小编Jan*_*ane的帖子

我最近在查看模型摘要时遇到了这种情况。

[(None, 16)]我想知道和之间有什么区别(None, 16)？为什么输入层有这样的输入形状？

来源：model.summary() 在使用子类模型时无法打印输出形状

我试图创建自己的Writer类型,然后我也为它创建了一个实例.无论如何,我继续得到这个错误:

Illegal instance declaration for ‘Monad (Writer String)’
  (All instance types must be of the form (T a1 ... an)
   where a1 ... an are *distinct type variables*,
   and each type variable appears at most once in the instance head.
   Use FlexibleInstances if you want to disable this.)
In the instance declaration for ‘Monad (Writer String)’

这是我的代码:

newtype Writer log a = Writer {runWriter :: (a,log)} 
instance Monad (Writer String) where
  return a = Writer (a, "")
  ma >>= k …