CSC302 2006S, Class 1: About the Class

Admin:
* Course Site:
  http://www.cs.grinnell.edu/~rebelsky/Courses/CS302/2006S/
* Readings distributed
* Book not needed for a few weeks
* Warning! Sam's pedagogical approach is R^4: Rebelsky round-robin recitation
* Short Survey

Overview:
* What is a programming language?
* Why study programming languages?
* How should we study 'em?
* Course details

/Short Survey/

* Goal: Give me some sense of what you do and don't know
* Scheme topics
  * Continuations? 0
  * Closures? 0
  * Macros? 0
    In general, a macro provides a shorthand for longer pieces of code
  * Currying? 2, maybe
* Java topics
  * Generics (parameterized classes)? 0
  * Anonymous Inner Classes 0
  * Reflection 0
* Other languages
  * SQL? About 1/2
  * C? Everyone, but not true C hackers
  while (*c++ = *d++) ;
  * C++? About 1/2
  * C#? 1
  * Ruby? 0
  * Smalltalk? 0
  * Prolog? 0

What is a programming language?
* Syntactic and semantic systems that permits you to represent functions and ... Maybe
* A standardized communication technique for describing instructions to a computer [Wikipedia, 2006]
  * Syntax describes how you communicate
  * Semantics describes what it means
  * Sam's correction: "Communicate with computer *or human*"
  * Sam's next correction: Communicate *algorithms*

Why study programming languages?
Why are you here?
Why does Grinnell require CSC302?
* A major subdiscipline of CS; you should know the ideas
* Let students learn other languages
* Help students understand similarities and differences
* Psychotic
* Reinforce principles
* Historical aspect: "Those who forget history are doomed to repeat it"; "Those who forget history are doomed to rewrite Cobol or Fortran 1"; To help predict the future
* Recaps many courses (including compilers)
* Since we use them, some understanding of how they function might be helpful (although that's more a topic for compilers)
* Compare and contrast: Advantages, efficiencies, etc.
* Most large systems involve their own languages

How do we study languages?
* Language of the week (some of that)
* Explicitly address design principles (some of that)
* Implement (little of that)
* History of Programming languages: Learn about contexts!
* We will do a combination!

What kinds of languages are there? (Key language paradigms)
* Imperative (Fortran, Pascal, C, ...)
  Algorithms expressed as sequences of basic operations, which
  include data movement (assignment, I/O) and arithmetic.
* Functional (LISP, Scheme, FP, Haskell, ...)
  Algorithms expressed by function definition and application, including functions as first-class data

Traditional imperative/functional contrast: inner product

int sum = 0;
for (int i = 0; i < n; i++) {
  sum += A[i]*B[i];
}

(apply + (map * A B))

* Object-Oriented (Simula, Smalltalk, C++, Java, Ruby, ...)
  Algorithms expressed in terms of communicating objects
  Lots of focus on how you describe objects: Inheritance,
    Polymorphism, Encapsulation
* Declarative (Prolog, SQL, All functional languages ...)
  Algorithms expressed in terms of "facts"; No or little explicit control
  Regular expressions are a good everyday declarative language

* Dave's observation: These overlap somewhat; 
* Sam's response: When we talk about a language, we look at its key focus