Implement Complex#<=>

Implement Complex#<=> so that it is usable as an argument when
calling <=> on objects of other classes (since #coerce will coerce
such numbers to Complex).  If the complex number has a zero imaginary
part, and the other argument is a real number (or complex number with
zero imaginary part), return -1, 0, or 1.  Otherwise, return nil,
indicating the objects are not comparable.

Fixes [Bug #15857]

1 files changed, 27 insertions, 0 deletions

diff --git a/spec/ruby/core/complex/spaceship_spec.rb b/spec/ruby/core/complex/spaceship_spec.rb
new file mode 100644
index 0000000000..7b2849a86a
--- /dev/null
+++ b/spec/ruby/core/complex/spaceship_spec.rb
@@ -0,0 +1,27 @@
+require_relative '../../spec_helper'
+
+describe "Complex#<=>" do
+  ruby_version_is '2.7' do
+    it "returns nil if either self or argument has imaginary part" do
+      (Complex(5, 1) <=> Complex(2)).should be_nil
+      (Complex(1) <=> Complex(2, 1)).should be_nil
+      (5 <=> Complex(2, 1)).should be_nil
+    end
+
+    it "returns nil if argument is not numeric" do
+      (Complex(5, 1) <=> "cmp").should be_nil
+      (Complex(1) <=> "cmp").should be_nil
+      (Complex(1) <=> Object.new).should be_nil
+    end
+
+    it "returns 0, 1, or -1 if self and argument do not have imaginary part" do
+      (Complex(5) <=> Complex(2)).should == 1
+      (Complex(2) <=> Complex(3)).should == -1
+      (Complex(2) <=> Complex(2)).should == 0
+
+      (Complex(5) <=> 2).should == 1
+      (Complex(2) <=> 3).should == -1
+      (Complex(2) <=> 2).should == 0
+    end
+  end
+end