<=>

<=> is spaceship operator of Ruby. This is general purpose comparison operator. It compares two values and returns -1, 0, +1 depending on whether value1 is less then, equal or grater than value2.

value1 <=> value2 => -1 : if value1 < value2

   0 : if value1 = value2 

 +1 : if value1 > value2 

This operator is equivalent to ICompare.Compare( Object x, Object y) methods of .NET library.