subtraction

问题 Suppose that A and B are signed positive integers, then for A-B , it's calculated using A+2 's complement of B . For example, in a 4-bit binary system, for signed integers, we have 7-3=0111-0011=0111+1101=(1)0100 , the 1 in the bracket is the carry bit. According to the overflow rule for signed integer, we know there is no overflow and the result is therefore correct. However, for unsigned integers, what will happen if we calculate 7-3 ? If we use the same way we mentioned above: 7-3=0111

问题 Why is q == 0 in the following script? <script> var start = 1234567890123456789; var end = 1234567890123456799; var q = end - start; alert(q); </script> I would think the result should be 10. What is the correct way to subtract these two numbers? 回答1: Because numbers in JavaScript are floating-point. They have limited precision. When JavaScript sees a very long number, it rounds it to the nearest number it can represent as a 64-bit float. In your script, start and end get rounded to the same

问题 I'm trying to write a Date class in an attempt to learn C++. I'm trying to find an algorithm to add or subtract days to a date, where Day starts from 1 and Month starts from 1. It's proving to be very complex, and google doesn't turn up much, Does anyone know of an algorithm which does this? 回答1: The easiest way is to actually write two functions, one which converts the day to a number of days from a given start date, then another which converts back to a date. Once the date is expressed as a

问题 Possible Duplicate: How can I divide each row of a matrix by a fixed row? I\'m looking for an elegant way to subtract the same vector from each row of a matrix. Here is a non elegant way of doing it. a = [1 2 3]; b = rand(7,3); c(:,1) = b(:,1) - a(1); c(:,2) = b(:,2) - a(2); c(:,3) = b(:,3) - a(3); Also, the elegant way can\'t be slower than this method. I\'ve tried c = b-repmat(a,size(b,1),1); and it seems slower. EDIT: The winner is this method. c(:,1) = b(:,1) - a(1); c(:,2) = b(:,2) - a(2

问题 Anyone know a simple way using Java calendar to subtract X days from a date? I have not been able to find any function which allows me to directly subtract X days from a date in Java. Can someone point me to the right direction? 回答1: Taken from the docs here: Adds or subtracts the specified amount of time to the given calendar field, based on the calendar's rules. For example, to subtract 5 days from the current time of the calendar, you can achieve it by calling: Calendar calendar = Calendar