Just to give you a “real-world” example, consider this program: int main() { int i = 0; i += 1; i++; i = i + 1; return 0; } Compiling it with GCC, in Darwin 11 with the following flags: -S stop in assembler -m32 to 32-bit platform, just to simplify things a bit Will … Read more
i += 4; means i = i + 4; // increase i by 4. While i =+ 4; is equivalent to i = +4; // assign 4 to i. the unary plus is effectively no-op. (See http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.15.3 for what a unary + does.)
Two inc instructions on the same register (or more generally speaking two read-modify-write instructions) do always have a dependency chain of at least two cycles. This is assuming a one clock latency for a inc, which is the case since the 486. That means if the surrounding instructions can’t be interleaved with the two inc … Read more
The write is atomic but an increment also requires a read. So the question is: Are you sure the read is safe, in other words, are you sure another thread doing the increment will not end up with the same value to be incremented? I have doubts. The 100% correct way of doing this would … Read more
The typical answer to this question, unfortunately posted here already, is that one does the increment “before” remaining operations and the other does the increment “after” remaining operations. Though that intuitively gets the idea across, that statement is on the face of it completely wrong. The sequence of events in time is extremely well-defined in … Read more
It is more idiomatic to call the prefix increment of the object itself in the postfix increment: X operator++(int) { X copy(*this); ++*this; // call the prefix increment return copy; } The logic of incrementing an X object is thus solely contained inside the prefix version.
You’re looking for variable indirection, i.e. the ability to refer to a variable indirectly, by a name stored in another variable or returned from an expression. Note, however, that there are usually superior alternatives, such as using arrays or hashtables as multi-value containers – see this answer for an example. If you do need to … Read more
Any sane or insane compiler will produce identical machine code for both.
You should append all the values to a list, that allows you to easily iterate through the values later as well as not littering your namespace with useless variables and magic.
The behavior is well defined in C# and the evaluation order is: Left side i is evaluated to the variable i Right side is evaluated to 0, and i is incremented (now i==1) The assignment is executed, it sets i to 0. (now i==0) The end result is i==0. In general you first create an … Read more