Operator <=> in Ruby

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What is the Ruby <=> (spaceship) operator?

I saw a code and an operator I'm unfamiliar with

 @array << {:suffix=> substring, :index => i}
 @array.sort! { |x,y| x[:suffix] <=> y[:suffix]}

I can't do google on it. What does <=> do?

[symbolhound.com](http://symbolhound.com/?q=ruby+%3C%3D%3E) is your friend — mu is too short, Nov 18 '12 at 18:39

score 5 · Answer 1 · answered Nov 18 '12 at 17:08

This is the spaceship operator, it was borrowed from Perl. It is commonly used for sorting, because it returns -1 if left operand is less than right operand, 1 if right operand is greater than the left and returns 0 otherwise.

1 <=> 2 # => -1
2 <=> 1 # => 1
1 <=> 1 # => 0

score 4 · Accepted Answer · answered Nov 18 '12 at 17:08

4

It does comparison defined for the particular class. If it is the case that ... < ... is true, it returns -1, if ... == ... is true, then 0, and if ... > ... is true, then 1.

answered Nov 18 '12 at 17:08

sawa

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There's a link in my answer :) – Sergio Tulentsev Nov 18 '12 at 17:31

score 1 · Answer 3 · answered Nov 18 '12 at 17:25

It's called the spaceship operator.

For the core numeric and string classes, it's a comparison operator that returns -1, 0, or 1.

In theory, a class can define any operator to do anything it wants, but this will be the method that is used when sorting. It may make sense to define <=> for an arbitrary application class if that class will ever need to be ordered.

Operator <=> in Ruby

3 Answers3