fix bug in variable addressing if they weren't immediately written to

builtins.go

@@ -679,7 +679,7 @@ func (b *Builtins) Variable(c *Context) func(string) error {
 				c.Dictionary.AddWord(string(w), Word{Name: string(w), Variable: next})
 				j, _ := c.RStack.Pop()
 				c.RStack.Push(j + i - 1) // push the end-point onto the stack
-				return nil
+				return c.Memory.Write(next, []int{0})
 			default:
 				w = append(w, next[i])
 				continue

mem.go

@@ -28,7 +28,7 @@ func (m *Memory) Write(addr int, values []int) error {
 		m.intern[addr+i] = values[i]
 	}
 	// we've written past our marker, note that
-	if m.nextFree < addr+len(values) {
+	if m.nextFree <= addr+len(values) {
 		m.nextFree = addr + len(values)
 	}
 	return nil