是否可以创建一个计算指令数量的Monad? [英] Is it possible to create a Monad that count the number of instructions?

问题描述

考虑到monad，我想到了monad作为打破冯·诺依曼(Von Neumann)体系结构的方式的想法.冯·诺依曼体系结构使用一组指令(称为程序)来更改内存中的数据，并且该程序的每条指令的执行都会更新程序计数器，以了解下一条指令将要执行.

Thinking about monad, it came to me the idea of a monad as the way to break with the Von Neumann architecture. The Von Neumann architecture uses a set of instructions (called program) to change the data in memory and the execution of each instruction of the program updates a program counter to know whom instruction is the next to execute.

如果我们将冯·诺依曼(Von Neumann)架构视为monad，则绑定运算符(>> =)将更新程序计数器.我们可以制造出打破冯·诺依曼(Von Neumann)架构的Monad，从而在绑定中做更多的事情.例如，我们可以有一个Monad来计数程序中执行的指令数.

If we think about the Von Neumann architecture as a monad, the bind operator (>>=) update the program counter. We can make a Monad that break Von Neumann architecture to do more in the bind. As an example, we can have a Monad that count the number of instructions executed in our programs.

但是，当我尝试在haskell中将Monad实现为:

But, when I tried to implement that Monad in haskell as:

data Counter a = Counter Integer a
             deriving( Show )

instance Monad Counter where
  (Counter n1 a) >>= f = let Counter _ b = f a
                     in (Counter (n1+1) b)
  return a = Counter 1 a

我注意到这将违反Monads法律，例如:

I notice it'll break de Monads laws, e.g:

return x >>= f            /=   f x

do
   a <- return 3
   return a

do 
   return 3

由于monad定律，这两个块是相同的，但是由于它们具有不同数量的指令(句子)，它们将返回不同的内容

The two blocks are the same because the monad laws, but they'll return something different because they have different number of instructions (sentences)

我做错什么了吗?还是不可能有这种单子?

Do I made something wrong? or Is it not possible to have such Monad?

推荐答案

严格来说，任何此类单子"都违反了单子法则，因此...不是单子.有关详细信息，请参见此上一个问题.换句话说-您的猜测是正确的，不可能有这样的单子.

Strictly speaking, any such "monad" breaks the monad laws and is thus... not a monad. See this previous question for details. In other words - your guess is correct, it is not possible to have such a monad.

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