function is not an object

[asdf]

True or false ?

[Phlip]

asdf wrote:

True or false ?

Objects have state, identity, lifespan, storage, and behavior. Which of
those do functions have? Can you point to a function?

--
Phlip
http://www.greencheese.us/ZeekLand <-- NOT a blog!!!

[asdf]

So function is not an object.

But I think I can point to a function, by the pointer to the function.

Phlip wrote:

asdf wrote:

True or false ?

Objects have state, identity, lifespan, storage, and behavior. Which of
those do functions have? Can you point to a function?

--
Phlip
http://www.greencheese.us/ZeekLand <-- NOT a blog!!!

[pauldepstein]

asdf wrote:

True or false ?

This question seems to be about how the c++ community defines the
"object" concept.

I would say "false". Here's why.

The * symbol is used for dereferencing or defining a pointer to an
object.

However, the * symbol is also used to define a pointer to a function.

So, if a function is not an object, what is the type-of-thing that a
pointer to a function points to?

I would say that a pointer-to-a-function is an example of a
pointer-to-an-object, and hence a function is an object.

Paul Epstein

[Kai-Uwe Bux]

asdf wrote:

True or false ?

From the standard [1.8/1]

The constructs in a C++ program create, destroy, refer to, access, and
manipulate objects. An object is a region of storage. [Note: A function is
not an object, regardless of whether or not it occupies storage in the way
that objects do.]
Best

Kai-Uwe Bux

[Daniel T.]

"asdf" <li*********@gm ail.comwrote:

True or false ?

From the book C++ FAQs 2nd ed.

FAQ 5.06: What is an object? It depends on who you are. To a
programmer, an object is a region of storage with associated
semantics. To a designer, an object is any identifiable component in
the problem domain.

FAQ 5.08: A class can be thought of as a C=style function that can
maintain state between invocations in a thread-safe manner and can
also provide multiple services. If there wer exactly one instance of
a class, and all its member functions except for exactly one public:
member function were removed, the result would be a C-style function
(the object's data would correspond to static data that is local to
the function.)

--
There are two things that simply cannot be doubted. Logic and our
ability to sense the world around us. Doubt those, and you no longer
have anyone to discuss it with, nor any ability to discuss it.

[Phlip]

>Objects have state, identity, lifespan, storage, and behavior. Which of

>those do functions have? Can you point to a function?

asdf top-posted:

So function is not an object.

Read what I wrote. I think functions have all of those. Except you can't
create them with 'new', so their lifetime options are kind'a limit.

Daniel T. wrote:

From the book C++ FAQs 2nd ed.

FAQ 5.06: What is an object? It depends on who you are. To a
programmer, an object is a region of storage with associated
semantics. To a designer, an object is any identifiable component in
the problem domain.

FAQ 5.08: A class can be thought of as a C=style function that can
maintain state between invocations in a thread-safe manner and can
also provide multiple services. If there wer exactly one instance of
a class, and all its member functions except for exactly one public:
member function were removed, the result would be a C-style function
(the object's data would correspond to static data that is local to
the function.)

However, the book Design Patterns sez to create the Flyweight Design
Pattern, you create a table of objects, each with no state.

Now if I felt like implementing that pattern using a table of function
pointers, then do I don't have a "reeeeeal" Flyweight Design Pattern??

Or is the Standard's answer to the question "are functions objects?" not
always absolute and perfectly useful?

--
Phlip
http://www.greencheese.us/ZeekLand <-- NOT a blog!!!

[Daniel T.]

"Phlip" <ph******@yahoo .comwrote:

>>Objects have state, identity, lifespan, storage, and behavior.
Which of those do functions have? Can you point to a function?

asdf top-posted:

>So function is not an object.

Read what I wrote. I think functions have all of those. Except you
can't create them with 'new', so their lifetime options are kind'a
limit.

How does a function have state? More spicifically how does it have more
than one state?

Daniel T. wrote:

>From the book C++ FAQs 2nd ed.

FAQ 5.06: What is an object? It depends on who you are. To a
programmer, an object is a region of storage with associated
semantics. To a designer, an object is any identifiable component
in the problem domain.

FAQ 5.08: A class can be thought of as a C=style function that
can maintain state between invocations in a thread-safe manner
and can also provide multiple services. If there wer exactly one
instance of a class, and all its member functions except for
exactly one public: member function were removed, the result
would be a C-style function (the object's data would correspond
to static data that is local to the function.)

However, the book Design Patterns sez to create the Flyweight Design
Pattern, you create a table of objects, each with no state.

By your own definition above (and Grady Booch's BTW) an "object" with no
state, isn't an object.

Now if I felt like implementing that pattern using a table of
function pointers, then do I don't have a "reeeeeal" Flyweight
Design Pattern??

Of course, but are the stateless things used by the pattern objects?

Or is the Standard's answer to the question "are functions objects?"
not always absolute and perfectly useful?

I don't think anyone would argue that only objects can be useful. Is the
definition useful? I think so, one needs to treat a state-full thing
differently than a stateless thing. An object different than a
non-object.

This doesn't really sound like it belongs in comp.lang.c++ though.

--
There are two things that simply cannot be doubted. Logic and our
ability to sense the world around us. Doubt those, and you no longer
have anyone to discuss it with, nor any ability to discuss it.

[Phlip]

Daniel T. wrote:

How does a function have state? More spicifically how does it have more
than one state?

Well, it can only have one instance...

....so nobody said it had to have more state than instance... ;-)

>However, the book Design Patterns sez to create the Flyweight Design
Pattern, you create a table of objects, each with no state.

By your own definition above (and Grady Booch's BTW) an "object" with no
state, isn't an object.

I don't care what authority said what objects are objects - including
myself. If I want to call functions used as objects in the Flyweight Pattern
"objects", then they are. What's most important is the term is useful, not
that it's more exact or more authoritative.

>Now if I felt like implementing that pattern using a table of
function pointers, then do I don't have a "reeeeeal" Flyweight
Design Pattern??

Of course, but are the stateless things used by the pattern objects?

Uh, I think they are implemented as instances of classes. So maybe they
aren't!

>Or is the Standard's answer to the question "are functions objects?"
not always absolute and perfectly useful?

I don't think anyone would argue that only objects can be useful.

I didn't say that.

Is the
definition useful? I think so, one needs to treat a state-full thing
differently than a stateless thing. An object different than a
non-object.

How about we relax and write good OO designs.

--
Phlip
http://www.greencheese.us/ZeekLand <-- NOT a blog!!!

[Jerry Coffin]

In article <da************ *************** *@news.west.ear thlink.net>,
da******@earthl ink.net says...

[ ... ]

How does a function have state? More spicifically how does it have more
than one state?

Usually by using a static variable. For example:

enum dir { in, out };

int rand(enum dir direction, int var = 0) {

static int seed;

if (direction == in) {
seed = *var;
return 0;
}
else {
seed *= 31415927;
++seed;
return seed;
}
}

A function can have as much state data and as many states as it wishes
(within the storag limits of the implementation, of course).

I'd also note that this is somewhat language-specific. Quite a few
languages don't support a function with state like C++ does. Some
attempt to define functions so they fit closely with the usual
mathematical definition, where the output depends only on the input.
Others allow some sort of state, but with substantial limitations, and
still others more or less arbitrary state.

--
Later,
Jerry.

The universe is a figment of its own imagination.