Chapter 7: Modules

Chapter 7: Modules

1. Data.List

   • The Prelude module exports some functions from Data.List for convenience
   • It provides some very useful functions for dealing with lists.
   • You don't have to import Data.List via a qualified import because it doesn't clash with any Prelude names

2. Load Moduies

   • You can choose to import all the module or only some functions
   • Import quialified allows you to differantiate functions with the same name putting the module name before the funciton
   • All the functions that the module exports become available in the global namespace
   • The syntax for importing modules is import <import module name>

3. Data.Char

   • It exports functions that deal with characters
   • It's also helpful when filtering and mapping over strings because they're just lists of characters

4. Data.Map

   • Association lists (also called dictionaries) are lists that are used to store key-value pairs where ordering doesn't matter
   • Offers association lists that are much faster (because they're internally implemented with trees) and also it provides a lot of utility functions
   • exports functions that clash with the Prelude and Data.List ones, we'll do a qualified import.

5. Dta.Set

   • They're internally implemented with trees
   • All the elements in a set are unique
   • clash with a lot of Prelude and Data.List names, we do a qualified import.
   • The most common operation when dealing with sets are inserting into a set, checking for membership and converting a set to a list

6. Making our own modules

   • The name of the file .hs needs to be the name of the module
   • After creating the file we need to specify the functions that it exports
   • After specifing the funtions we put a where and define the functions
   • export only those functions that act as a sort of interface to our module so that the implementation is hidden
   • Ffunctions that serve some common purpose you can put them in their own module.