CSC302 2007S, Class 34: Declarative Langauges

Admin:
* When does each group want to present?
* EC for attending today's Quantitative Sociology talk.
* Handout: SEQUEL
  * For Friday

Overview:
* Language Paradigms, Revisited.
* Abstraction, Revisited.
* Common Categories of Declarative Languages.
  * Predicate Logic Languages.
  * Regular Expression Languages.
  * Database Languages.

/Language Paradigms/

* Traditional classification
  * Imperative - Command based
    * Algorithms/programs expressed as sequences of commands
    * Emphasis: Focus on how to sequence (goto, control structures)
    * Emphasis: What kinds of commands (von Neumann - Data movement)
  * Object-Oriented
    * Algorithms/programs expressed as a collection of communicating objects
      * An object groups data and methods/messages that operate on those data
    * Expectation: Inheritance, Polymorphism, Encapsulation
  * (Functional)
    * Algorithms/programs expressed as definition and application of functions
    * Expectation: Lists, symbolic data type, higher-order procedures, gc
    * Detour: What's the difference between functional and imperative, given that we define and apply functions in imperative languages, too?
      * More likely to be able to do higher-order programming in functional than in imperative
      * Functional programs less likely to involve side effects
        * Pure functional programming has none


  * Declarative - Declaration based
    * Algorithms/programs expressed as