获得输入到Netwire程序 [英] Getting input into Netwire programs

问题描述

我没有问题写所有的电线，我想将输入转换为输出。

现在是编写IO包装以配合我的真实世界输入的时候了，我有点困惑。

我应该为 Wire semab 的 s 参数创建一个自定义会话类型，并将我的传感器值嵌入如果是这样，我有这些问题：

1. 这是怎么回事 class（Monoid s，Real t）=>的 Monoid s HasTime t s | s - >吨？它用于什么？


2. 我正在考虑在传感器读数上加上 Map String Double ，但我的monoid紧缩字典？它应该是左偏吗？右侧偏置？以上都不是？

如果不是，我该怎么办？我想以形式的连线为一些 s 结束Wire的InhibitionReason Identity（）Double ，表示我的输入。

这是我的理解，我不想或不需要使用 m 参数 Wire 用于此目的，从而允许电线本身是纯粹的，并将IO限制在逐步通过顶层线路的代码中。这是不正确的？

解决方案

将数据放入 Wire semab 通过输入 a 。可以通过使用 WPure 或 WGen 来获取状态变量delta s 或底层 Monad m ，但这些让我们远离主要抽象。主要抽象为 Arrow 和 Category ，它们只知道 ab ，而不是大约 sem 。

下面是一个非常简单的程序的例子，提供输入作为输入 A 。 double 是程序的最外层。 repl 是一个小型的read-eval-print循环，它调用 stepWire 来运行线。

  import FRP.Netwire 
 import Control.Wire.Core 
 
 import Prelude hiding（id，（。）） 
 
 double :: Arrow a => a [x] [x] 
 double = arr（\ xs  - > xs ++ xs）
 
 repl :: Wire（Timed Int（））e IO String String  - > ; IO（）
 repl w = do 
 a<  -  getLine 
（eb，w'）< -  stepWire w（Timed 1（））（Right a）
 putStrLn。 （constInhibited）id $ eb 
 repl w'
 
 main = repl double 
  

请注意，我们将时差传递给 stepWire ，而不是总时间。我们可以通过运行不同的顶级线程来检查这是否正确。

  timeString ::（HasTime ts ，Show t，Monad m）=> Wire是一个String 
 timeString = arr节目。时间
 
 main = repl timeString 
  

具有所需的输出： p>

  a 
 1 
b 
 2 
c 
 3 
  

I'm getting started with Netwire version 5.

I have no problem writing all the wires I want to transform my inputs into my outputs.

Now the time has come to write the IO wrapper to tie in my real-world inputs, and I am a bit confused.

Am I supposed to create a custom session type for the s parameter of Wire s e m a b and embed my sensor values in there?

If so, I have these questions:

1. What's up with the Monoid s context of class (Monoid s, Real t) => HasTime t s | s -> t? What is it used for?
2. I was thinking of tacking on a Map String Double with my sensor readings, but how should my monoid crunch the dictionaries? Should it be left-biased? Right-biased? None of the above?

If not, what am I supposed to do? I want to end up with wires of the form Wire s InhibitionReason Identity () Double for some s, representing my input.

It's my understanding that I don't want or need to use the monadic m parameter of Wire for this purpose, allowing the wires themselves to be pure and confining the IO to the code that steps through the top-level wire(s). Is this incorrect?

解决方案

The simplest way to put data into a Wire s e m a b is via the input a. It's possible, through the use of WPure or WGen to get data out of the state delta s or the underlying Monad m, but these take us further away from the main abstractions. The main abstractions are Arrow and Category, which only know about a b, and not about s e m.

Here's an example of a very simple program, providing input as the input a. double is the outermost wire of the program. repl is a small read-eval-print loop that calls stepWire to run the wire.

import FRP.Netwire
import Control.Wire.Core

import Prelude hiding (id, (.))

double :: Arrow a => a [x] [x]
double = arr (\xs -> xs ++ xs)

repl :: Wire (Timed Int ()) e IO String String -> IO ()
repl w = do
    a <- getLine
    (eb, w') <- stepWire w (Timed 1 ()) (Right a)
    putStrLn . either (const "Inhibited") id $ eb
    repl w'

main = repl double

Notice that we pass in the time difference to stepWire, not the total elapsed time. We can check that this is the correct thing to do by running a different top-level wire.

timeString :: (HasTime t s, Show t, Monad m) => Wire s e m a String
timeString = arr show . time

main = repl timeString 

Which has the desired output:

a
1
b
2
c
3

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