S
sabarish
hi friend,
what is function pointer how it is useful?
plz help me.
what is function pointer how it is useful?
plz help me.
S
Skarmander
sabarish said:
Search the web. A Google search for 'C "function pointer"' gives instant
results.
S.
M
Mike Wahler
sabarish said:
A pointer object or value which contains the address
of a function.
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
F
Flash Gordon
sabarish said:
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.
O
osmium
sabarish said:
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.
P
pete
sabarish said:
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.
M
Mike Wahler
pete said:
The *only* thing?
What about calling the function?
-Mike
B
Ben Pfaff
Mike Wahler said: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.
K
Keith Thompson
[snip]osmium said:
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.
K
Keith Thompson
Mike Wahler said: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.
M
Mike Wahler
Ben Pfaff said:
I stand educated. Thanks.
-Mike