spaceship operatorとは 意味・読み方・使い方

The spaceship operator, written <=>, is a binary relational operator that originated in the Perl programming language. Other languages, such as Ruby and Groovy also support the spaceship operator. Unlike traditional equality operators, which will return 1 (true) or 0 (false) depending on whether the arguments are equal or unequal, the spaceship operator will return 1, 0, or −1 depending on the value of the left argument relative to the right argument. If the left argument is greater than the right argument, the operator returns 1. If the left argument is less than the right argument, the operator returns −1. If the two arguments are equal, the operator returns 0. If the two arguments cannot be compared (e.g. one of them is NaN), the operator returns undef.