head takes a list and returns its head. The head of a list is basically its first element.(提取第一个元素) ghci> head [5,4,3,2,1] 5 tail takes a list and returns its tail. In other words, it chops off a list's head.(
Haskell thinks of Strings as a list of characters, which is what[Char]means. We'll get to that later. True and False correspond to theBooltype, just like we'd expect. The'a'character is a singleChar. Our numbers are a little more complicated. Ignore theNumandFractionalwords for now. ...
是世界通用的条形码。EAN13码是由前缀码、厂商识别码、商品项目代码和校验码组成，总共13位数字。他的编...
K = random:uniform(N) - 1, Ek = array:get(K, Array), En = array:get(N, Array), shuffle(array:set(K, En, array:set(N, Ek, Array)), N-1). jpalecek 的area of a polygon例子: def area(figure : List[Point]) : Float = { if(figure.empty) return 0 val last = figure(0)...
在线运⾏ main=do let x=[1..10] putStrLn Our list is: print (x) putStrLn The last element of our list is: print (last x) 它将产⽣以下输出- Our list is: [1,2,3,4,5,6,7,8,9,10] The last element of our list is: 10 初始函数 吾⽣也有涯,⽽知⽆涯 - ⽆涯教程...
Current element: 1 Enter Return, q or the replacement value:Current element: 2 Enter Return, q or the replacement value:Current element: 6 Enter Return, q or the replacement value: 42 Current element: 24 Enter Return, q or the replacement value: q Done: fromList [(1,1),(2,2),(3,...
Get submatch indices-- match of __entire__ regex is first element, not first capture -- can also return Data.Array instead of List getAllSubmatches (a =~ b) :: [(Int, Int)] -- (index, length) λ> getAllSubmatches ("div[attr=1234]" =~ "div\\[([a-z]+)=([^]]+)\\]"...
What do you think is the type of the head function? Because head takes a list of any type and returns the first element, so what could it be? Let's check! ghci> :t head head :: [a] -> a Hmmm! What is this a? Is it a type? Remember that we previously stated that types ...
-- Having code split up into several modules has quite a lot of advantages. If a module is generic enough, the functions it exports can be used in a multitude of different programs. -- which is by default import Data.List numUniques :: (Eq a)=> [a] -> Int ...
0suggestshead xas a "suggestion" severity hint. Typicallyheadis a simpler way of expressing the first element of a list, especially if you are treating the list inductively. However, in the expressionf (x !! 4) (x !! 0) (x !! 7), replacing the middle argument withheadmakes it harde...