Applications and Equivalences

 

https://slides.com/georgelee/ics141-applications-equivalences/live

What do we use the logics for?

Translating Into English

System Specifications

Sounds pretty boring

http://clientsfromhell.net/

Automated Testing

Where you write code twice

(once as a test case, once to get the test to pass)

Consistent Specifications

A system specification that does not contain any contradictions.

Boolean Searches

Boolean Searches

SQL Queries

SELECT * FROM users 
WHERE status = 1 
    AND (email = 'test@hawaii.edu' OR email = 'admin@hawaii.edu');

Logic Puzzles

Logic Circuits

Tautologies and Contradictions

Tautology

A compound proposition that is always true, no matter what the values of the propositional variables are.

 

i.e. p v ¬p

Contradiction

A compound proposition that is always false, no matter what the values of the propositional variables are.

 

i.e. p ^ ¬p

Contingency

A compound proposition that is neither a contradiction nor a tautology (pretty much anything else)

Logical Equivalences

Equivalent

Two expressions that have the same truth values in all cases are logically equivalent.

Or, let and q be two compound propositions, p and q are logically equivalent if pq is a tautology.

 

Sometimes denoted as  

List of Equivalences

There's Too Many!

Refer to Tables 6, 7, 8 on pages 27-28

DeMorgan's Laws

  • ¬(p ^ q) ≡ ¬p v ¬q
  • ¬(p v q) ≡ ¬p ^ ¬q

Applications and Equivalences

By George Lee

Applications and Equivalences

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