C++ syntax, "MyClass m;" versus "MyClass m();"

[janzon]

Hi!

When defining a new object m of class MyClass, with no parameters to
the constructor, one is supposed to write "MyClass m;". If one wants to
pass a parameter p to the constructor, one is supposed to write
"MyClass m(p);". It doesn't work if one writes "MyClass m();" when one
wants to pass zero parameters. Why is that? It seems inelegant and
non-symmetric to me. What reason is there behind this?

/ Me, seeking insights into C++

[hit_pc]

On Fri, 19 Jan 2007 20:12:44 +0800, <ja****@gmail.comwrote:

"MyClass m(p);". It doesn't work if one writes "MyClass m();" when one
wants to pass zero parameters. Why is that? It seems inelegant and

if you write "MyClass m()",
it is not a Class,it is a function declare,
it means:this is a function ,its name is m,its param is void,and it
returns sth with type MyClass.
think about this:
you can declare a function like this:int func(int a)
also you can :int func(int)

--
Hello,World!
----legolaskiss.

[Rolf Magnus]

ja****@gmail.com wrote:

Hi!

When defining a new object m of class MyClass, with no parameters to
the constructor, one is supposed to write "MyClass m;". If one wants to
pass a parameter p to the constructor, one is supposed to write
"MyClass m(p);". It doesn't work if one writes "MyClass m();" when one
wants to pass zero parameters. Why is that? It seems inelegant and
non-symmetric to me. What reason is there behind this?

You're right in that it is kind of unintuitive. The reason is that
"MyClass m();" already has another meaning. It declares a function taking no
arguments and returnint MyClass, similar to "int myfunc();".

[Alex Vinokur]

Rolf Magnus wrote:

ja****@gmail.com wrote:

Hi!

When defining a new object m of class MyClass, with no parameters to
the constructor, one is supposed to write "MyClass m;". If one wants to
pass a parameter p to the constructor, one is supposed to write
"MyClass m(p);". It doesn't work if one writes "MyClass m();" when one
wants to pass zero parameters. Why is that? It seems inelegant and
non-symmetric to me. What reason is there behind this?

You're right in that it is kind of unintuitive. The reason is that
"MyClass m();" already has another meaning. It declares a function taking no
arguments and returnint MyClass, similar to "int myfunc();".

See a message related to the issue:
http://groups.google.com/group/comp....07f633d38f2f9f

Alex Vinokur
email: alex DOT vinokur AT gmail DOT com
http://mathforum.org/library/view/10978.html
http://sourceforge.net/users/alexvn