NUIM/CS351 Lecture 01 Notes

Module: CS351 (Programming Paradigms)
Lecturer: Barak Pearlmutter
Lecture No: 1

In this course we shall do some "old school programming"
We will be learning a programming language called Scheme (a weird but wonderful language)
This will help us move up the "Tower of Power"
We are also covering Prolog and Haskell

The Tower of Power

People below you don't know what they're missing.
People above you use strange hard-to-understand arcane constructs.
eg. Java Programmer looks down on a Fortran programmer because they can't see how a programmer can survive without objects and classes etc. The Fortran programmer can't see the need for classes and objects.
Java programmer doesn't see any benefit in a language like Haskell because they don't understand or see any need for the weird things it offers, like higher-order functions, lazy infinite streams, monads, type inference, etc.

One goal of this course is to get knowledge of other programming languages and paradigms, and to move up the "Tower of Power."

Implementation: DrScheme (part of the PLT Scheme software suite)

Scheme is:

Powerful
Simple but strange
Heavily based on lambda
Lambda replaces (in principle) many common control, data, and binding structures
easy to use to write compilers and interpreters
can understand many programming language constructs as syntactic sugar for underlying idiomatic usage of lambda
many modern compilers use lambda internally for this purpose

Note: during class when lambda is written on the board everybody must shout "The Power"!

() Parenthesis have two separate uses

Note: Parenthesis are not used for grouping in Scheme, as they are in Java.

Scheme	Java
(sin 1)	sin(1), or (((sin((1)))))
(+ 2 3)	2 + 3
(* 6 9)	69 or (((((6)))((9))))
(lambda (x) (+ x 1))	? (cannot easily write anonymous function)
(define add-one (lambda (x) (+ x 1)))	int addOne(int x){ return x+1); }
(if (< 2 2) 777 888)	(2 < 2) ? 777 : 888

Points taken off for comments in code!

;;; (factorial n)
;;; n!
;;; 0! = 1
;;; 1! = 1
;;; 2! = 2