Modules

Modules

1. A Haskell module is a collection of related functions, types and typeclasses. A Haskell program is a collection of modules where the main module loads up the other modules and then uses the functions defined in them to do something.

2. import Data.List

3. Data.List

   • "intersperse" takes an element and a list and then puts that element in between each pair of elements in the list. Here's a demonstration:
   • "transpose" transposes a list of lists. If you look at a list of lists as a 2D matrix, the columns become the rows and vice versa.
   • "splitAt" takes a number and a list. It then splits the list at that many elements, returning the resulting two lists in a tuple.
   • "dropWhile" is similar, only it drops all the elements while the predicate is true. Once predicate equates to False, it returns the rest of the list. An extremely useful and lovely function!

4. Data.Char

   • "isControl" checks whether a character is a control character.
   • "isLower" checks whether a character is lower-cased.
   • "isDigit" checks whether a character is a digit.
   • "isLetter" checks whether a character is a letter.

5. Data.Set

   • The "fromList" function works much like you would expect. It takes a list and converts it into a set.
   • the "difference" function to see which letters are in the first set but aren't in the second one and vice versa.

6. import qualified Directory.Module as NewName

7. module Directory.Module ( function , function ) where