SmallTalk

1
SmallTalk

• Tessa Adderley
• SWE6743 OO Programming Language Presentation
• 09/17/07

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Inheritance Single Multiple or Otherwise?

• Inheritance is different in Smalltalk
• known as differential or inheritance programming
• Inheritance is restrictive
• Supports only single inheritance
• Others beg to differ
• Claims of multiple inheritance being used have
  been made

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Class or Component Reuse

• Within Smalltalk, certain provisions or
  facilities have been provided to aid in class or
  component reuse.
• class library
• Finding classes can prove problematic because
  of
• size of the library
• vocabulary differences between the user and the
  library
• inconsistency between libraries

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Class or Component Reuse (contd)

• SmallTalk also has a tool called System browser
• Helps find classes through categorizing
• Categories such as
• Classes and methods
• Used to help navigate class library
• Disadvantages
• Slow
• Time Consuming

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Class or Component Reuse

• To solve this problem ClassExpert came to the
  rescue!
• Research prototype tool
• For use with Visual Works/Smalltalk
• Helps in class retrieval by using functional
  specification provided by the user
• Fast
• Aids in finding the right class and appropriate
  superclass

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Information Hiding How is it utilized?

• utilized by using internal and external views of
  objects
• by partitioning the program into modules
• external view is the view of the object that the
  user sees
• internal view is the view seen by the objects
  implementors
• fundamental in Smalltalk programming

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Usability Then

• Jacob Nielsen and John T. Richards learnt
  Smalltalk for the very first time
• Found that it was hard for them despite their
  many years of programming experience
• Had trouble with
• The distributed code
• What the Smalltalk programs actually did
• Browsing classes
• System Assistance
• Felt that it would have been better to learn from
  someone already well versed with SmallTalk

8
Usability Now

• Dolphin and Squeak used by Daniel and I
  respectively
• Tutorials were very helpful
• If I had to learn by myself it MAY be a loss..
• IDE complicated if youve never seen anything
  like it.
• More setting up the background work than actual
  programming

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Reality How much is this thing gonna cost me?!?

• Trial or Evaluation versions are available for
  most commercial environments.
• Most commercial versions are inexpensive ranging
  from 149 - 475
• Exceptions
• VisualAge Smalltalk (6995) and SmallTalk MT
  (895)
• SmallTalk MT personal version (99)
• All other environments are either offered in
  free, full versions, or trial, evaluation
  versions.

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Sooooo.Why should I buy it?

• Selling points have varied
• Depends on what the user wants
• Examples
• Portability VisualWorks
• Database connectivity ObjectStudio
• Mission critical applications GemStone/S
• Marketing based on what the users goal is, not
  really on the technical stuff.

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Pros and Cons

• Pros
• Can be used in almost if not all applications
• Cost effective if not for commercial use
• Lots of tutorials, sites and references
• Many versions to choose from

• Cons
• A little hard for beginning programmers
• Information hiding makes it difficult to browse
  classes if you want to reuse