How to extract the sign of an integer in Ruby?

Question

I need a function which returns/prints the sign on an integer. So far I came up with this:

def extract_sign(integer)
  integer >= 0 ? \'+\' : \'-\'
end


        

Answer 1

I think that it's nonsense not to have a method that just gives -1 or +1. Even BASIC has such a function SGN(n). Why should we have to deal with Strings when it's numbers we want to work with. But's that's just MHO.

def sgn(n)
  n <=> 0
end.

Answer 2

Ruby doesn't have a built in sign function like Javascript. Here's a thread that explains more http://www.ruby-forum.com/topic/141216

Your approach looks correct.

Answer 3

Here is a simple way to do it:

x = -3
"++-"[x <=> 0] # => "-"

x = 0
"++-"[x <=> 0] # => "+"

x = 3
"++-"[x <=> 0] # => "+"

or

x = -3
"±+-"[x <=> 0] # => "-"

x = 0
"±+-"[x <=> 0] # => "±"

x = 3
"±+-"[x <=> 0] # => "+"

Answer 4

I use n == 0 ? 1 : n.abs / n, e.g.:

def sign(n)
  n == 0 ? 1 : n.abs / n
end

sign(10) # 1
sign(0) # 1
sign(-5) # -1

Answer 5

You could use Kernel#sprintf to format numbers:

def sign(i)
  sprintf("%+d", i)[0]
end

sign(100)  #=> "+"
sign(-100) #=> "-"

Answer 6

class Numeric
  def sign
    if self > 0
      '+'
    elsif zero?
      nil
    else
      '-'
    end
  end
end