printvenda();
cout << "Venda: B .............."; B.printvenda();
cout << "Venda: A + B .........."; T.printvenda();
cout << "Venda: Totais A+B+C...."; Total.printvenda();
}
Re: Studying operator overloading
This line.
venda();
You declared a constructor but didn't give it a body.
Re: Studying operator overloading
Thank you. The problem was solved.
Re: Studying operator overloading
Operator Overloading - object returns wrong value
Another example I created for my study, but the objects s3, s4 and s5 are returning wrong values. Someone knows you explain why?
Code:
#include <iostream>
#include <string>
const int MAX = 80;
using namespace std;
class string2
{
private:
char str[MAX];
public:
string2() {str[0]='\0';}
string2(char s[]) {strcpy(str,s);}
string2 operator +=(string2 s) const //Concatena
{
string2 temp;
if(strlen(str)+strlen(s.str) < MAX)
{
strcpy(temp.str,str);
strcat(temp.str,s.str);
}
else
cout << "\nMemor;ia Cheia!";
return temp;
}
string2 operator +(string2 s) const // Concatena
{
string2 temp;
temp +=s.str;
return temp;
}
void print() const {cout << str;}
};
int main()
{
string2 s1("Feliz Aniversario! "),
s2("Denise."),
s3("Bom Dia! "), s4, s5;
cout << "\ns1 = "; s1.print();
cout << "\ns2 = "; s2.print();
s3 += s2;
s4 = s1 + s2;
s5 = s1 + s1;
cout << "\ns3 = "; s3.print();
cout << "\ns4 = "; s4.print();
cout << "\ns5 = "; s5.print();
}
Re: Studying operator overloading
Quote:
Originally Posted by
Alex_Brazil
Operator Overloading - object returns wrong value
Another example I created for my study,
You need to study a bit more before creating your own examples:
Code:
string2 operator +=(string2 s) const //Concatena
Why are you passing string2 objects by value? You should be passing them by const reference, not by value.
Code:
string2 operator +=(string2 s) const //Concatena
Why is operator += returning a new object? It should be returning a reference to the existing object. That is the whole purpose of +=. It takes the existing object, adds something to it, and returns the existing object.
Everything I pointed out is covered in good books. Are you learning from real books? If you're just throwing things together without any guidance, that is not the way you learn C++. You're supposed to be using good books (and tutorials) on the language, i.e. see how the experts in the language do things. Putting stuff together yourself just leads to mistakes and a misunderstanding of how to use C++ properly.
Regards,
Paul McKenzie
