Bo Sun <b0*****@cs.tamu.edu> wrote in message news:<Pi******************************@unix.cs.tam u.edu>...
suppose I have the following expression (all variables are of integer
type)
result = (first = 2, second = first + 1, third = second + 1);
what is the value of result?
1) result is 4. because the expressions are evaluated from left to right;
2) result is unpredictable. Because the comma operator returns the value
of he last expression. for the presivous expressions, there is no
guarantee of theorder of evaluation. Therefore, we could evaluate in the
following order:
One thing to keep in mind is the difference between the comma operator and
the commas used to seperate function arguments.
The comma operator guarantees the order of evaluation (left or right).
But the commas that separate the function arguments have no such guarantee.
So, in your example, after your statement, first will equal 2, second will
equal three, and both third and result will equal 4.
But if you change that around to this:
void some_func(int, int, int);
some_func(first = 2, second = first + 1, third = second + 1);
In this case, the value of the second and third arguments to some_func() and
the values of second and third after the call to some_func() have no guaranteed
value.
samuel