CSC302 2005S, Class 1: Introduction

Overview:
* Warning! Participation ahead
* What is a programming language?
* Why study programming languages?
* How to study programming languages?
* This class
* Expectations
* Other stuff

Preliminaries
* Sam calls on people *a lot*
* These notes available online
* Take your own notes
* Web site note quite ready

What is a programming language?
* Steve: A series of statements used to take in certain preconditions and with the desired postconditions
* John translates: 
  * "Series of statements" = "Lines of code"
  * "Preconditions" = "Things we already know or hold true"
  * "Postconditions" = "Things we want to accomplish"
* Ben suggests that we've just described a program; the language is more what you use to write the program.
* Ben: A language is something used to write programs
* Cassandra: Missing some aspects
* Cassandra: A method for communicating instructions to the computer
* Gene: A tool that the computer can execute to perform some task

Detour: What is computer science?
* The study of ALGORITHMS and DATA
* The study of PROBLEM SOLVING

Refining Cassie's definitions
* Omondi replaces "stuff" with "ALGORITHMS and DATA"
* Revised: A method for communicating ALGORITHMS and DATA to the computer
* Mark suggests sometimes we communicate with people
(define map
  (lambda (fun lst)
    (if (null? lst) null
        (cons (fun (car lst) (map fun (cdr lst)))))))
Map is a function of two parameters, a function, fun, and a list, lst.
Map creates a new list by applying fun to each element of lst.
* Revised: A method for communicating ALGORITHMS and DATA (to computers or people or both)
* Arjun: "Language" would be better than "method", but that's circular.
* A language is a group of symbols, grammatical rules, and semantic rules for expressing something

What does it mean to study programming languages?
* Learn a lot.
* Study common and uncommon design issues
* Historical perspective
* Design our own
* Implement one or more languages

Focus of CSC302
* Study common and uncommon design issues
* Learn "a lot": 
  * Languages you should already know: Scheme, Java, C
  * Languages you probably don't know: FP, Haskell, Smalltalk, Prolog
* "Primary literature" study

Our goal is to study these things this semester.  Why?
* It's required.  (Why do we require it?)
* Josh is here because he's trying to write a language for Plans ([Yellow Tail])
* Graduate departments expect it.  (Why do departments expect PL?)
* Different languages provide different ways to think about writing algorithms and organizing data.  Learning different languages gives you broader thinking skills.
* Josh2 agrees with Daren.

* By learning more about the tools we use, we become better at using them
* Evidence suggests that most large programs include their own language
* Knowing more about languages helps you find the best language for a taks

Why did Josh have to buy Gries?
* Important to learn how to formally define the statements in a language
* Important to learn how to "prove" a program is correct
* Formal methods are good