Question

How can I structure some C code so that I don’t have to laboriously go back and
redefine (i.e., #define) things when I need to add a new item in the middle.
Here is a code sample (in the real code, there are about 200 different
defines):

 #define CREAM   1
 #define SALT    2
 #define BUTTER  3
 #define SUGAR   4
 #define FAT     5

void healthyDiet()
{
    int length = 10;
    int menu[500];
    void consume(int, int);

    //   ******  these must be called in the following order only  
    consume( menu[ CREAM ],  length);
    consume( menu[ SALT ],   length);
    consume( menu[ BUTTER ], length);
    consume( menu[ SUGAR ],  length);
    consume( menu[ FAT ],    length);
}

But now I need to #define and add LARD, which would be straightforward if the sequence
here were not important. But LARD must come before SUGAR and after BUTTER. So
I now need to edit the defines:

#define CREAM    1
#define SALT     2
#define BUTTER  3
#define LARD    4
#define SUGAR   5   // changed from 4
#define FAT     6   // changed from 5

So how
can I structure things so that each time I want to add something in the middle, I
don’t have to go back and manually change the define value for each item?

Answer 1

You’re looking for enum

enum {CREAM, SALT, BUTTER, LARD, SUGAR};

To add anoter element, just add it:

enum {CREAM, SALT, BUTTER, LARD, BACON, SUGAR};

You can even use this like a psudeo-iterator:

enum {FIRST_ONE, CREAM=0, SALT, BUTTER, LARD, BACON, SUGAR, LAST_ONE};

void healthyDiet()
{
    int length = 10;
    int menu[500];
    void consume(int, int);

    int x;
    for(x=FIRST_ONE; x<LAST_ONE; x++)
        consume( menu[ x ],  length);
}