C + + operator Knowledge Point 2

http://blog.csdn.net/szlanny/article/details/4295854

Operator it has two usages, one is operator overloading (operator overloading), and the other is operator casting (operation implicit conversion).

1.operator overloading
C + + can be overloaded with operator operators, in the following format: type T operator operator (), such as gravity Load +, as shown below

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1. template<TypeName t> class A
2. {
3. Public
4. Const T operator + (const t& RHS)
5. {
6. return this->m_ + RHS;
7. }
8. Private
9. T m_;
10. };

Another example is the function object in STL, overloaded (), which is the more recommended notation in C + +, similar to function pointers, as shown below

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1. Template<typename t> struct A
2. {
3. T operator () (const t& LHS, const t& RHS) { return LHS-RHS;}
4. };

2 operator Casting
C + + can be operator overloaded with implicit conversions in the following format: operator type T (), as shown below

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2. Class A
4. {
6. Public
8. Operator b* () { return this->b_;}
10. operator Const b* () const {return this->b_;}
12. Operator b& () { return *this->b_;}
14. operator Const b& () const {return *this->b_;}
18. Private
20. b* b_;
22. };

A;
When the if (a), compile, where it is converted to if (A.operator b* ()), in fact is to judge if (A.b_)

I have a close-up of 2 examples of these two usages.

Class Test//Overloaded classes
{
Public
Test (int a)
{
M_age = A;
}
~test () {}

Test operator = (test &temp)
{
This->m_age = Temp.m_age;

return *this;
}

Test operator + = (Test & TEMP2)
{
This->m_age + = Temp2.m_age;

return *this;
}

Public
int m_age;

};

Class TESTB//Implicit conversion
{
Public
Testb () {}
~testb () {}

char* Getstr ()
{
memset (m_buf, 0, 30);
strcpy (M_BUF, "Get Str ()");
printf ("Get str () \ n");

return m_buf;
}

Operator char* ()
{
memset (m_buf, 0, 30);
strcpy (M_BUF, "char *");
printf ("Char *\n");

return m_buf;
}

Public
Char m_buf[30];

};

int main ()
{
Test A (5), B (15);

A = b;
printf ("a.m_age=%d\n", a.m_age);//15

A + = B;
printf ("a.m_age=%d\n", a.m_age);//30

TESTB BB;
char *ptest1 = BB; printf char * Here TESTB is converted to char *
Char *ptest2 = BB.GETSTR (); printf Get str ()

return 0;

}

C + + operator Knowledge Point 2