Functional Programming

 

[more to come]

Functional programming means calling that functions with some arguments. Those functions return a value, a list of values or multiple values. In most programming languages, function calls are done in the following way: function-name (argument1, argument2, ....)

Function calls often used in an embedded way, like outer-function(next-function(next-function(innermost-function(args)))) Here is a imaginary example:

  display-nicely
     (sort-list
            (retrieve-all-players(player-data-base, guest-data-base)
            :how alphabetically)
      )

Functional programming style is useful in several situations, e.g.

• When you want to implement filters, i.e. procedures that that transform data into temporary data-structures you need for some job.
• In complex ``systems'' where the application layer allows application programmers to specify how certain operations on certain objects are to be done. A good example is TECFA's WWW interface. E.g. a function like :htext has the task to return a list of ``good'' html which then can be dumped back to a www client by another procedure. And you can define your own :htext for any MOO object you own.

It is possible to mix functional and procedural and object oriented programming style. However this is not always a good idea. Ideally procedures ``sold'' as functions should just return a value and NOT modify permanent data-structures. This way others and even you can use your functions and *just* expect that they will take some data, do something with them and return the result back to your procedure for for further use.

If functions do alter data somewhere, you have to document that somewhere.