py: Fix __mul__ of list and tuple on negative case (#67)

Author: corona10

py/list.go

@@ -259,6 +259,9 @@ func (l *List) M__mul__(other Object) (Object, error){
 ifb, ok:=convertToInt(other); ok{
 m:=len(l.Items)
 n:=int(b) *m
+ifn<0{
+n=0
+ }
 newList:=NewListSized(n)
 fori:=0; i<n; i+=m{
 copy(newList.Items[i:i+m], l.Items)

py/tests/list.py

@@ -33,4 +33,10 @@
 assertrepr(a) =="['a', 'b', 'c', 'd', 'e', 'f']"
 assertRaises(TypeError, lambda: [].append())
 
+doc="mul"
+a= [1, 2, 3]
+asserta*2== [1, 2, 3, 1, 2, 3]
+asserta*0== []
+asserta*-1== []
+
 doc="finished"

py/tests/tuple.py

@@ -14,4 +14,10 @@
 assertrepr((1,(2,3),4)) =="(1, (2, 3), 4)"
 assertrepr(("1",(2.5,17,()))) =="('1', (2.5, 17, ()))"
 
+doc="mul"
+a= (1, 2, 3)
+asserta*2== (1, 2, 3, 1, 2, 3)
+asserta*0== ()
+asserta*-1== ()
+
 doc="finished"

py/tuple.go

@@ -113,6 +113,7 @@ func (a Tuple) M__add__(other Object) (Object, error){
 copy(newTuple[len(b):], b)
 returnnewTuple, nil
  }
+
 returnNotImplemented, nil
 }
 
@@ -131,6 +132,9 @@ func (l Tuple) M__mul__(other Object) (Object, error){
 ifb, ok:=convertToInt(other); ok{
 m:=len(l)
 n:=int(b) *m
+ifn<0{
+n=0
+ }
 newTuple:=make(Tuple, n)
 fori:=0; i<n; i+=m{
 copy(newTuple[i:i+m], l)