proc.c: Implement Method#* for Method composition

* proc.c (rb_method_compose): Implement Method#* for Method composition,
  which delegates to Proc#*.

* test/ruby/test_method.rb: Add test cases for Method composition.

From: Paul Mucur <mudge@mudge.name>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65912 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

proc.c

@@ -3099,6 +3099,30 @@ proc_compose(VALUE self, VALUE g)
     return proc;
 }
 
+/*
+ *  call-seq:
+ *     meth * g -> a_proc
+ *
+ *  Returns a proc that is the composition of this method and the given proc <i>g</i>.
+ *  The returned proc takes a variable number of arguments, calls <i>g</i> with them
+ *  then calls this method with the result.
+ *
+ *     def f(x)
+ *       x * 2
+ *     end
+ *
+ *     f = self.method(:f)
+ *     g = proc {|x, y| x + y }
+ *     h = f * g
+ *     p h.call(1, 2) #=> 6
+ */
+static VALUE
+rb_method_compose(VALUE self, VALUE g)
+{
+    VALUE proc = method_to_proc(self);
+    return proc_compose(proc, g);
+}
+
 /*
  *  Document-class: LocalJumpError
  *
@@ -3222,6 +3246,7 @@ Init_Proc(void)
     rb_define_method(rb_cMethod, "call", rb_method_call, -1);
     rb_define_method(rb_cMethod, "===", rb_method_call, -1);
     rb_define_method(rb_cMethod, "curry", rb_method_curry, -1);
+    rb_define_method(rb_cMethod, "*", rb_method_compose, 1);
     rb_define_method(rb_cMethod, "[]", rb_method_call, -1);
     rb_define_method(rb_cMethod, "arity", method_arity_m, 0);
     rb_define_method(rb_cMethod, "inspect", method_inspect, 0);

test/ruby/test_method.rb

@@ -1040,4 +1040,38 @@ class TestMethod < Test::Unit::TestCase
     assert_operator(0.method(:<), :===, 5)
     assert_not_operator(0.method(:<), :===, -5)
   end
+
+  def test_compose_with_method
+    c = Class.new {
+      def f(x) x * 2 end
+      def g(x) x + 1 end
+    }
+    f = c.new.method(:f)
+    g = c.new.method(:g)
+    h = f * g
+
+    assert_equal(6, h.call(2))
+  end
+
+  def test_compose_with_proc
+    c = Class.new {
+      def f(x) x * 2 end
+    }
+    f = c.new.method(:f)
+    g = proc {|x| x + 1}
+    h = f * g
+
+    assert_equal(6, h.call(2))
+  end
+
+  def test_compose_with_nonproc_or_method
+    c = Class.new {
+      def f(x) x * 2 end
+    }
+    f = c.new.method(:f)
+
+    assert_raise(TypeError) {
+      f * 5
+    }
+  end
 end