By using this site, you agree to our updated Privacy Policy and our Terms of Use. Manage your Cookies Settings.
455,426 Members | 1,757 Online
Bytes IT Community
+ Ask a Question
Need help? Post your question and get tips & solutions from a community of 455,426 IT Pros & Developers. It's quick & easy.

What is function pointer?

P: n/a
hi friend,

what is function pointer how it is useful?
plz help me.

Nov 15 '05 #1
Share this Question
Share on Google+
10 Replies


P: n/a
sabarish wrote:
what is function pointer how it is useful?


Search the web. A Google search for 'C "function pointer"' gives instant
results.

S.
Nov 15 '05 #2

P: n/a
"sabarish" <su******@gmail.com> wrote in message
news:11**********************@z14g2000cwz.googlegr oups.com...
hi friend,

what is function pointer
A pointer object or value which contains the address
of a function.
how it is useful?


If one doesn't know what it is, not at all.

Now a question for you:
"What is a textbook, and how is it useful?"

-Mike
Nov 15 '05 #3

P: n/a
"sabarish" writes:
what is function pointer how it is useful?


It is a pointer that points to a function rather to a variable which is the
more common case.

A nice understandable usage is in the standard library, qsort which is geek
speak for quick sort. Think of three functions, main, qsort and compare.
main contains a pointer to compare which will tell qsort *how* to compare.
Comparing doubles is different that comparing ints, for example. so main
calls qsort and passes the pointer to compare (a function pointer) in the
argument list. This means that qsort can, in turn, use (call) the proper
compare function.
Nov 15 '05 #4

P: n/a
sabarish wrote:

hi friend,

what is function pointer how it is useful?
plz help me.


The only thing that you can do with the name of a function
in a correct C program, is derive a pointer from it,
either through the address operator &, or by conversion.

--
pete
Nov 15 '05 #5

P: n/a

"pete" <pf*****@mindspring.com> wrote in message
news:43***********@mindspring.com...
sabarish wrote:

hi friend,

what is function pointer how it is useful?
plz help me.


The only thing that you can do with the name of a function
in a correct C program, is derive a pointer from it,
either through the address operator &, or by conversion.


The *only* thing?

What about calling the function? :-)

-Mike
Nov 15 '05 #6

P: n/a
sabarish wrote:
hi friend,

what is function pointer how it is useful?
plz help me.


I suggest you just post the complete assignment together with your
instructors email address so we can send the answers direct.

Alternatively, at least attempt to find the answers in your text book.
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.
Nov 15 '05 #7

P: n/a
"osmium" <r1********@comcast.net> writes:
"sabarish" writes:
what is function pointer how it is useful?


It is a pointer that points to a function rather to a variable which is the
more common case.

A nice understandable usage is in the standard library, qsort which is geek
speak for quick sort.

[snip]

Going off on a tangent ...

Quicksort is a specific recursive sorting algorithm. The name "qsort"
probably was originally an abbreviation for "quicksort" (back in the
days when some systems had severe limits on the lengths of external
names), but there's no implication in the standard that it uses any
particular algorithm.

--
Keith Thompson (The_Other_Keith) 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.
Nov 15 '05 #8

P: n/a
"Mike Wahler" <mk******@mkwahler.net> writes:
"pete" <pf*****@mindspring.com> wrote in message
news:43***********@mindspring.com...
sabarish wrote:

hi friend,

what is function pointer how it is useful?
plz help me.


The only thing that you can do with the name of a function
in a correct C program, is derive a pointer from it,
either through the address operator &, or by conversion.


The *only* thing?

What about calling the function? :-)


All function calls take place via function pointers. See the
standard:

6.5.2.2 Function calls
Constraints
1 The expression that denotes the called function77) shall have
type pointer to function returning void or returning an
object type other than an array type.

....

77) Most often, this is the result of converting an
identifier that is a function designator.

--
"For those who want to translate C to Pascal, it may be that a lobotomy
serves your needs better." --M. Ambuhl

"Here are the steps to create a C-to-Turbo-Pascal translator..." --H. Schildt
Nov 15 '05 #9

P: n/a
"Mike Wahler" <mk******@mkwahler.net> writes:
"pete" <pf*****@mindspring.com> wrote in message
news:43***********@mindspring.com...
sabarish wrote:

hi friend,

what is function pointer how it is useful?
plz help me.


The only thing that you can do with the name of a function
in a correct C program, is derive a pointer from it,
either through the address operator &, or by conversion.


The *only* thing?

What about calling the function? :-)


The function call operator requires a function pointer. Given a
function name, you can't call the function without converting it to a
pointer, usually implicitly.

--
Keith Thompson (The_Other_Keith) 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.
Nov 15 '05 #10

P: n/a
"Ben Pfaff" <bl*@cs.stanford.edu> wrote in message
news:87************@benpfaff.org...
"Mike Wahler" <mk******@mkwahler.net> writes:
"pete" <pf*****@mindspring.com> wrote in message
news:43***********@mindspring.com...
The only thing that you can do with the name of a function
in a correct C program, is derive a pointer from it,
either through the address operator &, or by conversion.


The *only* thing?

What about calling the function? :-)


All function calls take place via function pointers. See the
standard:

6.5.2.2 Function calls
Constraints
1 The expression that denotes the called function77) shall have
type pointer to function returning void or returning an
object type other than an array type.

...

77) Most often, this is the result of converting an
identifier that is a function designator.


I stand educated. Thanks.

-Mike
Nov 15 '05 #11

This discussion thread is closed

Replies have been disabled for this discussion.