(int) + 4*5;
Why is this (adding a type with a value) possible? (tried with g++ and gcc.)
I know that it doesn't make sense (and has no effect), but I want to know why this is possible.
The + here is unary + operator, not the binary addition operator. There's no addition happening here.
Also, the syntax (int) is used for typecasting.
You can re-read that statement as
(int) (+ 4) * 5;
which is parsed as
((int) (+ 4)) * (5);
which says,
+ operator on the integer constant value 4.int5This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.
In your case, the unary + and the cast to int - both are redundant.
This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.