CS5205: Foundation in Programming Languages Lecture 0 : Overview

1
CS5205 Foundation in Programming Languages
Lecture 0 Overview
Language Foundation, Extensions and Reasoning

Lecturer Chin Wei Ngan Email
chinwn_at_comp.nus.edu.sg Office COM2 4-32
2
Course Objectives
- graduate-level course with foundation focus
- languages as tools for programming -
foundations for reasoning about programs -
explore various language innovations
3
Course Outline

• Lecture Topics (13 weeks)
• Advanced Typed Language (Haskell)
• http//www.haskell.org
• Lambda Calculus (Core Language)
• Interpreters
• Untyped Scripting Language (Python)
• http//www.python.org
• Type System for Lightweight Analysis
• http//www.cs.cmu.edu/rwh/plbook/book.pdf
• Semantics

4
Administrative Matters
- mainly IVLE - Reading Materials (mostly
online) www.haskell.org Robert Harper
Foundations of Practical Programming Languages.
Free PL books http//freeprogrammi
ngbooks.com - Lectures Assignments Paper
Reading Exam - Assignment/Project (35) -
Paper Reading (10) - Quiz (10) - Exam (45)
5
Paper Presentation

• Focus on Language Innovation/Application
• Select A Paper (Week 2)
• Give Presentation (Week 4/5)
• Possible Topics
• Concurrent and MultiCore Programming
• Software Transaction Memory
• GUI Programming
• Testing with QuickCheck
• IDE for Haskell
• SELinks (OCaml)
• etc
• A List of Papers/Conferences will be given next
  week.

6
Assignments/Project (35)

• Small Exercises
• Mini-Project
• List of possible projects (Week 5)
• Your own project
• A useful tool
• Use advanced languages, such as
• Haskell, Ocaml, F, Python, Boo, etc
• Evaluation
• (i) presentation/demo
• (ii) draft report/paper

7
Why Study Foundations of PL?

• Language used to organize programming thoughts.
• Language can describe and organize computation.
• Language features affect how ideas are expressed.
• Foundation needed to support the design of good
  language features

8
Benefits of Good PL Features

• Readability
• Extensible Software.
• Modifiability.
• Reusability.
• Correctness.

9
Benefits of Studying Foundations of PL

• Design new languages for your work/research?
• Inside any successful software system is a PL
• Emacs Elisp
• Word, PPT VBScript
• Quake QuakeC
• Facebook FBML, FBJS
• Twitter Ruby on Rails/Scala
• Also Latex, XML, SQL, PS/PDF

10
Benefits of Studying Foundations of PL

• Different language paradigm can support different
  approaches to a given problem.
• Can choose a solution that is best (or good
  enough) for the given problem.
• PL is the primary tool of choice for programmers.
  If properly selected, it can amplify your
  programming capability.
• Era of domain-specific programming languages.

11
Many Dimensions of PL

• Syntax verbose vs succint. prefix vs distfix.
• Computational model functional, imperative, OO
  or constraint-based.
• Memory Model explicit deallocation, garbage
  collection or region-based.
• Typing static vs dynamic typing strong vs weak
  typing.
• Execution Model compiled (C/C), interpreted
  (Perl), hybrid (Java).
• Scoping static vs dynamic scoping.

12
Advanced Language - Haskell

• Strongly-typed with polymorphism
• Higher-order functions
• Pure Lazy Language.
• Algebraic data types records
• Exceptions
• Type classes, Monads, Arrows, etc
• Advantages concise, abstract, reuse
• Why use Haskell ?

13
Some Applications of FP/Haskell

• Hoogle search in code library
• Darcs distributed version control
• Programming user interface with arrows..
• How to program multicore?
• map/reduce and Cloud computing
• Bioinformatics
• Cryptography

14
Example - Haskell Program

• Apply a function to every element of a list.
• data List a Nil Cons a (List a)
• map f Nil Nil
• map f (Cons x xs) Cons (f x) (map f xs)

a type variable
map sqr(Cons 1 (Cons 2 (Cons 3 Nil))) gt
(Cons 1 (Cons 4 (Cons 9 Nil)))
15
Example - Haskell Program

• Built-in List Type with syntactic sugar
• data a aa
• map (a ? b) ? a ? b
• map f
• map f (xxs) (f x)(map f xs)

map sqr 1(2(3)) gt 1(4(9)) map sqr
1,2,3 gt 1,4,9
16
Paradigm Functional Expression

• Problem sum the square of a list of numbers
• sumsq 1,2,3,4 11 22 33 44.

• Problem sum the square of a list of numbers
• sumsq 0
• sumsq (xxs) (sqr x) (sumsq xs)

17
Paradigm Imperative Loop

• Problem sum the square of a list of numbers
• sumsq 1,2,3,4 11 22 33 44.

• In F (Ocaml dialect)
• sumsq Int Int
• sumsq xs let s ref 0 in
• for x in xs
• s !s x
• s

18
Paradigm Function-Level Composition

• Sum a list

sum 0 sum (xxs) x (sum xs)

• Square a list

square xs map sqr xs