Thread: passing arrays into functions by reference

for some reason, i can't figure out how to pass an array into a function properly.

here's the code where i'm encountering the error:

function declaration:

Code:

void initMapBuffer(map map1, CHAR_INFO &mapBuffer[]);

function body:

Code:

void initMapBuffer(map map1, CHAR_INFO &mapBuffer[])
{
 for (int y = 0; y < map1.max.Y; y++)
 {
  for (int x = 0; x < map1.max.X; x++)
  {
   mapBuffer[x + y * MAP_BUFFER_W].Char.AsciiChar = map1.tiles[x][y].symbol;
  }
 }
}

the map struct:

Code:

struct map
{
 tile tiles[MAP_MAX_X][MAP_MAX_Y];
 COORD max;
};

the tile struct

Code:

struct tile
{
 char symbol;
 char foreground, background;
};

please answer this question. I usually can figure these things out myself, but i'm stumped on this one. This piece of code is the cornerstone for my RPG, without it, i can't load maps and display them to the screen.

CHAR_INFO &mapBuffer[]

is an array of references, which isn't legal C++. You could try something like

CHAR_INFO (&mapBuffer)[SIZE]

if you're willing to commit a size to the arrays that'll be passed into the function, but as arrays are really passed by address they're passed by reference anyway so I see no reason not to just do

CHAR_INFO mapBuffer[]

oh.. i thought that you passed arrays by value if you didn't use the address of (&) operator. Alright, i'll try it out.

alright, now i'm getting an illegal operation when i execute it.

By default array's are passed by reference. All an array is, is a pointer to the first element in a series.

i'm using buffers to display the map for my roguelike to the screen, an array of CHAR_INFO stores what charactars and their attributes will go into each character slot in the buffer.

Originally posted by Aran Elus
oh.. i thought that you passed arrays by value if you didn't use the address of (&) operator. Alright, i'll try it out.

When you pass array's to a function, all you are really passing is the address of the first element. The compiler lets you use array notation ( arrayname[int] ) to make coding easier, If you change a value in the array in the function, the array from the calling function will be modifed as well.
So try this

void functionName( type * arrayname)

This will be ok if you know how big the array is going to be, or you could pass a size paramater along with the array name

void functionName( type * arrayname, int size)