Question

I’m looking at something like this:

#define foo(x)   \
    (((a > b) ?  \
      0 : 1),    \
     (c ? 2 : 3), \
     (d ? 4 : 5))

I’m not sure how to interpret this. Can someone help me out?

Answer 1

Essentially the \ ignores the newline as far as terminating the #define statement is concerned, so each time you write foo(var) in your code it will be replaced with

((((a > b) ?  
  0 : 1),    
 (c ? 2 : 3), 
 (d ? 4 : 5))

The comma operator doesn’t do a whole lot, except the final “returned” value of a statement consisting of statements separated by comma operators is the right most value.

All of that being explained, this isn’t really a terribly valid #define since you use a,b,c, and d in the #define and only reference x as a parameter