Unexpected result from math expression

Question

i am using ruby irb

   -1/4
=> -1
   0-1
=> -1
   0-1/4
=> 0

How come it'll be zero for 0-1/4 ?

My calculation is as shown in below pic

Answer 1

1/4 is zero - since both operands are integers, the result is floored to an integer as well. This is the same behavior you're observing earlier with -1/4.

If you want a non-integer result, one or both of the operands have to be floats. For example:

0 - 1 / 4.to_f

to_f makes the interpreter interpret the number as a float.

edit: Your calculation is wrong, by the way. 0 - 1/4 is NOT the same as (0-1) / 4. Always do your operations in the correct order!

Answer 2

Because 1 / 4 is 0. And 0 - 0 is 0.

0 - (1 / 4)

You want this:

(0 - 1) / 4

This way you make sure that subtraction happens first. Read up on operator precedence.