小编ZYK*_*YKY的帖子

我有一个几乎全新的django安装,当我尝试python manage.py runserver.It是给我这个错误:

配置不正确:无法加载WSGI应用程序'myproject.wsgi.application'; 导入模块时出错.

settings.py

WSGI_APPLICATION = 'myproject.wsgi.application'

wsgi.py

import os
from django.core.wsgi import get_wsgi_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "myproject.settings")
application = get_wsgi_application()

我有以下二叉树的定义和一个获取最左边元素的函数，或者如果树是空树则返回 Nothing，但是它说x(with type a) 是无限类型，因为它返回Maybe a?

谢谢任何帮助，将不胜感激:)

data Tree a = EmptyTree | Node a (Tree a) (Tree a) deriving (Show, Eq)\n\nleftistElement :: (Ord a) => Tree a -> Maybe a\nleftistElement EmptyTree = Nothing\nleftistElement (Node x left _) =\n  if left == EmptyTree\n    then x\n    else leftistElement left\n

types.hs:55:10: error:\n    \xe2\x80\xa2 Occurs check: cannot construct the infinite type: a ~ Maybe a\n    \xe2\x80\xa2 In the expression: x\n      In the expression:\n        if left …