.. include:: <s5defs.txt>

=============================
Dynamic Programming Languages
=============================


What this course is about
-------------------------

Getting a feel for dynamic languages:

* What a dynamic language is

* When and how they are practical

* Learn Python and see other languages


Overview
--------

A dynamic language is a language with:

* Dynamic typing

* Most things changeable at run-time

* Reflection

* "Late-Bound Everything"


Overview (2)
------------

In practice, dynamic languages are often:

* Interactive

* Garbage-Collected

* Interpreted (and slower)

* "Everything is an Object"


Interactivity
-----------------

Interactivity:

* Type and immediately execute parts of programs


Dynamic Typing
-----------------

Dynamic Typing:

* Types not declared in the source code

* Types attached to values at run-time


Garbage-Collected
-------------------

Garbage-Collected:

* No manual memory management


"Late-Bound Everything"
---------------------------

Late Binding:

* The object that a variable name references
  can only be determined at run-time


"Everything is an Object"
------------------------------

Everything is an Object:

* Numbers, Functions, Classes, their Instances,
  Lists, Modules, etc.

* All objects are manipulated in the same way


Changeable at run-time
--------------------------------------

Most things changeable at run-time, e.g.:

* The bindings

* All objects (classes, methods, modules...)


Reflection
---------------

Reflection:

* The way in which we can inspect (and change) the
  running program from within itself


Pros and Cons
---------------------------------------------------------

Pros and Cons of Dynamic versus non-Dynamic languages:


Pros and Cons
---------------------------------------------------------

...No kind of programming language is inherently better
or worse

* It's about the "right tool for the right job"

* We will come back to Pros and Cons


Examples
----------------

Dynamic languages (exercice: why?):

* Python

* Prolog

* Ruby, Perl, Smalltalk, Lisp, Scheme, JavaScript, Lua, Self...


Anti-Examples
-------------------

Non-dynamic languages (exercice: why?):

* C

* Java (but getting there)

* Assembler

* Haskell, C++, Ada, ML, Pascal, Fortran, Cobol...


End
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