CSC/ECE 517 Fall 2009/wiki3 20 i7

From Expertiza_Wiki
Revision as of 08:50, 18 November 2009 by Stphung (talk | contribs)
Jump to navigation Jump to search

Liskov substitution principle

The Principle

The Liskov substitution principle was introduced by Barbara Liskov in 1987 and is concerned with subtype contractual correctness. Based on a paper from 1994 the principle states, "Let q(x) be a property provable about objects x of type T. Then q(y) should be true for objects y of type S where S is a subtype of T.". This means that for every parent type T, subtype S should be able to be substituted in for it and the behavior of the program should remain exactly the same.

Preconditions

Preconditions cannot be strengthened. <Explain in english> <Example>

Postconditions

Postconditions cannot be weakened. <Explain in english>

Invariants

Invariants must be preserved. <Explain in english>

Retrieved from "https://wiki.expertiza.ncsu.edu/index.php?title=CSC/ECE_517_Fall_2009/wiki3_20_i7&oldid=28299"