Eiffel Programming Language

1
Eiffel Programming Language

• By
• David Riley and Jason Thorpe
• December 3, 2002

2
Eiffel Overview

• Object-oriented
• Motivation designed to avoid some of the
  pitfalls of older OOP languages
• Introduced in 1985
• Created by Bertrand Meyer
• Developed by his company Interactive Software
  Engineering
• Named after Gustav Eiffel (designer of Eiffel
  Tower)
• The Eiffel Tower was completed on time and
  within budget, which should happen if you use
  Eiffel for your software projects
  http//www.engin.umd.umich.edu/CIS/course.des
  /cis400/eiffel/eiffel.htmlhistory

3
Eiffel Milestones

• 1985 Bertrand Meyer and Jean Marc Nerson begin
  development of Eiffel
• 1986 1st Eiffel compiler presented (April), 1st
  Customer Deliveries (December)
• 1987 Eiffel achieves commercial success
• 1991 Non-profit International Consortium for
  Eiffel (NICE) is founded NICE controls the
  standardization of the Eiffel language
• 1991 Publication of "Eiffel the language" by
  Bertrand Meyer (Prentice Hall)
• 1995 NICE presents Eiffel Library Kernel
  Standard (ELKS), which sets standards for basic
  Eiffel classes.
• 1997 NICE and the Eiffel Consortium organize
  Eiffel Struggle 97. Prizes awarded for Eiffel
  applications and Eiffel libraries.
• http//www.halstenbach.de/eiffel/eiffel8.htm

4
Supporting Platforms

• Eiffel Software's EiffelStudio environment is
  available for the major industry platforms
  Windows, Linux, Unix, and VMS.
• These implementations are all source-code
  compatible.

5
Eiffel Compilers

• ISE Eiffel v5.2
• free time-limited evaluation version Windows and
  Unix
• www.eiffel.com
• SmartEiffel the GNU Eiffel compiler
• Free All ANSI C machines
• http//smarteiffel.loria.fr/
• Iss-base
• Commercial free 90-day trial version Windows
  and Unix
• NonCommercial free Windows and Linux
• http//www.halstenbach.com/
• Visual Eiffel
• Commercial free evaluation (limited features)
  Windows and Linux
• http//www.object-tools.com/

6
Distinctive Features

• Portable runs on many platforms
• Open System has a C/C interface for code
  reusability
• Melting Ice Technology combines compilation
  with byte code interpretation for faster
  turnaround times after a change has occurred.
• Design by Contract enforced with assertions
  through invariance, preconditions and
  postconditions.
• Automatic Documentation documentation produced
  quickly by single click.

7
Distinctive Features (cont.)

• Multiple Inheritance - a class can inherit from
  multiple parents
• Repeated Inheritance - a class inherits from
  another through two or more parents
• Statically Typed catch errors at compile time
  not run time
• Dynamically Bound guarantee of right operation
  being applied depending on target object

8
Areas of Application

• Eiffel is not intended for any specific area but
  is used in
• Teaching
• not stuck within the confines of a single
  environment
• Eiffel allows students to focus on the concepts,
  not notational details
• Educators have remarked that it is easier to
  teach C, Smalltalk, or Java once Eiffel
  techniques are mastered.
• Rapid Prototyping
• covers analysis, design, and implementation in a
  single framework
• Financial Applications

9
I/O in Eiffel

• Attributes (Data)
• last_characterCHARACTER
• last_integerINTEGER
• last_realREAL
• last_stringSTRING
• last_boolean BOOLEAN
• Output routines
• put_character(cCHARACTER)
• put_integer(iINTEGER)
• put_real(rREAL)
• put_string(sSTRING)
• put_boolean(bBOOLEAN)
• put_new_line

• Input routines
• read_character
• read_integer
• read_real read_line -- result stored in
  last_string
• read_word -- result stored in
  last_string
• read_boolean

10
Basics in Eiffel

• I/O example
• io.put_string(Enter an Integer )
• io.read_integer
• int1 io.last_integer
• Basic Data Types
• INTEGER, CHARACTER, REAL, STRING, BOOLEAN
• Comments (--)

11
Control Structures

• Looping
• from--initialization
• until done -- BOOLEAN condition
• loop-- executable statements
• end

• Example
• from i 1
• until i 10
• loop
• io.put_int (i) io.new_line i i 1
• end

12
Control Structures

• Conditional
• ...
• if x gt 10 then ... statements ...
• elseif x gt 5 then ... elseif statements ...
• elseif x gt 0 then ... more elseif statements ...
  
• else ... else statements ...
• end

• Example
• ..
• if x gt 0 thenio.put_string(x is positive)
• elseif x lt 0 thenio.put_string(x is negative)
• elseio.put_string(x is 0)
• end

13
Control Structures

• Multi-Branch
• inspect input_character
• when 'y' then ... statements
• when 'n' then ... statements
• else ... if no match is found
• end

• Example
• ...
• State INTEGER
• State_1, State_2, State_3 INTEGER is unique
• ...
• inspect State
• when State_1 then some_action
• when State_2 then some_other_action
• when State_3 then another_action
• else no_action
• end

14
Arrays in Eiffel

• Declaration
• scores ARRAYINTEGER
• Creation
• !!scores.make(1,100)
• Functions
• count, lower, upper.
• Insertion
• scores.put(ltvaluegt, ltindexgt)
• Access
• scores.item(ltindexgt)

15
Design by Contract

• class COUNTER
• feature
• count INTEGER
• increment_by (inc INTEGER) is
• require
• inc gt 0
• do
• -- Implementation goes here
• ensure
• count old count inc
• end
• end

16
Hello World

• class HELLO_WORLD creation make feature
  make is do print("Hello World!!!! N")
  end --make end -- class HELLO_WORLD

17
Hello World (cont.)

• Class name - end (required)
• Creation Clause specifies the routines that may
  be called.
• Feature Clauses describes class features.

18
Type System

• Strongly typed
• Two categories reference type, expanded type
• Five basic types (expanded) INTEGER, REAL,
  DOUBLE, CHARACTER and BOOLEAN

19
Sorting Example

• class ARRAY_EXAMPLEcreation startfeature store
  ARRAYINTEGER
• -- function fill_array fills array with
  integers entered from keyboard fill_array is
  local indexINTEGER do from index
  store.lower -1 until index store.upper
  loop index index 1
  io.readint store.put(io.lastint,index
  ) end -- loop end -- fill_array

20
Sorting Example (cont.)

• -- function print array will print contents of
  array print_array is local indexINTEGER
  do from index store.lower-1 until
  index store.upper loop index
  index 1 io.putint(store.item(index))
  end -- loop end -- print_array

21
Sorting Example (cont.)

• -- function sort array will sort the elements
  of the array sort_array is local sortedBOO
  LEAN temp_item INTEGER index, last
  INTEGER do from last store.upper
  sorted false until sorted or else last
  store.lower loop from sorted true
  index store.lower -1 last last-1
  until index last

22
Sorting Example (cont.)

• loop index index 1
• if store.item(index) gt store.item(index1)
  then -- swap element with successor
  element temp_item store.item(index1)
  store.put(store.item(index),index1)
  store.put(temp_item,index) sorted
  false end -- if end loop end --
  loop end -- sort_array

23
Sorting Example (cont.)

• start is
• do
• !!store.make(1,7)
• fill_array
• sort_array
• print_array
• end -- start
• end -- ARRAY-EXAMPLE

24
References

• http//www.engin.umd.umich.edu/CIS/course.des/cis4
  00/eiffel/eiffel.htmlhistory
• http//www.halstenbach.de/eiffel/eiffel8.htm
• http//www.faqs.org/faqs/eiffel-faq/
• http//www.pi.informatik.tu-darmstadt.de/inf1/eiff
  -ref/