Haskell如何将整数转换为不同的类型？

fromIntegral :: (Integral a, Num b) => a -> b

main = do
    let numInt = 42 :: Int
    let numFloat = fromIntegral numInt :: Float
    let numDouble = fromIntegral numInt :: Double
    print (numFloat, numDouble) -- 输出：(42.0,42.0)

toInteger :: Integral a => a -> Integer

main = do
    let numInt = 42 :: Int
    let numInteger = toInteger numInt :: Integer
    print numInteger -- 输出：42

main = do
    let numInt = 42 :: Int
    let numFloat = numInt :: Float -- 不建议这样做，可能导致数据丢失
    print numFloat -- 输出：42.0