冲突教程示例中 'pure' 关键字的用途是什么？

Question

在Clash官网上，有如下例子：

>>> sampleN @System 4 (register 0 (pure (8 :: Signed 8)))

我知道什么是纯函数，但为什么要在这里使用这个关键字？如果我删除它，我会得到一个错误：

Clash.Prelude> sampleN @System 4 (register 0 (8 :: Signed 8))

<interactive>:2:32: error:
    * Couldn't match expected type `Signal System a'
                  with actual type `Signed 8'
    * In the second argument of `register', namely `(8 :: Signed 8)'
      In the third argument of `sampleN', namely
        `(register 0 (8 :: Signed 8))'
      In the expression: sampleN @System 4 (register 0 (8 :: Signed 8))
    * Relevant bindings include it :: [a] (bound at <interactive>:2:1)

有线索吗？

Answer 1

Signal 具有 pure 所属的 Applicative 实例。 pure :: a -> Signal dom a 将类型 Signed 8 的值提升为 Signal dom (Signed 8)。在该上下文中与 Signal System a 结合导致 Signal System (Signed 8).

引用参考：http://hackage.haskell.org/package/clash-prelude-1.0.0/docs/Clash-Signal.html

冲突教程示例中 'pure' 关键字的用途是什么？

What is the purpose of 'pure' keyword in the clash tutorial example?

haskell

hdl

clash