Implement len() and py.Len

Author: ncw

builtin/builtin.go

@@ -42,7 +42,7 @@ func init() {
 		// py.NewMethod("isinstance", builtin_isinstance, 0, isinstance_doc),
 		// py.NewMethod("issubclass", builtin_issubclass, 0, issubclass_doc),
 		// py.NewMethod("iter", builtin_iter, 0, iter_doc),
-		// py.NewMethod("len", builtin_len, 0, len_doc),
+		py.NewMethod("len", builtin_len, 0, len_doc),
 		// py.NewMethod("locals", builtin_locals, py.METH_NOARGS, locals_doc),
 		// py.NewMethod("max", builtin_max, 0, max_doc),
 		// py.NewMethod("min", builtin_min, 0, min_doc),
@@ -549,3 +549,11 @@ func builtin_compile(self py.Object, args py.Tuple, kwargs py.StringDict) py.Obj
 
 	return result
 }
+
+const len_doc = `len(object) -> integer
+
+Return the number of items of a sequence or mapping.`
+
+func builtin_len(self, v py.Object) py.Object {
+	return py.Len(v)
+}

notes.txt

@@ -31,6 +31,19 @@ When converting C code, run it through astyle first as a first pass
 
 astyle --style=java --add-brackets < x.c > x.go
 
+Roadmap
+=======
+  * FIXME catching an exception is stopping the error return / traceback working
+  * FIXME (int("a", base=16): gives int() got multiple values for argument 'base'
+  * make pystone.py work
+  * make enough of internals work so can run python tests
+  * import python tests and write go test runner to run them
+  * make lots of them pass
+
+Missing parts
+=============
+  * repr/str
+  * subclassing built in types
 
 Polymorphism
 ============

py/internal.go

@@ -75,6 +75,16 @@ func IndexIntCheck(a Object, max int) int {
 	return i
 }
 
+// Returns the number of items of a sequence or mapping
+func Len(self Object) Object {
+	if I, ok := self.(I__len__); ok {
+		return I.M__len__()
+	} else if res, ok := TypeCall0(self, "__len__"); ok {
+		return res
+	}
+	panic(ExceptionNewf(TypeError, "object of type '%s' has no len()", self.Type().Name))
+}
+
 // Return the result of not a
 func Not(a Object) Object {
 	switch MakeBool(a) {