CS 4448 - Spring 1998
Object-Oriented Programming and Design
Discussion 6.2.2
by
Phil Hugger

Summary of Eiffel Discussion

• Eiffel is a OO language, as well as a programming environment and an analysis tool.
• What are the goals of ISE Eiffel?
• Rapid prototyping - get your software out fast.
• Lower maintenance costs - write bug-free software the first time.
• Quick reaction to market demands - easily adaptable software.
• Preserve your investment - robust, reusable software.
• Eiffel is an open system, best used as a combination technology.
• Includes a sophisticated C and C++ interface which supports:
• Calling C functions from Eiffel
• Accessing C++ classes and components (functions or "methods," data members, constructors, destructors, etc.) from Eiffel.
• Accessing Eiffel mechanisms from C or C++ through Cecil library (C-Eiffel Call-In Library)
• Automatically producing a "wrapper" Eiffel class from a C++ class.
• Benchmarks show a speed similar to C and Fortran, and in some cases better.
• Uses a unique incremental compilation technology, called "melting ice technology."
• Combines traditional compilation (for fast, efficient code) with bytecode interpretation (allowing fast turnaround after changes) to use the advantagesof both methods.
• Final version of code is then translated from the optimized bytecode into C, in a process called "finalization".
• Eiffel written in itself.
• Provides a full set of platform-specific libraries which include:
• WEL (Windows Eiffel Library) for Windows 95/NT
• PEL (Presentation-manager Eiffel Library) for OS/2
• MEL (Motif Eiffel Library) for Unix
• Relational database interfaces:
• EiffelStore library with mappings available for ODBC (windows databases), Oracle, Sybase, and Ingres.
• Eiffel has a fully graphical environment.
• Analysis and design workbench
• Editor
• Browser/Debugger
• Documentation
• Design by contract - systematic engineering approach to building reliable software.
• Invariants
• All operations guaranteed to maintain this condition.
• Preconditions
• Must be true when method is called.
• Postconditions
• If precondition is true, postcondition is guaranteed.
• Build software together with the arguments that justify it's correctness.
• Can select which assertions are monitored at runtime - assertion levels
• no check
• preconditions only
• postconditions only
• "Short form" notation gives the users of a class a precise description of the interface and assertions without revealing the implementation.
• Supports inheritance and clean mulitple inheritance.
• Renaming mechanism eliminates name clashes, selection facility removes ambiguities resulting from multiple redelacrations.
• Statically typed
• Errors are caught at compile time, not run time.
• Dynamically bound
• Guarantees that the right version of an operation will always be applied depending on the target object.