;Sayings
friendly := ["hello there!", "Howdy!", "Greetings friend!", "hi there"]
helpful := ["x next to y and z", "this is helpful", "The sky is blue"]
other := ["where is my toaster", "do it", "ju
对函数参数进行约束的最佳做法是什么? 类似于一个检查对数函数内部的检查负数: SELECT log(-1, 1)
抛出错误: [2201E] ERROR: cannot take logarithm of a negative number
到目前为止,我发现了一个办法做到这一点使用PL/pgSQL的函数体内部,但它对我来说不是一个好的解决方案。 有没有办法在函数声明中进行约束? 我希望看
此功能的签名令我困惑,所有在线信息让我感到困惑。有人可以向我解释功能的签名,也许给我一个例子吗? sort3 :: Ord a => (a -> a -> Ordering) -> [a] -> [a]
sort3 cmp xs | length(xs) < 1 = xs
这是我得到的错误。 Couldn't match expected type ‘a -> a -> Ordering’
所以我有这个功能 intCMP :: Int -> Int -> Ordering
intCMP a b | a == b =EQ
| a < b = LT
| otherwise = GT
和定义 xs = [1,2,3]
我试图找到有关该列表的信息,但我有troouble传球元素融入intCMP 这此列表是我想要做的 intCMP head(xs) 1