What does this declarations means?

[shermaine80]

(a) int*p[3][3]
(b) int*(*p())[10];

(a) points to address of data in the row 3, column 3?
(b) can you advise me? thanks?

 

[Hurkyl]

Before I answer (a), do you know what

int a[3]

declares? What about

int a[3][3]



(b) means that some silly hacker likes to write obfuscated code, rather than use typedef's.

 

[shermaine80]

int a[3] is an array. It points to info at array[3]

 

[gunch]

(a) int*p[3][3]
int a[3] is an array. It points to info at array[3]

It doesn't just point to information at array[3] (what do you mean by that?), it actually contains 3 integers (in the programming sense).

T name[N]

Are arrays with N elements of type T.

T name[N1][N2];

Are arrays of N1 elements of arrays of N2 elements of type T.
In your first case we have a 3-dimensional array, where each element is another 3-dimensional array in which each element is a pointer to an integer.

It's often called a 3x3 multi-dimensional array, one example use would be:

int x,y,z;
int* a[3][3];
a[0][0] = &x; // Set the very first element of both arrays to point to x
a[0][2] = &y; // Let the last element of the first array point to y.
a[2][2] = &z; // Let the last element in both arrays point to z

As for the second, either someone misunderstood the syntax of function pointers or they are trying to confuse you.

int*(*p())[10];

Just like last time, this is an array, so p is an array of 10 int*(*())
The outer set of parentheses means nothing in this code, so it's equivalent to:

int** ();

Which is just a function returning a pointer to a pointer to an integer. So p is an array of functions, but we don't have first-class functions in C or C++, so we end up with an unusable array.

What was most likely meant if this is real code is:

int*(*p)()[10];

Which is an array of 10 functions pointers, each pointing to a function returning a pointer to an integer and taking no arguments.

 

[Hurkyl]

Just like last time, this is an array, so p is an array of 10 int*(*())

Almost: p is function that returns an int*[10].

Also,

int*(*p)()[10];

doesn't quite work: gcc complains with

`p' declared as function returning an array

You're looking for

int*(*p[10])();