using Haskell programming solve the question given the below.

Q : Write a function isNumber :: String -> Bool that tests if a string contains a valid number. A valid number is defined in EBNF as: number ! :digit+ j digit+ [ :digit?] For example,.5, 1.5, 1, 1. are all valid numbers. As usual, + signifies one or more occurrences, and * denotes zero or more. You may use the isDigit function from the Data.Char module.

Hint: you may wish to write functions someDigits, manyDigits :: String -> Bool to test for :digit+ and digit?.