Question

编程 haskell ——编写一个显示放大字符串的函数，如图

我编写的一部分程序如下，不过运行有误
sayit :: String -> IO ()
sayit (x :xs) = putStr (sideByside (x : xs))

sideByside :: String -> String
sideByside [ ] = [ ]
sideByside (x : xs) = x ++ sideByside xs
a :: [String]
a = [
" A ",
" A A ",
" A A " ,
" A A ",
" A A A A A ",
" A A ",
" "
]
e :: [String]
e = [
"EEEEEEEE ",
"E ",
"E ",
"EEEEEEE ",
"E ",
"E ",
"EEEEEEEE "
]

Answer 1

没看懂你写的意思，就不改题目了
你的 x ++ sideByside xs中x是char类型 ++ 后面的是string类型，也就是[char]类型，++只能用在两个同类型的list上面，你根据你的思路改下吧

追问

似乎可以用map 和 foldr高阶函数去写程序