As DK. points out, you don’t want wrapping semantics at the integer level: fn main() { let idx: usize = 0; let len = 10; let next_idx = idx.wrapping_sub(1) % len; println!(“{}”, next_idx) // Prints 5!!! } Instead, you want to use modulo logic to wrap around: let next_idx = (idx + len – 1) … Read more
The simple and correct answer is “because the C# Language Specification says so”. Clearly you are not happy with that answer and want to know “why does it say so”. You are looking for “credible and/or official sources”, that’s going to be a bit difficult. These design decisions were made a long time ago, 13 … Read more
First of all, note that we don’t see the same thing in Python 2.x: >>> timeit(“for i in range(1000): 2*i*i”) 51.00784397125244 >>> timeit(“for i in range(1000): 2*(i*i)”) 50.48330092430115 So this leads us to believe that this is due to how integers changed in Python 3: specifically, Python 3 uses long (arbitrarily large integers) everywhere. For … Read more
Math.addExact throws exception on overflow Since Java 8 there is a set of methods in the Math class: toIntExact(long) addExact(int,int) subtractExact(int,int) multiplyExact(int,int) …and versions for long as well. Each of these methods throws ArithmeticException if overflow happens. Otherwise they return the proper result if it fits within the range. Example of addition: int x = … Read more
The compiler will, in this case, evaluate the calculation (because it contains only constants) and try to assign the result to the variable. This calculation is done with type int and only converted to short on assignment, if at all possible. In your case, the first calculation is too large to fit into a short … Read more
As Miles hinted: The C++ code text is bound by the rules of the C++ language (integer overflow = bad), but the compiler is only bound by the rules of the cpu (overflow=ok). It is allowed to make optimizations that the code isn’t allowed to. But don’t take this as an excuse to get lazy. … Read more
Speaking to the C side of the problem, Is my reasoning correct, and is this a legitimate problem in theory? It is a problem that I had not considered before, but I agree with your analysis. C defines the behavior of the << operator in terms of the type of the promoted left operand, and … Read more
I liked this question so much I made it the subject of my blog on June 4th, 2013. Thanks for the great question! Large cases are easy to come by. For example: a = 1073741823; b = 134217727; c = 134217727; because b * c overflows to a negative number. I would add to that … Read more
For the first one, to check if a number is a multiple of use: if (num % 10 == 0) // It’s divisible by 10 For the second one: if(((num – 1) / 10) % 2 == 1 && num <= 100) But that’s rather dense, and you might be better off just listing the … Read more
When you work with unsigned types, modular arithmetic (also known as “wrap around” behavior) is taking place. To understand this modular arithmetic, just have a look at these clocks: 9 + 4 = 1 (13 mod 12), so to the other direction it is: 1 – 4 = 9 (-3 mod 12). The same principle … Read more