Make generator protocol interface and adjust generator.go to use it

Author: ncw

py/generator.go

@@ -76,7 +76,7 @@ func (it *Generator) M__next__() Object {
 // without yielding another value. When send() is called to start the
 // generator, it must be called with None as the argument, because
 // there is no yield expression that could receive the value.
-func (it *Generator) Send(value Object) {
+func (it *Generator) Send(value Object) Object {
 	panic("generator send not implemented")
 }
 
@@ -88,7 +88,7 @@ func (it *Generator) Send(value Object) {
 // StopIteration exception is raised. If the generator function does
 // not catch the passed-in exception, or raises a different exception,
 // then that exception propagates to the caller.
-func (it *Generator) Throw(args Tuple, kwargs StringDict) {
+func (it *Generator) Throw(args Tuple, kwargs StringDict) Object {
 	panic("generator throw not implemented")
 }
 
@@ -102,9 +102,9 @@ func (it *Generator) Throw(args Tuple, kwargs StringDict) {
 // generator raises any other exception, it is propagated to the
 // caller. close() does nothing if the generator has already exited
 // due to an exception or normal exit.
-func (it *Generator) Close() {
+func (it *Generator) Close() Object {
 	panic("generator close not implemented")
 }
 
 // Check interface is satisfied
-var _ I_iterator = (*Generator)(nil)
+var _ I_generator = (*Generator)(nil)

py/internal.go

@@ -247,3 +247,15 @@ func Next(self Object) Object {
 	// FIXME should be TypeError
 	panic(fmt.Sprintf("TypeError: '%s' object is not iterable", self.Type().Name))
 }
+
+// Call send for the python object
+func Send(self, value Object) Object {
+	if I, ok := self.(I_send); ok {
+		return I.Send(value)
+	} else if res, ok := TypeCall1(self, "send", value); ok {
+		return res
+	}
+
+	// FIXME should be TypeError
+	panic(fmt.Sprintf("TypeError: '%s' object doesn't have send method", self.Type().Name))
+}

py/py.go

@@ -560,6 +560,25 @@ type I_iterator interface {
 	I__next__
 }
 
+// Generator interfaces
+type I_send interface {
+	Send(value Object) Object
+}
+type I_throw interface {
+	Throw(args Tuple, kwargs StringDict) Object
+}
+type I_close interface {
+	Close() Object
+}
+
+// Interface all generators must satisfy
+type I_generator interface {
+	I_iterator
+	I_send
+	I_throw
+	I_close
+}
+
 // Called (if present) by the reversed() built-in to implement reverse
 // iteration. It should return a new iterator object that iterates
 // over all the objects in the container in reverse order.