C pass an array by reference

Question

is this allowed to pass an array by reference     void foo double amp   bar     Seems that my compiler says no  Why  What is the proper way to pass an array by reference  Or a work around  I have an array argument that my method should modify and that I should retrieve afterwards  Alternatively  I could make this array a class member  which works fine  but it has many drawbacks for other part of my code  that I would like to avoid    Thanks and regards

User · Answer

Here  Erik explains every way pass an array by reference  https   stackoverflow com a 5724184 5090928   Similarly  you can create an array reference variable like so   int arr1      1  2  3  4  5   int  amp arr2  5    arr1

User · Answer

If you want to modify just the elements   void foo double  bar     is enough   If you want to modify the address to  e g   realloc   but it doesn t work for arrays   void foo double   amp bar     is the correct form

User · Answer

Yes  but when argument matching for a reference  the implicit array to pointer isn t automatic  so you need something like   void foo  double   amp array  42       or  void foo  double   amp array         Be aware  however  that when matching  double  42  and double    are distinct types   If you have an array of an unknown dimension  it will  match the second  but not the first  and if you have an array with 42 elements  it will match the first but not the second    The latter is  IMHO  very counter-intuitive    In the second case  you ll also have to pass the dimension  since there s no way to recover it once you re inside the function

User · Answer

As you are using C    the obligatory suggestion that s still missing here  is to use std  vector lt double gt    You can easily pass it by reference   void foo std  vector lt double gt  amp  bar       And if you have C  11 support  also have a look at std  array   For reference    http   de cppreference com w cpp container vector http   de cppreference com w cpp container array

User · Answer

Arrays can only be passed by reference  actually   void foo double   amp bar  10         This prevents you from doing things like   double arr 20   foo arr      won t compile   To be able to pass an arbitrary size array to foo  make it a template and capture the size of the array at compile time   template lt typename T  size t N gt  void foo T   amp bar  N            use N here     You should seriously consider using std  vector  or if you have a compiler that supports c  11  std  array

User · Answer

Like the other answer says  put the  amp  after the     This brings up an interesting point that can be confusing sometimes  types should be read from right to left  For example  this is  starting from the rightmost    a pointer to a constant pointer to an int   int   const  x    What you wrote would therefore be a pointer to a reference  which is not possible

User · Answer

8 3 5 8 If the type of a parameter includes a type of the form    pointer to array of unknown bound of T    or    reference to array of unknown bound of T     the program is ill-formed

[c++] C++ pass an array by reference

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