What does the % symbol mean in Ruby?

Question

What does the % symbol mean in Ruby? For example, I use the following code:

puts "Roosters #{100 - 25 * 3 % 4}"

And get the following output:

Where the deuce did the 97 come from? I've looked up what the modulo operator is and still have no idea what it does in this simple mathematics example.

http://stackoverflow.com/questions/2664301/how-does-modulus-divison-work — bruchowski, Oct 11 '14 at 05:27
[Fixnum#%](http://www.ruby-doc.org/core-2.1.1/Fixnum.html#method-i-25) is just another garden-variety method. — Cary Swoveland, Oct 11 '14 at 06:42

score 2 · Accepted Answer · answered Oct 11 '14 at 05:28

2

Modulo operator.

It does division and returns the remainder. So, in your case, 75 / 4 is 18 with a remainder of 3.

25 * 3 = 75

75 % 4 = 3 (the remainder)

100 - 3 = 97

answered Oct 11 '14 at 05:28

brian

2,745
2
17
33

codenheim · Answer 2 · 2014-10-11T05:38:30.907

modulo - divide with remainder

divide, and take the remainder from the integer division.

10 / 3 = 3 (with remainder 1 that we discard with integer division)
10 % 3 = 1 (the part we normally discard is the part we are interested in with mod)

It is also used to create cycles. If we had a sequence of 1 to N, we could mod it by M and produce a cycle. Assume M = 3 again

for n in 0..10
   m = n % 3
   puts "#{n} mod 3 = #{m}"
end

0 mod 3 = 0
1 mod 3 = 1
2 mod 3 = 2
3 mod 3 = 0
4 mod 3 = 1
5 mod 3 = 2
6 mod 3 = 0
7 mod 3 = 1
8 mod 3 = 2
9 mod 3 = 0
10 mod 3 = 1

What does the % symbol mean in Ruby?

2 Answers2