ITEC 380

Organization of programming languages

Dr. Andrew Ray

Introduction

Objectives

• Introductions (Me + You)• Outline of course• Why study languages? • Paradigms• How languages are understood

Introduction

Me

• 6th year here at RU• 1st time teaching this course• Have used lessons from this type of

course to help with– Research– Teaching

Introduction

You

• What is one topic you’d really like to learn about concerning programming languages?

• What do you want to learn in this class?

• How interested are you in this class? (1-10)

• Share with class

Introduction

How?

• Synchronous component• Study at your leisure lectures• Self study / experimentation• Homework assignments– Intro–Major project

• Adaptability– Online forums/chat/twitter?

Introduction

Information

• Course website– www.radford.edu/aaray/ITEC_380

• Demo

Introduction

Outline of course

• 1-2 - Languages• 3-6 – Functional programming• 7-10 – Logical programming• 11-12 – Procedural programming• 13-14 – OO / Review

Introduction

Paradigms

• Radically different methods of accomplishing the same task

• Procedural• Object oriented• Functional• Logical

Introduction

Example

• Quicksort in haskell

quicksort :: Ord a => [a] -> [a] quicksort [] = [] quicksort (p:xs) = (quicksort lesser) ++ [p] ++ (quicksort greater)

where lesser = filter (< p) xs greater = filter (>= p) xs

Introduction

Examplevoid qsort(int a[], int lo, int hi) { int h, l, p, t; if (lo < hi) { l = lo; h = hi; p = a[hi]; do { while ((l < h) && (a[l] <= p)) l = l+1; while ((h > l) && (a[h] >= p)) h = h-1; if (l < h) { t = a[l]; a[l] = a[h]; a[h] = t; } } while (l < h); a[hi] = a[l]; a[l] = p; qsort( a, lo, l-1 ); qsort( a, l+1, hi ); }}

Introduction

Paradigms

• Right tool right job• OO is probably used for > 95% of

software development• Purpose– Performance– Reliability– Elegance– Expression

Introduction

Choose your language

• You are familiar with OO and procedural languages

• Goal: Not a rehash of Java / Ada• Desire: Choose a different OO &

procedural language to study for the course

• Thoughts?

Introduction

Languages

• What is the purpose of a language?• Why are there multiple languages?• What are the major components of

languages?

Introduction

Computers

• Syntax– Did you put the exact number of ;’s in

it?

• Semantics–What does it mean?

• Goal– Tell the computer what to do

Introduction

Implementation

• Compilation– Source, translation to binary, execution

• Interpretation– Source, intermediate program,

execution

• Benefits / downsides

Introduction

History

• Dr. Okie’s history notes– http://www.radford.edu/~nokie/classes/

380/w1l4.html

Introduction

Compilers

• How a language is understood (ears / brain)

• Lexical analysis• Syntactic Analysis• Intermediate code generation• Optimization• Code Generation• All use a central DB to store info

(symbol table)

Introduction

Symbol table

• Keystore method– Variables• Type, value, scope, memory location

– Functions– Classes

• Put info into table• Pull it out when generating code

Introduction

Stage 1

• Read the information• Start at the top left and read a

character at a time• When you hit whitespace/eos,

generate token• Hand token off• Repeat

What tokens come fromx = 12 + y * 34?

Introduction

Token handling

• Parse tree–What happens to each token

Token 1: xToken 2: =Token 3: 12Token 4: +Token 5: yToken 6: *Token 7: 34Token 8: ;

Tree

x =

12 +

y * 34

Introduction

Code generation

• Use parse tree / symbol table• Step 1 – Lookup y’s value• Step 2 – Multiply, store temp• Step 3 – Add 12 to temp,

store in temp2

• Step 4 – Assign temp2 to x• Not difficult to generate assembly for

this

x =

12 +

y * 34

Introduction

Optimization

• How to make your code better• Extremely difficult field• Reorganization of information– Unrolling loops

• Reduce redundant information

Introduction

Not universal

• Not every implementation follows these steps

• Linking result against existing code• Targeting interpreter versus

assembler

Introduction

Review

• Major paradigms / history of languages

• Parts of a computer language• How a language becomes real

Introduction

Next week

• Grammar• Variable types / bindings / lifetime