haskell - 警告: Pattern match is redundant?是什么原因

Question

我正在尝试解决将华氏温度转换为摄氏温度的练习​​，反之亦然，但我收到此警告:

Pattern match is redundant
In an equation for ‘tempToC’: tempToC temp = ...compile(-Woverlapping-patterns)

我是 Haskell 的新手，需要帮助来理解警告的原因。

module Temperature (tempToC, tempToF) where

{- Implement the function `tempToC` to convert
`  Fahrenheit to Celsius                    -}

tempToC :: Integer -> Float
tempToC temp = error "Implement this function."
tempToC temp = fromIntegral (temp - 32 ) / 1.8 --line of the warning

{- Implement the function `tempToF` to convert
   Celsius to Fahrenheit                    -}

tempToF :: Float -> Integer
tempToF temp = error "Implement this function."
tempToF temp = ceiling  (temp * 1.8 + 32) --line of the warning

Answer 1

您需要删除行 tempToC temp = error "Implement this function." 和 tempToF temp = error "Implement this function."。由于 temp 只是命名一个新变量，它将匹配任何内容，因此这些行将阻止它们下面的行运行。