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Cse321, Programming Languages and Compilers

18/21/2010

Lecture #1, Jan. 9, 2007Course Mechanics

Text Book

Down-loading SML

Syllabus - Course Overview

Entrance Exam

Standard MLThis weeks assignment

Top to bottom example

Lexical issues

Parsing and syntax issues

Translation issues

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Acknowledgements

The material taught in this course was madepossible by many people. Here is a partiallist:

Andrew Tolmach

Nathan Linger Harry Porter

Jinke Lee

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Todays AssignmentsReading

Engineering a Compiler Available In the PSU bookstore

Chapter 1, pp 1-26

There will be a 5 minute quiz on the reading Wednesday.

Search Find the class webpage

1 page programming Assignment Due Wednesday, Jan 10, 2007. In Just 2 Days!!

Login to some SML system. See how the system operates.Type in solutions (in a file) to the programming problems (InClass exercises 1 and 2 in this handout), load them into SML.Get them running, and print them out then turn them in onWednesday. What matters here is that you try out the SMLsystem, not that you get them perfect.

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Course Information CS321 - Languages and Compiler Design

Time: Monday & Wednesday 18:00-19:50 pm Place: PCAT 138

Instructor: Tim Sheard

office: room 115, CS Dept, 4th Ave Building, Portland State Univ.

phone: 503-725-2410 (work) 503-649-7242 (home)

office hours: Before class in my office (5:00-5:50), or by Appt.

Assignments Reading from text and handouts (quizzes on reading)

Daily, 1 page programming assignments

3 part programming project

Grading: midterm exam (25%)

3 parts of project (30%)

Daily 1 page assignments and quizzes (15%)

Final exam (30 %)

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Examinations

Entrance Exam. Do you know your REs and CFGs?

Quizzes on Reading Material. There is a possible quiz on every reading assignment

There will be a quiz on Wednesday!

Mid Term exam Wed. Feb 14, 2007. Time: in class.

Final exam Monday, Mar. 19, 2007. Time: 6:00-7:50.

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Text Book

Text: Engineering a Compiler Keith D. Cooper, and Linda Torczon

Other Reference Materials Auxilliary Material

Elements of Functional Programming (SML book)

by Chris Reade, Addison Wesley, ISBN 0-201-12915-9

Using the SML/NJ Systemhttp://www.cs.cmu.edu/~petel/smlguide/smlnj.htm

Class Handouts Each class, a copy of that days slides will be available as a

handout.

I will post files that contain the example programs used in eachlecture on the class web page

www.cs.pdx.edu/~sheard/course/Cs321

I will post Assignments there as well.

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Labs

Whenever you learn a new language its great to have

someone looking over your shoulder.

In this spirit I have scheduled some lab times wherepeople can work on learning ML while I am there tohelp. FAB INTEL Lab (FAB 55-17) downstairs by the Engineering and

Technology Manangements departmental offices

Friday Jan. 12, 2007. 4:00 5:30 PM

Tueday Jan. 16, 2007 4:00 5:30

Friday Jan. 19, 2005. 4:00 5:30 PM

Labs are not required, but attendance of at least oneis highly recommended!

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Installing SML

Software can be obtained at:

http://www.smlnj.org/ I am using the most recent version 110.60

but it displays the version 110.57 when it runs

Browse the documentation and Literature section of the SMLweb page. Find some resources that you can use.

SML also runs on the PSU linux and Intel labs linux

usepkg sml

then logout, or start a new shell

type: sm

Intel

In a commnd window

p:\programs\smlnj\addpkg.cmd

then logout, or start a new command window

then just type:

N:\>sml

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Entrance Exam

CS321 has some pretty serious prerequisites.

1. Write a regular expression for the set of strings thatbegins with an a which is followed by an arbitrarynumber of bs or cs, and is ended by a d.

e.g. ad, abbbd, abcbcbcd, etc.2. Transform your regular expression into a DFA

3. Write a context free grammar that recognizes thesame set of strings as your RE

4 Transform your CFG into a CFG that is left-recursionfree.

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Academic Integrity

Students are expected to be honest in their academicdealings. Dishonesty is dealt with severely.

Homework. Pass in only your own work.

Program assignments. Program independently. Examinations. Notes and such, only as each instructor allows.

OK to discuss how to solve

problems with other students,

but each student should

write up, debug, and turn in his

own solution.

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Course Thesis This course is about programming languages. We

study languages in two ways. From the perspective of the user

From the perspective of the implementer (compiler writer)

We will learn about some languages you may neverhave heard of. We will learn to program in one of

them (Standard ML). Its good to learn a newlanguage in depth.

This course is also about programming. There willbe extensive programming assignments in SML. Ifyou dont do them - you wont learn Youre deluding yourself if you think you can learn the material

without doing the exercises!

We will write a comiler for a Java subset. Its good tounderstand the implementation details of a languageyou already know.

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This course is all about programming

What makes a good program?

Write at least 3 things on a piece of paper.

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Standard ML

In this course we will use an implementation of the

language Standard ML

The SML/NJ Homepage has lots of usefulinformation: http://www.smlnj.org//

You can get a version to install on your ownmachine there.

I will use the version 110.57 or 110.60 of SML. Earlier versions probably

will work as well. I dont foresee any problems with other versions, butif you want to use the identical version that I use in class then this isthe one.

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Characteristics of SML

Applicative style input output description of problem.

First class functions pass as parameters

return as value of a function

store in data-structures

Less Importantly: Automatic memory management (G.C. no new or malloc)

Use of a strong type system which uses type inference, i.e. nodeclarations but still strongly typed.

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Syntactic Elements

Identifiers start with a letter followed by digits orother letters or primes or underscores. Valid Examples: a a3 ab aF

Invalid Examples: 12A

Identifiers can also be constructed with a sequenceof operators like: !@#$%^&*+~

Reserved words include fun val datatype if then else

if of let in end type

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Interacting

The normal style for interaction is to start SML, andthen type definitions into the window.

Types of commands 4+ 5;

val x = 34;

fun f x = x + 1;

Here are two commands you might find useful.

val pwd = OS.FileSys.getDir;

val cd = OS.FileSys.chDir;

To load a file that has a sml program type

Use file.sml;

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The SML Read-Typecheck-Eval-Print Loop

Standard ML of New Jersey v110.57 [built: Mon Nov 21 21:46:28 2005]

-- 3+5;

val it = 8 : int

-

- print "Hi there\n";

Hi there

val it = () : unit

-- val x = 22;

val x = 22 : int

-

- x+ 5;

val it = 27 : int

-

-val pwd = OS.FileSys.getDir;-val pwd = fn : unit -> string

- val cd = OS.FileSys.chDir;

val cd = fn : string -> unit

-

Note the semicolon when

youre ready to evaluate.

Otherwise commands can

spread across several lines.

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fun lastone x = hd (rev x)

fun prefix x = rev (tl (rev x))

In Class Exercise 1 Define prefix and lastone in terms of head tail and reverse.

First make a file S01code.sml Start sml

Change directory to

where the file resides

Load the file ( use S01code.html )

Test the function

Standard ML of New Jersey v110.57 - K;

- val cd = OS.FileSys.chDir;

val cd = fn : string -> unit

- cd "D:/work/sheard/courses/PsuCs321/web/notes";

- use "S01code.html";

[opening S01code.html]

val lastone = fn : 'a list -> 'aval prefix = fn : 'a list -> 'a list

val it = () : unit

- lastone [1,2,3,4];

val it = 4 : int

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In Class Exercise 2

define map and filter functions mymap f [1,2,3] = [f 1, f 2, f 3]

filter even [1,2,3,4,5] = [2,4]

fun mymap f [] = []

| mymap f (x::xs) = (f x)::(mymap f xs);

fun filter p [] = []

| filter p (x::xs) =

if (p x) then x::(filter p xs) else (filter p xs);

Sample Session

- mymap plusone [2,3,4]

[3, 4, 5]

- filter even [1,2,3,4,5,6]

[2, 4, 6]

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Course topics

Programming Language

Types of languages Data types and languages

Types and languages

Compilers Lexical analysis

Parsing Translation to abstract syntax using modern parser generator

technology.

Type checking

identifiers and symbol table organization,

Next Quarter in the second class of the sequence Intermediate representations

Backend analysis

Transformations and optimizations for a number of different kindsof languages

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Multi Pass Compilers

Passes

text

tokens

syntax trees

intermediate forms

(three address code, CPS code, etc)

assembly code machine code

Each phase is from one form to another, OR fromone form to the same form, which is often called asource to source transformation.

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The Top to Bottom Example

text:

tokens:

syntax tree:

id(z) eql id(x) plus id(pi) times float(12.0)

z = x + pi * 12.0

+Id(z)

float(12.0)

=

Id(z)

*Id(x)

Id(pi)

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Passes (cont)

Three address code:

temp1 := pi * 12.0

z := x * temp1

Assembly level code:

ld r1,x

ld r2,pi

add r1,r2

ldi r2,12.0 mul r1,r2

st r1,z

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Lexical Analysis

Produces Tokens and Deals with: white space

comments

reserved word identification

symbol table interface

Tokens are the terminals of grammars.

Lexical analysis reads the whole program, characterby character thus it needs to be efficient. This

implies fancy buffering techniques etc. Modernlexical generators handle these problems so we willignore them.

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Tokens, Patterns & Lexemes

Many strings from the input may produce the same

TOKEN i.e. identifiers, integers constants, floats

A PATTERN describes a rule which describes whichstrings are assigned to a token.

A LEXEME is the exact sequence of input charactersmatched by a PATTERN.

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Examples

lexeme pattern token

x * Id "x"

abc * Id "abc"

152 + Constant(152)

then then ThenKeyword

Many lexemes map to the same token. e.g. x andabc .

Note, some lexemes might match many patterns.e.g. "then" above. Need to resolve ambiguity.

Since tokens are terminals, they must be "produced"by the lexical phase with synthesized attributes inplace. (e.g. name of an identifier). e.g. id(x) andconstant(152)

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Syntax, Parse Trees & Grammars

Syntax (the physical layout of the program)

Grammars describe precisely the syntax of a language. Two kindsof grammars which compiler writers use a lot are: regular, andcontext free

Informal Definitions of:

Regular:

concatenation, union, star

Context Free:

only one symbol on the lhs of

a production

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Recursive Grammar Examples

Recursive Grammars describe infinite languages

list ::= [ num morenum ]

morenum ::= , num morenum

|

derives [ 2 ], [2,4], [2,4,6] ...

Exp ::= id

| Exp + Exp

| Exp * Exp

| ( Exp )

derives x, x+x, x+x+x, ...

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Parse Trees

Each nonterminal on the lhs of a production

"roots" a tree:

Each node in a tree with all its immediate children isderived from a single production of the grammar

We desire a program which constructs a parsetree from a string. Such programs are different forevery grammar, we some times use tools toconstruct such programs (yacc).

Exp

ExpExp +

Id Id

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Syntax Directed Translations

A syntax directed translation traverses a syntax tree

and builds a translation in the process.

Considerations

Tree Traversal orders Left to right?

right to left?

in-order, pre-order, or post-order

Where does the information about what to do in thetraversal come from? Attribute grammars

Inherited attributes

Synthesized attributes

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Example Translation Process

Translation as an abstract syntax to abstract syntax

transformerWe represent this as a grammar with actions { ... }. The

action is performed when that production is reduced.

Exp ::= Term termsterms ::= + Term { print "+" } term

|

Term ::= Factor factors

factors ::= * Factor { print "*" } factors

|

Factor ::= id { print id.name }

| ( Exp )

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Semantics

How do we know what to translate the syntax tree

into? How do we know if it is correct?

Semantics denotational semantics

operational semantics interpreters

Very useful in writing compilers since they give areference when trying to decide what the compiler

should do in particular cases.

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Over view

Compilation is a large process

It is often broken into stages

The theories of computer science guide us in writingprograms at each stage.

We must understand what a program means if we

are to translate it correctly. Many phases of the compiler try and optimize by

translating one form into a better (more efficient?)form.

Most of compiling is about pattern matchinglanguages and tools that support pattern matchingare very useful.

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Documents