Add initial value for product and sum on L

Author: radekosmulski

fastcore/foundation.py

@@ -186,8 +186,8 @@ def shuffle(self):
 
     def concat(self): return self._new(itertools.chain.from_iterable(self.map(L)))
     def reduce(self, f, initial=None): return reduce(f, self) if initial is None else reduce(f, self, initial)
-    def sum(self): return self.reduce(operator.add)
-    def product(self): return self.reduce(operator.mul)
+    def sum(self): return self.reduce(operator.add, 0)
+    def product(self): return self.reduce(operator.mul, 1)
     def setattrs(self, attr, val): [setattr(o,attr,val) for o in self]
 
 # Cell

nbs/02_foundation.ipynb

@@ -634,8 +634,8 @@
     "\n",
     "    def concat(self): return self._new(itertools.chain.from_iterable(self.map(L)))\n",
     "    def reduce(self, f, initial=None): return reduce(f, self) if initial is None else reduce(f, self, initial)\n",
-    "    def sum(self): return self.reduce(operator.add)\n",
-    "    def product(self): return self.reduce(operator.mul)\n",
+    "    def sum(self): return self.reduce(operator.add, 0)\n",
+    "    def product(self): return self.reduce(operator.mul, 1)\n",
     "    def setattrs(self, attr, val): [setattr(o,attr,val) for o in self]"
    ]
   },
@@ -883,6 +883,16 @@
     "test_shuffled(t,t.shuffle())"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "test_eq(L([]).sum(), 0)\n",
+    "test_eq(L([]).product(), 1)"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,