Passing Arrays to Function in C

Question

include  lt iostream gt  using namespace std   void printarray  int arg    int length        for  int n   0  n  lt  length  n              cout  lt  lt  arg n   lt  lt               cout  lt  lt    n            int main           int firstarray      5  10  15        int secondarray      2  4  6  8  10        printarray firstarray  3        printarray secondarray  5         return 0      This code works  but I want to understand how is the array being passed   When a call is made to the printarray function from the main function  the name of the array is being passed  The name of the array refers to the address of the first element of the array  How does this equate to int arg

User · Answer

firstarray and secondarray are converted to a pointer to int  when passed to printarray     printarray int arg         is equivalent to printarray int  arg        However  this is not specific to C    C has the same rules for passing array names to a function

User · Answer

The simple answer is that arrays are ALWAYS passed by reference and the int arg   simply lets the compiler know to expect an array

User · Answer

The syntaxes  int     and  int X     Where X is a compile-time positive integer   are exactly the same as  int    when in a function parameter list  I left out the optional names    Additionally  an array name decays to a pointer to the first element when passed to a function  and not passed by reference  so both int firstarray 3  and int secondarray 5  decay to int s   It also happens that both an array dereference and a pointer dereference with subscript syntax  subscript syntax is x y   yield an lvalue to the same element when you use the same index   These three rules combine to make the code legal and work how you expect  it just passes pointers to the function  along with the length of the arrays which you cannot know after the arrays decay to pointers

User · Answer

The question has already been answered  but I thought I d add an answer with more precise terminology and references to the C   standard   Two things are going on here  array parameters being adjusted to pointer parameters  and array arguments being converted to pointer arguments  These are two quite different mechanisms  the first is an adjustment to the actual type of the parameter  whereas the other is a standard conversion which introduces a temporary pointer to the first element   Adjustments to your function declaration   dcl fct 5      After determining the type of each parameter  any parameter of type    array of T          is adjusted to be    pointer to T       So int arg   is adjusted to be int  arg   Conversion of your function argument   conv array 1     An lvalue or rvalue of type    array of N T    or    array of unknown bound of T    can be converted to a prvalue of type    pointer to T     The temporary materialization conversion is applied  The result is a pointer to the first element of the array    So in printarray firstarray  3    the lvalue firstarray of type  array of 3 int  is converted to a prvalue  temporary  of type  pointer to int   pointing to the first element

User · Answer

I just wanna add this  when you access the position of the array like  arg n   is the same as     arg   n   than means an offset of n starting from de arg address   so arg 0  will be  arg

[c++] Passing Arrays to Function in C++

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