The array is automatically converted to the same type of pointer __ function as a function parameter

High-quality C + + programming guidelines indicate that when an array is passed as a function parameter, the array is automatically degraded to the same type of pointer, which is correct for a one-dimensional array (currently considered correct), but for multidimensional arrays, this is clearly not exactly true. The C language takes an array parameter as a pointer because of efficiency, and if you copy an array all this is a loss of performance. So at the moment, whether you write in a function declaration like ' void Func1 (char a[]) ', or like ' void Func1 (char *a) ', the compiler will look at it as the latter form.
So for a regular examination of the written questions:
Void f (Char a[])
{
Cout<<sizeof (a) <<endl;
}
The output is naturally 4. (The default pointer occupies 4 digits, followed by this standard)
For two-dimensional array situations, two-dimensional arrays can be represented in several forms:
(1) Char A[m][n]--standard form;
(2) Char *p[n]--pointer array form;
(3) char (*P) [n]--array (row) pointer form
(4) Char **p--the form of a pointer pointer
Although these forms can represent two-dimensional arrays, they are not equivalent, and the transformation of two-dimensional arrays as parameters has a principle to follow. is to make the length of the array rows still recognizable in the child function.
(1) Char a[m][n]--void func (char (*p) [n]); It can also be written as void Func (char p[][n]) (the compiler automatically translates char p[][n] to char (*P) [n]), so this time sizeof (p) =4;sizeof (*P) is not 4 ha ...
(2) Char *a[n]--void func (char *p[]); it can also be written as void func (char **p), when sizeof (p) =4,sizeof (*p) = 4;
(3) char (*a) [n]--void func (char (*p) [n]); At this time sizeof (p) =4,sizeof (*p) =n;
(4) Char **a--void func (char **p);
In fact, 2 is a one-dimensional array of cases, 3 is a one-dimensional array pointer, 4 is a two-level pointer delivery.
The above * and [] interchangeable, written p[] situation can be changed to *p,*p can be changed to p[],
When you can write as p[], writing to any number of cases in [] does not affect the program. The compiler converts this situation to a *p case.
The general rule is that when you pass the array name in, you must allow the computer to recognize the length of the trip (the array is two-dimensional). The three-dimensional situation is similar, find the law, all cases can be solved.
Note: All the cases listed above are tested and passed under vc6.0.
Article Source: Fei Nuo network (www.firnow.com): http://dev.firnow.com/course/3_program/c++/cppjs/2007925/73641.html