Why modulus operation work different in ruby than other languages?

问题

In Ruby, I get:

-5 % 3 # => 1

whereas other languages like PHP, Javascript, C++, and Java all produce the result -2. I don't understand this concept. I hope someone can explain this ruby's calculation method. It would be better if you could use an example of how it works.

回答1:

It's in the docs: https://ruby-doc.org/core-2.5.0/Numeric.html#method-i-divmod

If q, r = x.divmod(y), then

q = floor(x/y)
x = q*y + r

The quotient is rounded toward negative infinity

So q is -3 (-5 / 2 and round down, as per usual integer division rules). And r = x - q * y = -5 - -3 * 2 = 1

来源：https://stackoverflow.com/questions/53378554/why-modulus-operation-work-different-in-ruby-than-other-languages