在此功能的Cardano定义中使用的语法是什么？

Question

如何解释此功能：

friendlyValidityRange
  :: CardanoEra era
  -> (TxValidityLowerBound era, TxValidityUpperBound era)
  -> Aeson.Value
friendlyValidityRange era = \case
  ShelleyTtl ttl -> object ["time to live" .= ttl]
  (lowerBound, upperBound)
    | isLowerBoundSupported || isUpperBoundSupported ->
        object
          [ ...
          ]
    | otherwise -> Null
 where
  isLowerBoundSupported = isJust $ validityLowerBoundSupportedInEra era
  isUpperBoundSupported = isJust $ validityUpperBoundSupportedInEra era

我认为 friendlyvalityrange 函数使用部分函数概念概念，但仍然无法理解它。 friendlyValityRange 's era and （下部，上行）参数以这样的分离方式传递？

我尝试模仿它使用“遵循演示”，但仍无法完成。

module Main where

data Age = Child | Adult

-- Function that accept two agrs: Age, (weightMin, weightMax) , and return health description string
weightAnalyse :: Age -> (Int, Int) -> String
weightAnalyse age = \case
    Child    ->  ?  -- how to comsume the (min, max) tuple
    Adult    ->  ? 
    
main :: IO ()
main = do
  weightAnalyse Child (30, 60)
  weightAnalyse Adult (60, 130)

Answer 1

您缺少 nofollow noreferrer“>模式同步。 Take a look at 第105行

{-# LANGUAGE PatternSynonyms #-}

pattern ShelleyTtl
  :: SlotNo -> (TxValidityLowerBound era, TxValidityUpperBound era)
pattern ShelleyTtl ttl <-
  ( TxValidityNoLowerBound
  , TxValidityUpperBound ValidityUpperBoundInShelleyEra ttl
  )

这说明了第一个组件为 txvalitynolowerbound code> txvalityuperperbound velityuperityupersupersupertiupipperboundinshelleyera ttlleyera ttl 模式 shelleyttl ttl 带有 ttl 绑定到正确的值。

因此， shelleyttl ttl 在

friendlyValidityRange era = \case
  ShelleyTtl ttl -> object ["time to live" .= ttl]

匹配特定类型的元组中！

您的 weighanalyse 实际上与您所引用的示例不匹配，但会按照以下方式进行：

{-# LANGUAGE LambdaCase, PatternSynonyms  #-}

data Age = Child String | Adult

pattern ChildPattern x <- (_, Child x)

weightAnalyse :: Int -> (Int, Age) -> String
weightAnalyse id = \case
  ChildPattern x -> x
  (a, age) -> "other"
-- The parameter id is unused and could be removed but is kept
-- to match the original version of the function.

--  *> weightAnalyse 1 (30, Child "foo")
-- "foo"
--  *> weightAnalyse 2 (60, Adult)
-- "other"