This is allowed:
int a, b, c;
a = b = c = 16;
string s = null;
while ((s = "Hello") != null) ;
To my understanding, assignment s = ”Hello”; should only cause “Hello” to be assigned to s, but the operation shouldn’t return any value. If that was true, then ((s = "Hello") != null) would produce an error, since null would be compared to nothing.
What is the reasoning behind allowing assignment statements to return a value?
The fact that 'a++' or 'printf("foo")' may be useful either as a self-contained statement or as a part of a larger expression means that C has to allow for the possibility that expression results may or may not be used. Given that, there's a general notion that expressions which might usefully 'return' a value may as well do so. Assignment chaining can be slightly "interesting" in C, and even more interesting in C++, if all the variables in question do not have precisely the same type. Such usages are probably best avoided.