Merge pull request #4211 from dearblue/proc-composition

Add proc composition feature (CRuby-2.6 compatible)

mrbgems/mruby-method/mrblib/method.rb

@@ -17,4 +17,12 @@ class Method
   def name
     @name
   end
+
+  def <<(other)
+    ->(*args, &block) { call(other.call(*args, &block)) }
+  end
+
+  def >>(other)
+    ->(*args, &block) { other.call(call(*args, &block)) }
+  end
 end

mrbgems/mruby-method/test/method.rb

@@ -371,6 +371,25 @@ assert "Method#initialize_copy" do
   assert_equal(m1, m2)
 end
 
+assert "Method#<< and Method#>>" do
+  obj = Object.new
+  class << obj
+    def mul2(n); n * 2; end
+    def add3(n); n + 3; end
+  end
+
+  f = obj.method(:mul2)
+  g = obj.method(:add3)
+
+  m1 = f << g
+  assert_kind_of Proc, m1
+  assert_equal 16, m1.call(5)
+
+  m2 = f >> g
+  assert_kind_of Proc, m2
+  assert_equal 13, m2.call(5)
+end
+
 assert 'UnboundMethod#arity' do
   c = Class.new {
     def foo(a, b)

mrbgems/mruby-proc-ext/mrblib/proc.rb

@@ -39,4 +39,12 @@ class Proc
     make_curry.call
   end
 
+  def <<(other)
+    ->(*args, &block) { call(other.call(*args, &block)) }
+  end
+
+  def >>(other)
+    ->(*args, &block) { other.call(call(*args, &block)) }
+  end
+
 end

mrbgems/mruby-proc-ext/test/proc.rb

@@ -77,6 +77,19 @@ assert('Kernel#proc') do
   end
 end
 
+assert "Proc#<< and Proc#>>" do
+  add3 = ->(n) { n + 3 }
+  mul2 = ->(n) { n * 2 }
+
+  f1 = mul2 << add3
+  assert_kind_of Proc, f1
+  assert_equal 16, f1.call(5)
+
+  f2 = mul2 >> add3
+  assert_kind_of Proc, f2
+  assert_equal 13, f2.call(5)
+end
+
 assert('mrb_proc_new_cfunc_with_env') do
   ProcExtTest.mrb_proc_new_cfunc_with_env(:test)
   ProcExtTest.mrb_proc_new_cfunc_with_env(:mruby)