conditional operator in c

[arch07]

if anyone knows plz explain this conditional operator
timeout ? : MAX SCHEDULE_TIMEOUT

[GNU-Fan]

This operator (?) is somewhat special, because it is "ternary". Most operators are unary or binary.
Unary means the operator works on one argument. Like a++ increments a, and only a, by one.
Binary operators do work with two arguments. Like (+) in 4+3. This would give you a 7 as "result".

This operator has three arguments. Let's call them #1, #2, #3. What the ? does is:
The result of (#1 ? #2 #3) is: #2 if #1 is "true", #3 if #1 is "false".

You will understand it better if you assign the value to some variable.
result = timeout ? : MAX SCHEDULE_TIMEOUT;
This is a short form of

if (timeout) 
  result = MAX;
else
  result = SCHEDULE_TIMEOUT;

[Cabhan]

I don't know if it's intentional or not, but the syntax that you're using is slightly wrong.

In the following code:

result = (timeout != 0) ? timeout : MAX_SCHEDULE_TIMEOUT

Note that the true result needs to be between the ? and the :, and the false result needs to be after the :.

[KPolulak]

I struggled with the ternary operator too when I was first learning C/C++.

The way I remember it is by thinking:

IF ? THEN : ELSE

Also, if you have trouble remembering which symbol comes first, the ? or the :, then think of the statement as a question. "What if?" You'll remember that it's ? then :.