CS 403: Programming Languages Lecture 16 Fall 2003 Department of Computer Science University of Alabama Joel Jones.

CS 403: Programming Languages

Lecture 16

Fall 2003

Department of Computer Science

University of Alabama

Joel Jones

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Overview

Announcements

M4 Macro Processor

Geoffrey Haynes

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m4 is a general purpose macro processor that can be used to preprocess C and assembly language programs, among other things. Besides the straightforward replacement of one

string of text by another, m4 lets you perform integer arithmetic file inclusion conditional macro expansion string and substring manipulation

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You can use built-in macros to perform these tasks or define your own macros. Built-in and user-defined macros work exactly the same way except that some of the built-in macros have side effects on the state of the process.

The basic operation of m4 is to read every legal token (string of ASCII letters and digits and possibly supplementary characters) and determine if the token is the name of a macro. The name of the macro is replaced by its defining text, and the resulting string is pushed back onto the input to be rescanned. Macros may be called with arguments. The arguments are collected and substituted into the right places in the defining text before the defining text is rescanned.

A small review of PythonJesse Booth

Named after Monty Python

Released to public in 1991

Syntax: cross between C and the Modula family

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Why Use Python?

Simple Syntax Easy to learn and quick to code

Portable between Unixes and even other operating systems

Large Standard Library Used for large complex projects with

many different developers

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Why is Python different?

Choice of Object-oriented programming Block structure is controlled by actual

indentation not brackets Easy to combine with C for performance-

critical applications Substantial speed gains

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PythonBin QiaoPython is a scripting language designed for close integration with C. Its syntax is rather like a cross between that of C and the Modula family.

It has a type system comparable in expressive power to Perl’s.

Python is generally thought to be the least efficient and slowest of the major scripting languages.

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Considerations of Using PythonProgrammability. Python is well suited to functioning as a glue language which is commonly used to implement the lower level operations.

Prototyping. Python provides a good environment for quickly developing an initial prototype.

Simplicity and ease of understanding. Python is powerful but very simple, which lets you learn the language more quickly, and then rapidly write code.

Java integration. Jython is a re-implementation of Python in Java that complies Python codes into Java bytecodes. The resulting environment has very tight, almost seamless, integration with Java.

RubyRobert Bradford

What is Ruby?

Ruby is a new object oriented programming language.

Though rarely used in the United States, it has become very popular in other areas of the world.

What are the advantages to using Ruby as a language?

Features similar to Perlo Process text files o Perform system management tasks

Few lines of code, but not cryptic

Syntax and semantics are simple

Ruby is open source

Platform independent… can be used on Windows, Unix or Linux

created by: created by: Yukihiro MatsumotoYukihiro Matsumoto

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Features Simple syntax Error handling Blocks in syntax

o Surrounded by either { } or do … endo Can be passed to methods

Integers can be used without counting internal representation No variable declarations, naming conventions denote scope

o 'var' = local variableo '@var' = instance variableo '$var' = global variable

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Code Analysis First… a definition of Fibonacci

o The basic Fibonacci series is a sequence of integers, starting with two 1's, in which each subsequent term is the sum of the two preceding terms. The series is sometimes used in sorting algorithms and in analyzing natural phenomena.

Demonstrated by this example:o Parallel assignmento Local variable creationo Looping structureo Function definitiono Output

Tool Command Language(Tcl)

By: Steven Kemp

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What is Tcl?

Tcl is a small language interpreter that can be linked with compiled C libraries.

It can also be used for embedded scripts, which are scripts that are called from C programs.

It was first released publicly in 1990.

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Advantages of Tcl It is extremely flexible and radically

simple. It has a totally consistent syntax. The interpreter itself can be

redefined from within Tcl. It’s compact design makes it more

efficient for smaller projects

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Minor Disadvantages of Tcl

The only data structure is association lists

Not good for use on large programs

Syntax is slightly odd, even though it is consistant

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JavaEric Jackson Developed by Sun Microsystems Created to be “write once, run anywhere” Automatically handles memory management. Can inherit from just about anything. Easy to learn. Style very similar to C and C++ MySet.java code to implement Set ADT

Brad Hutchinson

PHP Open source, server-side, HTML embedded scripting language used to create dynamic web pages.

Created in 1994, but during mid 1997 the development changed hands and the parser was rewritten from scratch to create PHP version 3.

Syntax is similar to that of Perl or C++.

The script is enclosed within special PHP tags, and because PHP is embedded within tags it is possible to jump between HTML and PHP.

This prevents having to actually write large amounts of HTML code using PHP.

Since it is executed on the server, the script cannot be viewed by someone accessing the web page.

Can perform any task that any CGI program can do, but its strength lies in its compatibility with many types of databases.

Can talk across networks using IMAP, SNMP, NNTP, POP3, or HTTP.

Little Ruby? Big Ruby?

What is Ruby?

Ruby is the interpreted scripting language for quick and easy object-oriented programming. It has many features to process text files and to do system management tasks (as in Perl). It is simple, straight-forward, extensible, and portable.

The Creator of RubyYukihiro Matsumoto, a.k.a Matz [email protected]

R. Allen Sanford

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Features of Ruby

Ruby has simple syntax, partially inspired by Eiffel and Ada. Ruby has exception handling features, like Java or Python, to make it easy to handle errors. Ruby's operators are syntax sugar for the methods. You can redefine them easily. Ruby is a complete, full, pure object oriented language: OOL. This means all data in Ruby is an object. Ruby's OO is carefully designed to be both complete and open for improvements. Ruby features single inheritance only, *on purpose*. Ruby features blocks in its syntax (code surrounded by '{' ... '}' or 'do' ... 'end'). These blocks can be passed to methods, or

converted into closures. Ruby features a true mark-and-sweep garbage collector. It works with all Ruby objects. You don't have to care about

maintaining reference counts in extension libraries. This is better for your health. ;-) Writing C extensions in Ruby is easier than in Perl or Python, due partly to the garbage collector, and partly to the fine

extension API. SWIG interface is also available. Integers in Ruby can (and should) be used without counting their internal representation. Ruby needs no variable declarations. It uses simple naming conventions to denote the scope of variables. Examples: simple

'var' = local variable, '@var' = instance variable, '$var' = global variable. So it is also not necessary to use a tiresome 'self.' prepended to every instance member.

Ruby can load extension libraries dynamically if an OS allows. Ruby features OS independent threading. Thus, for all platforms on which Ruby runs, you also have multithreading,

regardless of if the OS supports it or not, even on MS-DOS! ;-) Ruby is highly portable: it is developed mostly on Linux, but works on many types of UNIX, DOS, Windows 95/98/NT, Mac,

BeOS, OS/2, etc.

R. Allen Sanford

Information obtain from http://www.ruby-lang.org/en/

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DocumentationAll of the Previous information and more can be found at:

http://www.ruby-lang.org/en/

Other useful links are:

Great intro to ruby!

http://www.math.umd.edu/~dcarrera/ruby/0.3/

Ruby, Gui’s, and Tk toolkit.

http://httpd.chello.nl/k.vangelger/ruby/learntk/

Demonstration on generating html templates using ruby.

http://www.hillmanimages.com/912/tutor01.html

R. Allen Sanford

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RubyCharles B. Ward Ruby is an interpreted language, similar in a number of

ways to perl, php, and python. Ruby is an purely object oriented programming

language, like Smalltalk. Everything is an object, including numbers.

Ruby is *not* strongly typed. Ruby features only single-inheritance, instead allowing

classes to import modules of methods. Ruby has automatic memory management (garbage

collector).

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More Ruby Ruby naming conventions to denote the scope

of variables. 'var' = local variable '@var' = instance variable '$var' = global variable.

Ruby supports internal threading. (programs can be multithreaded independently of the operating system)

Ruby is compatible with LINUX, UNIX, DOS, Windows 95/98/NT, Mac, BeOS, OS/2, etc.

TCL (Tool Command Language)

Charles Lemont Howard

developed mainly by John Ousterhout

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Pros and Cons of TCL

PROS It is a high-level scripting language

~ lot less code to write to get job done

It runs on many platforms It is interpreted ~ execute code

without compiling and linking It is extensible It is embeddable in your

applications ~ meaning you can use TCL as an application language

terrific language for database applications

Tcl is free

CONS

TCL is interpreted ~ programs written in TCL are slow because TCL only deals with strings

Syntax checking only at runtime

Fundamental aspects of the Ruby programming language

Kunal Vyas

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About Ruby Yukihiro Matsumoto (Matz), a professional programmer working for and

open source company in Japan (netlab.co.ip) invented the Ruby programming language. 

Ruby is a "pure Object Oriented Language". Everything in Ruby is an object

Ruby is a "pure Object Oriented Language". Everything in Ruby is an object

Ruby uses pass-by-reference. Ruby also supports default formal argument assignment

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Ruby's features are as follows: Interpretive Variables have no type (dynamic typing) No declaration needed Simple syntax No user-level memory management Everything is object Class, inheritance, methods Singleton methods Mix-in by modules Iterators Closures Text processing and regular expression Bignums Dynamic loading Exception handling

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What made ruby different from other Programming Languages

Language: Ruby Added: Ruby Took Away:

C *Operatoroverloading

Object Orientation In light of the fact that C is the defining language for Ruby and Ruby is extendable using C, all the functionality of C is supported.

Smalltalk *Object Orientation*Everythingis an object!

1.Multiple Inheritance.

2. Ruby isn't as strict as Smalltalk with regard to object, inheritanceand class hierarchy

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Continue

Language: Ruby Added: Ruby Took Away: Perl *ScriptingPower

1. Clean Object Orientation - Ruby was initially designed with OO in mind, whereas Perl was extended to

support objects.

1.Scope rules in Ruby (default: local) eliminate the need for any 'my'

declarations. 2. Ruby eliminates a lot of Perl's syntax sugar without losingfunctionality making

Ruby less cryptic.

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Continue

Language: Ruby Added: Ruby Took Away:

Python *ExceptionHandling

1. Exception handling 2. Type coercion between small and long integers3. Mark and sweep garbage collection instead of aRef-counter garbage collection.

4. Inheritance / subclassing

1. Ruby's instance variables are prefixed by a at eliminating the need for 'self' declarations.

2. Python treats types and classes differently, Ruby treats them the same.

3. Tuples

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Continue

Language: Ruby Added: Ruby Took Away: Eiffel *Objectorientation and

simple syntax

Ruby is interpreted Compilation is not Required for Ruby.

Lisp *Lambda expressions

Object Orientation All those Parentheses

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For what applications would this language be suitable?

Text processing  CGI programming Network programming  XML programming GUI applications AI and Exploratory Mathematics General programming  Prototyping Programming education eXtreme programming 

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For what would it not be suitable? High traffic web applications 

Operating systems implementation

Compiler implementation

RubyAndré Taylor

“The object oriented scripting language”

André Taylor

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Introduction Ruby is the interpreted scripting language for quick

and easy object-oriented programming. It has many features to process text files and to do system management tasks (as in Perl). It is simple, straight-forward, extensible, and portable.

Ruby is highly portable: it is developed mostly on Linux, but works on many types of UNIX, DOS, Windows 95/98/NT, Mac, BeOS, OS/2, etc.

André Taylor

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Important features Ruby has simple syntax, partially inspired by Eiffel

and Ada. Ruby has exception handling features, like Java or

Python, to make it easy to handle errors. Ruby features a true mark-and-sweep garbage

collector. It works with all Ruby objects. You don't have to care about maintaining reference counts in extension libraries. This is better for your health. ;-)

André Taylor

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Important features cont. Ruby needs no variable declarations. Examples:

'var' = local variable '@var' = instance variable '$var' = global variable.

Ruby features blocks in its syntax (code surrounded by '{' ... '}' or 'do' ... 'end'). These blocks can be passed to methods, or converted into closures.

André Taylor

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Tcl/TkDavid Marshall

• Tcl (Tool Command Language) Created in 1989 by John Ousterhout An interpreted language with the main

purpose of integrating or tying together other applications

Tk An extension of Tcl created for component-

based GUI design

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Features of Tcl/Tk Extensible – Easy to add your own features

Designed so that added features feel as natural as the basic features of the language

Embeddable – Interpreter exists as C Library GUI building with Tk toolkit

Extremely fast to design and implement a GUI out of components provided by Tk

Cross Platform Runs on Windows, Mac, and Unix platforms

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Tcl Compared Often compared to Perl

Syntax is much simpler than Perl and has less of a learning curve

Easier to maintain – Perl syntax is much more complex, so reading and maintaining Tcl code is an easier task

Tk is available for Perl, but is less intuitive and clumsier because it was designed for Tcl

More information available at http://www.tcl.tk

Bash, XSLT, Dot, and CNathan Wiegand

What to do with

all those tools?

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Bash

The Bourne Again SHell - Created by Ritchie and Thompson from the Bourne Shell(sh).

Designed in order for people to better communicate with the system they were developing at AT&T

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XSLT

eXtensible Stylesheet Language Transform

Used to translate XML (eXtensible Markup Language) into another format (e.g. HTML, Word File, Dot)

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Dot

Open graph drawing software developed at AT&T

Used to present datastructures and other things which can be represented as graphs (i.e. file trees)

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File Tree Viewer

Start with a Bash script which walks your file tree and creates and XML file from the files it observes.

Next, use an XSL Transform to convert that XML document into a Dot Script.

Use Dot to convert this script into a nice Gif image for viewing.

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The Bash Script#!/bin/bash

dir=$(pwd) function dirExp {

echo "<node s=\"box\" c=\"red\" value=\"$2\">"cd "$1/$2"for i in $(ls -l -1 | grep ^- | gawk '{print $9}')do

VAL=$($dir/conv $(ls -l -1 $i | gawk '{print $1}'))if [ $(($VAL/100)) = 7 ]; then

color="green"else

color="white"fiecho "<node s=\"ellipse\" c=\"$color\" value=\"$i\"/>"

done

for i in $(ls -l -1 | grep ^d | gawk '{print $9}')do

dirExp "$1/$2" $i doneecho "</node>"

}dirExp $dir . > "$dir/dir.xml"cd $dirxsltproc -o structure.dot graph.xsl dir.xmldot -Tgif -o structure.gif structure.dotmv structure.gif ~/public_html

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The C file#include <stdio.h>

intmain

(int argc, char *argv[])

{int perm[3],

i;

if(argc!=2)fprintf(stderr,"Error\n");

for(i=1,perm[0]=perm[1]=perm[2]=0;i<strlen(argv[1]);i++) {perm[(i-1)/3]*=2;if(argv[1][i]!='-')

perm[(i-1)/3]++;}

fprintf(stdout,"%d%d%d\n",perm[0],perm[1],perm[2]);

return 0;}

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The Produced XML<node s="box" c="red" value="."><node s="ellipse" c="green" value="conv"/><node s="ellipse" c="white" value="conv.c"/><node s="ellipse" c="white" value="dir.xml"/><node s="ellipse" c="white" value="graph.xsl"/><node s="ellipse" c="white" value="Makefile"/><node s="ellipse" c="green" value="new.sh"/><node s="ellipse" c="white" value="structure.dot"/><node s="box" c="red" value="Project1"><node s="ellipse" c="green" value="a.out"/><node s="ellipse" c="green" value="conv"/><node s="ellipse" c="white" value="dir.tree"/><node s="ellipse" c="white" value="dir.xml"/><node s="ellipse" c="white" value="graph.xsl"/><node s="ellipse" c="green" value="NathanWiegand"/><node s="ellipse" c="white" value="NathanWiegand.cpp"/><node s="ellipse" c="green" value="NathanWiegand.gdb"/><node s="ellipse" c="green" value="output.txt"/><node s="ellipse" c="green" value="runme.sh"/><node s="ellipse" c="white" value="structure.dot"/><node s="ellipse" c="white" value="t"/></node><node s="box" c="red" value="Project2"><node s="ellipse" c="white" value="dir.tree"/><node s="ellipse" c="white" value="dir.xml"/><node s="ellipse" c="green" value="example.sh"/><node s="ellipse" c="white" value="file.dot"/><node s="ellipse" c="white" value="Makefile"/><node s="ellipse" c="white" value="structure.gif"/><node s="ellipse" c="white" value="t"/></node></node>

XSLT<?xml version = "1.0"?><xsl:stylesheet version='1.0'

xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>

<xsl:output method="text" omit-xml-declaration="yes"/>

<xsl:template match="/" xml:space="preserve">digraph treestruct {

<xsl:for-each select="//node"><xsl:call-template name="print-node"/></xsl:for-each>

}</xsl:template>

<xsl:template name="print-node"><xsl:variable name="this">

<xsl:value-of select="generate-id()"/></xsl:variable>

<xsl:variable name="label" xml:space="default"><xsl:text disable-output-escaping="yes">"</xsl:text><xsl:value-of select="@value"/><xsl:text disable-output-escaping="yes">"</xsl:text>,shape=<xsl:value-of

select="@s"/>,style=filled,fillcolor=<xsl:value-of select="@c"/></xsl:variable>

<xsl:value-of select="$this"/> [label=<xsl:value-of select="$label"/>];

<xsl:for-each select="node" xml:space="default"><xsl:value-of select="$this"/><xsl:text disable-output-escaping="yes"> -&gt; </xsl:text><xsl:value-of select="generate-id()"/>;

</xsl:for-each>

</xsl:template>

</xsl:stylesheet>

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Excerpt of the Dot filedigraph treestruct {

id2588904 [label=".",shape=box,style=filled,fillcolor=red];id2588904 -> id2588686;id2588904 -> id2587734;id2588904 -> id2587745;id2588904 -> id2587755;id2588904 -> id2588236;id2588904 -> id2588246;id2588904 -> id2588257;id2588904 -> id2588267;id2588904 -> id2588406;id2588686 [label="conv",shape=ellipse,style=filled,fillcolor=green];id2587734 [label="conv.c",shape=ellipse,style=filled,fillcolor=white];id2587745 [label="dir.xml",shape=ellipse,style=filled,fillcolor=white];

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The Product