Merge pull request #109 from LLFourn/master

added example of type coercions for non builtin types

Author: LLFourn

lib/Language/functions.pod

@@ -558,8 +558,30 @@ C<Cool> is the type that the routine accepts as input.
 If the accepted input type is L<Any|/type/Any>, you can abbreviate C<Int(Any)>
 to C<Int()>.
 
-Coercion types are supposed to work wherever types work, but Rakudo currently
-(2015.02) only implements them for subroutine parameters.
+The coercion works simply by looking for a method with the same name
+as the target type. So you can define coercions for your own types like so:
+
+    class MyModule::Foo {
+       has $.msg = "I'm a foo!";
+
+       method MyModule::Bar {
+          ::('MyModule::Bar').new(:msg($.msg ~ ' But I am now Bar.'));
+       }
+    }
+
+    class MyModule::Bar {
+       has $.msg;
+    }
+
+    sub print-bar(MyModule::Bar() $bar) {
+       say $bar.WHAT; #MyModule::Bar
+       say $bar.msg;  #I'm a foo! But I am now Bar.
+    }
+
+    print-bar MyModule::Foo.new;
+
+Coercion types are supposed to work wherever types work, but Rakudo
+currently (2015.02) only implements them for subroutine parameters.
 
 =end pod