C++ constructor differs from java

[vinothg]

Hi,

I was just browsing some java code and found that it is possible in java to call a constructor within another constructor. The rule being that the it should be first line in the constructor and also there shouldn't be any duplication.Bot h these rules have valid reasons. But why can't we do the same in c++.

Java Code :

public class c {

public c(){}
public c(int a){
this();
}


C++ code :

class c{
public :
c(){}
c(int a){
this->c(); >>> Error
}
};

[vinothg]

Is it because "this" is a reference to the object in java and "this" is a pointer in c++

[JosAH]

Is it because "this" is a reference to the object in java and "this" is a pointer in c++

In both languages 'this' is a pointer to the object itself. Java doesn't even know
about references (although it (ab)uses the noun in several contexts). C++ has
initialization lists following the colon in the ctor header. Not as elegant as the
Java solution but doable; they're different languages you know.

kind regards,

Jos

[weaknessforcats]

this->c(); >>> Error

The this pointer can't be used to call a constructor inside the object constructor since this would set up an infinite recursion of calls.

You can, of cource call any constructor inside a constructor provided these calls are not on the same object:
[code=cpp]
class c
{
public :
c(){}
c(int a)
{
//this->c(); //>>> Error
c::c(); //OK. This is a different object
}
};
[/code]

Also, the function definition inisde the class is a Java thing. In C++ doing that makes the functions inline. Code your member functions outside the class.