Programming Forums > Application Development > C++

biohazard · Apr 23rd, 2006, 9:54 AM

I wrote the following program:

#include<iostream>
using namespace std;
class add
{
public:
add();
add(int,int);
};
int add::add()
{
cout<<"Constructor"<<endl;
}
int add::add(int x,int y)
{
cout<<"The sum of the two no.s is"<<x+y<<endl;
}
int main()
{
add a;
a.add();
a.add(5,6);
return 0;
}

The compiler is saying that I am not using the correct return type for the constructors.

t.i.g.e.r · Apr 23rd, 2006, 10:01 AM

use add::add() instead of int add::add()

biohazard · Apr 23rd, 2006, 10:03 AM

Are you sure? Functions should have a rreturn type specified.

Ooble · Apr 23rd, 2006, 10:05 AM

Constructors and deconstructors, by definition, cannot return anything. You're therefore not allowed to have a return type. Not even void.

biohazard · Apr 23rd, 2006, 10:10 AM

Okay. If I remove the return types, the program will work fine?

t.i.g.e.r · Apr 23rd, 2006, 10:17 AM

yeah, cons. and dest. w/out return types

InfoGeek · Apr 23rd, 2006, 10:20 AM

Yeah, It should. The constructor doesn't return anything via the return statement. It implicitely returns the class object.

grumpy · Apr 23rd, 2006, 11:08 AM

Quote:

Originally Posted by InfoGeek

Yeah, It should. The constructor doesn't return anything via the return statement. It implicitely returns the class object.

Your first comment is correct, your second is not; constructors do not return anything. As Ooble said, no return type is allowed to be specified.

A constructor initialises an object; it does not return it.

The process of constructing an object goes in two phases: first, raw memory is found that will be used to represent the object. Second, an appropriate constructor is invoked to turn that raw memory into an actual object. The process of destroying an object works in reverse: a destructor is invoked to turn the object back to raw memory, and then the memory is released (as far as the program is concerned).

java_roshan · Apr 23rd, 2006, 11:16 AM

<snip>

Quote:

Originally Posted by grumpy

The process of constructing an object goes in two phases: first, raw memory is found that will be used to represent the object. Second, an appropriate constructor is invoked to turn that raw memory into an actual object.

Could you please elaborate on Raw Memory?

DaWei · Apr 23rd, 2006, 11:42 AM

Memory to hold an instantiated object. The class definition is just a spec, a blueprint. When you instantiate, actual memory must be used. This may be local or dynamically allocated, for instance, depending upon the statement you write to instantiate. The appropriate amount of memory, once acquired, is just a block of junk. Construction of the object, and any initialization, take care of making it useful.

Apr 23rd, 2006, 9:54 AM	#1
biohazard Newbie Join Date: Feb 2006 Posts: 18 Rep Power: 0	Constructor problem I wrote the following program: (Toggle Plain Text) #include<iostream> using namespace std; class add { public: add(); add(int,int); }; int add::add() { cout<<"Constructor"<<endl; } int add::add(int x,int y) { cout<<"The sum of the two no.s is"<<x+y<<endl; } int main() { add a; a.add(); a.add(5,6); return 0; } #include<iostream> using namespace std; class add { public: add(); add(int,int); }; int add::add() { cout<<"Constructor"<<endl; } int add::add(int x,int y) { cout<<"The sum of the two no.s is"<<x+y<<endl; } int main() { add a; a.add(); a.add(5,6); return 0; } The compiler is saying that I am not using the correct return type for the constructors. __________________ Let us be thankful for the fools. But for them the rest of us could not succeed<Mark Twain> Get your facts first, and then you can distort them as much as you please<Mark Twain>

Apr 23rd, 2006, 10:03 AM	#3
biohazard Newbie Join Date: Feb 2006 Posts: 18 Rep Power: 0	Are you sure? Functions should have a rreturn type specified. __________________ Let us be thankful for the fools. But for them the rest of us could not succeed<Mark Twain> Get your facts first, and then you can distort them as much as you please<Mark Twain>

Apr 23rd, 2006, 10:05 AM	#4
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Constructors and deconstructors, by definition, cannot return anything. You're therefore not allowed to have a return type. Not even void. __________________ Me :: You :: Them

Apr 23rd, 2006, 10:10 AM	#5
biohazard Newbie Join Date: Feb 2006 Posts: 18 Rep Power: 0	Okay. If I remove the return types, the program will work fine? __________________ Let us be thankful for the fools. But for them the rest of us could not succeed<Mark Twain> Get your facts first, and then you can distort them as much as you please<Mark Twain>

Apr 23rd, 2006, 10:20 AM	#7
InfoGeek Professional Programmer Join Date: Jun 2005 Location: India, The great. Posts: 435 Rep Power: 4	Yeah, It should. The constructor doesn't return anything via the return statement. It implicitely returns the class object. __________________ PFO - My daily dose of technology.

Apr 23rd, 2006, 10:01 AM	#2
t.i.g.e.r Newbie Join Date: Apr 2006 Location: CZ-brno Posts: 7 Rep Power: 0	use add::add() instead of int add::add()

Apr 23rd, 2006, 10:17 AM	#6
t.i.g.e.r Newbie Join Date: Apr 2006 Location: CZ-brno Posts: 7 Rep Power: 0	yeah, cons. and dest. w/out return types

Apr 23rd, 2006, 11:42 AM	#10
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Memory to hold an instantiated object. The class definition is just a spec, a blueprint. When you instantiate, actual memory must be used. This may be local or dynamically allocated, for instance, depending upon the statement you write to instantiate. The appropriate amount of memory, once acquired, is just a block of junk. Construction of the object, and any initialization, take care of making it useful. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Programming Forums > Application Development > C++

Constructor problem