Note : Complete the following Haskell function definitions. Unless stated otherwise do not use library functions that are not in the Haskell standard prelude. Use the specified function name as your code will be tested by a Haskell function expecting that function name. The testing program may use many more test cases than the ones shown in the specification. So, please test your functions extensively to ensure that you maximise your marks.

Q : C) 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+ | 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? .