C macro

[sunny]

Hi,
I have an intersting quesiton in my view. I have two write a
macro which tell what is the
type of argument being passed to it
i.e int, short, long, signed , unsigned..etc
like

typedef T unsigned int
value(T)

I have to printf() what kind of value T is...

Regards
Gurminder

[Richard Heathfield]

sunny said:

Hi,
I have an intersting quesiton in my view.

An interesting question? Cool.

I have two write a macro which tell what is the
type of argument being passed to it i.e int, short,
long, signed , unsigned..etc like

typedef T unsigned int
value(T)

I have to printf() what kind of value T is...

Okay, understood. Now, you said you had an interesting question, but I don't
see a question.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)

[Ancient_Hacker]

sunny wrote:

Hi,
I have an intersting quesiton in my view. I have two write a
macro which tell what is the
type of argument being passed to it
i.e int, short, long, signed , unsigned..etc
like

typedef T unsigned int
value(T)

I have to printf() what kind of value T is...

That's a bit of a challenge. Straight C doesnt have any type-inquiry
function at either compile-time or run-time, so just knowing the type
isnt of much help.

There is the rather barren sizeof() function, which will tell you how
many bytes T occupies, but that isnt very helpful, unless you assume
only integer-like types are going to be passed in. Even then it's
going to be a bit tricky to figure out if T is signed or unsigned.

Perhaps you could retell your question, in a bit more detail.

[Morris Dovey]

sunny (in 11************* *********@75g20 00...legro ups.com) said:

| Hi,
| I have an intersting quesiton in my view. I have two
| write a macro which tell what is the
| type of argument being passed to it
| i.e int, short, long, signed , unsigned..etc
| like
|
| typedef T unsigned int
| value(T)
|
| I have to printf() what kind of value T is...

An interesting assignment indeed. When is your solution due?

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto

[Tak-Shing Chan]

On Wed, 12 Jul 2006, sunny wrote:

Hi,
I have an intersting quesiton in my view. I have two write a
macro which tell what is the
type of argument being passed to it
i.e int, short, long, signed , unsigned..etc
like

typedef T unsigned int
value(T)

I have to printf() what kind of value T is...

Regards
Gurminder

If you want to do reflection in C you would need *much more*
than just a simple macro. At the very least, you would need to
create a struct wrapper containing a type field (enum) and a data
field (union of all data types used in your program). You would
then have to wrap all your "reflective " data with this struct.

Tak-Shing

[spibou]

sunny wrote:

Hi,
I have an intersting quesiton in my view. I have two write a
macro which tell what is the
type of argument being passed to it
i.e int, short, long, signed , unsigned..etc
like

typedef T unsigned int
value(T)

I have to printf() what kind of value T is...

I can think of a way to distinguish between signed and unsigned
but distinguishing between int and long I have no idea. I'll go
out on a limp and say that it can't be done.
Tak-Shing Chan wrote:

If you want to do reflection in C you would need *much more*
than just a simple macro. At the very least, you would need to
create a struct wrapper containing a type field (enum) and a data
field (union of all data types used in your program). You would
then have to wrap all your "reflective " data with this struct.

I have no idea what reflection means in this context.

[Clever Monkey]

sp****@gmail.co m wrote:

Tak-Shing Chan wrote:

> If you want to do reflection in C you would need *much more*
than just a simple macro. At the very least, you would need to
create a struct wrapper containing a type field (enum) and a data
field (union of all data types used in your program). You would
then have to wrap all your "reflective " data with this struct.

I have no idea what reflection means in this context.

Typical in OO languages is reflection:

"More generally, reflection is an activity in computation that allows an
object to have information about the structure and reason about its own
computation. The programming paradigm driven by reflection is called
reflective programming."

<http://en.wikipedia.or g/wiki/Reflection_%28c omputer_science %29>

Compare with introspection: The capability of some languages to
determine the type of objects at runtime.

<http://en.wikipedia.or g/wiki/Introspection_% 28computer_scie nce%29>

People are simulating reflection in C:
<http://www.google.com/search?hl=en&lr =&q=%22reflecti on+in+C%22>

[Walter Roberson]

In article <11************ *********@b28g2 000cwb.googlegr oups.com>,
<sp****@gmail.c omwrote:

>sunny wrote:

>I have to printf() what kind of value T is...

>I can think of a way to distinguish between signed and unsigned
but distinguishing between int and long I have no idea. I'll go
out on a limp and say that it can't be done.

if ( (unsigned T) ULONG_MAX == ULONG_MAX ) ...

Of course if int and long have the same range then it becomes
quite difficult to tell them apart ;-)
--
"It is important to remember that when it comes to law, computers
never make copies, only human beings make copies. Computers are given
commands, not permission. Only people can be given permission."
-- Brad Templeton

[Keith Thompson]

ro******@ibd.nr c-cnrc.gc.ca (Walter Roberson) writes:

In article <11************ *********@b28g2 000cwb.googlegr oups.com>,
<sp****@gmail.c omwrote:

>>sunny wrote:

>>I have to printf() what kind of value T is...

>>I can think of a way to distinguish between signed and unsigned
but distinguishing between int and long I have no idea. I'll go
out on a limp and say that it can't be done.

if ( (unsigned T) ULONG_MAX == ULONG_MAX ) ...

Of course if int and long have the same range then it becomes
quite difficult to tell them apart ;-)

You can tell them apart at the cost of a compilation failure. int and
long are compatible for most purposes, but int* and long* are not. If
you have a typedef T that could be either int or long, then of these
two expressions:
(T*)0 == (int*)0
(T*)0 == (long*)0
one will compile and one will not (more precisely one is a constraint
violation requiring a diagnostic).

This could be useful for some kind of pre-compilation configuration
system, but I can't think of any way to use it within a single legal
program.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Michael Mair]

Ancient_Hacker schrieb:
<snip>

There is the rather barren sizeof() function, which will tell you how

sizeof is an operator.
Example of use without parens:
....
p = malloc(number * sizeof *p);
....

Cheers
Michael
--
E-Mail: Mine is an /at/ gmx /dot/ de address.