How to extract the sign of an integer in Ruby?

问题:

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 

Is there a built-in Ruby method which does that?

回答1:

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] # => "+" 

回答2:

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. 

回答3:

You could use Kernel#sprintf to format numbers:

def sign(i)   sprintf("%+d", i)[0] end  sign(100)  #=> "+" sign(-100) #=> "-" 

回答4:

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

回答5:

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.

回答6:

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 

文章来源: How to extract the sign of an integer in Ruby?