问题
I would like to print a char underlining a String n times, with n the length of the String in Haskell.
How should I do this?
My String is: "Available Chars (x)" and I want to have a char underlining that sentence, which should have exactly the same length as the "Available Chars (x)". But x is an int, so it could be "1" or "10" or "1000" etc.. so the length is variable. I got the length but i didnt know how to print that char as long as the string is...
回答1:
Use replicate:
underline :: String -> String
underline = flip replicate '-' . length
This will give you a string which is n times the character '-' where n is the length of the input string. It is the same as:
underline = map $ const '-'
You can then use it like this (if for example yourString = "Available Chars (111)"):
> putStrLn yourString >> putStrLn (underline yourString)
Available Chars (111)
---------------------
回答2:
got it!
replicate n 'charHere'
for example, if you want to repeat the char '-' 12 times:
replicate 12 '-'
回答3:
A possibility is to (re)implement replicate, for instance as follows,
replicate' :: Int -> a -> [a]
replicate' n x = if (n <= 0) then [] else (x : replicate (n-1) x)
来源：https://stackoverflow.com/questions/26618059/how-to-print-the-same-char-n-times-in-haskell