On Tue, Apr 10, 2018 at 08:47:17PM +0800, 清羽 wrote:
And May I ask what is the meaning of ch <= 'z' and 'a' <= ch? I copied this as a condition and solved the problem.here is my work. isLower :: Char -> Bool isLower x = if x ch <= 'z' && 'a' <= ch then True else False. Thanks in advance.
Hello 清羽, Char is an instance of Ord, so you can use <, compare, etc. with it. <= and >= stand for "less or equal than" and "greater or equal than". As with many enumeration types, the order is a bit arbitrary λ> minBound :: Char '\NUL' λ> maxBound :: Char '\1114111' λ> ['$'..'Z'] "$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ" -- so * will be < than, say, A λ> '*' < 'A' True Does that answer your question?