Why does -~x equal x+1?

Question

there is a statement "-~i == i+1 because of twos-complement".

Can someone explain why this is the case?

Did you read e.g. [the Wikipedia article on two's-complement](http://en.wikipedia.org/wiki/2%27s_complement)? — Oliver Charlesworth, Mar 19 '13 at 23:51
Sorry, i was trying to answer the question. I tried to add an answer to the other question but they said it was not an answer. — Thomas Song, Mar 19 '13 at 23:56

score 4 · Answer 1 · answered Mar 19 '13 at 23:54

4

-~x is equal to x+1 because ~x is equivalent to (0xffffffff-x). This is equal to (-1-x) in 2s complement, so -~x is -(-1-x) = x+1.

answered Mar 19 '13 at 23:54

Thomas Song

1 Answers1