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Top Forums Programming Pointer for 2D array seems to be 3D in C Post 302999280 by Corona688 on Friday 16th of June 2017 11:13:22 AM
Old 06-16-2017
1) They probably differ in being constants or non-constants.

3) It's "3d" because you have an extra pointer in the way. Every level of pointers requires another dereferencing operation to access it. One level pointer requires one. Two level pointer requires two. Three level pointer requires three. 97 level pointer requires 97. That is the pattern.

The first dereferencing operation gets rid of is x itself; once you do so, you are essentially accessing y. The next level of pointers points to individual rows inside y. The last level gets you an individual cell in that row.

Code:
x; // pointer to Y
(*x); // Y, i.e. pointer to rows
(*x)[0]; // Pointer to row 0
(*x)[0][0] // Row 0 col 0.  No longer a pointer.

The diagram is x -> y -> row -> column.
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SCANDIR(3)						     Library Functions Manual							SCANDIR(3)

NAME
scandir, alphasort - scan a directory SYNOPSIS
#include <sys/types.h> #include <sys/dir.h> scandir(dirname, namelist, select, compar) char *dirname; struct direct *(*namelist[]); int (*select)(); int (*compar)(); alphasort(d1, d2) struct direct **d1, **d2; DESCRIPTION
Scandir reads the directory dirname and builds an array of pointers to directory entries using malloc(3). It returns the number of entries in the array and a pointer to the array through namelist. The select parameter is a pointer to a user supplied subroutine which is called by scandir to select which entries are to be included in the array. The select routine is passed a pointer to a directory entry and should return a non-zero value if the directory entry is to be included in the array. If select is null, then all the directory entries will be included. The compar parameter is a pointer to a user supplied subroutine which is passed to qsort(3) to sort the completed array. If this pointer is null, the array is not sorted. Alphasort is a routine which can be used for the compar parameter to sort the array alphabetically. The memory allocated for the array can be deallocated with free (see malloc(3)) by freeing each pointer in the array and the array itself. SEE ALSO
directory(3), malloc(3), qsort(3), dir(5) DIAGNOSTICS
Returns -1 if the directory cannot be opened for reading or if malloc(3) cannot allocate enough memory to hold all the data structures. 4.2 Berkeley Distribution September 17, 1985 SCANDIR(3)
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