READING
Chapter 5
Section 2

- boolean expressions
  - arithmetic operators
  - relational operators
  - conditional operators
  - boolean operators
    - takes boolean values as its operands and returns a boolean value
    - examples
      - AND 
        - syntax: &&
        - true if both operands are true
      - OR
        - syntzx: ||
        - true if at least one operand is true
      - NOT 
        - syntax: !
        - true if the operand is false
- reversing a relational operator means negating the boolean expression
- DeMorgan's Law
  - !(P && Q) <==> !P || !Q
  - !(P || Q) <==> !P && !Q
- arithmetic exception
- divide-by-zero error
- short-circuit evaluation
  - for the || operator, if the left operand is true, the right operand is not evaluated
  - for the && operator, if the left operand is false, the right operand is not evaluated
- operator precedence rules required for evaluating boolean expression
  - ! is considered a unary operator
  - relational operators come after additive operators
  - equality operators come after relational operators
  - && and || come after equality operators
  - operators with the same precedence are evaluated left-to-right
- | and & operations
  - same thing as || and &&, but doesn't short circuit
  - always use || and && in this course
- cannot do: 80 <= x < 90
  - type mismatch
- two values of data type boolean
  - true
  - false
  - boolean expression evaluates to one of these
- boolean flag tracks program settings or user preferences as a boolean
- don't need to directly compare a boolean to true or false, since already evaluates to one or the other
- choose identifiers that make it clear what the true and false values mean

Quick Check
1. a. true
   b. true && (false || false) <==> true && false <==> false
   c. ? && !(false) || ? <==> ? && true || ? <==> true || ? <==> true
   d. x < y || false <==> x < y
2. a. This actually assigns the value of y to both x and done.  What it probably means to do is assign whether x and y are equal to done; this would look like:
      done = x == y;
   b. According to precedence rules, first evaluate the parentheses (3 < 5) <==> true:
      2 < & && true + 1 == 3
      Next, evaulate the arithmetic operation true + 1... this is a type mismatch error: what does it mean to add a boolean and an integer?
   c. The third line is not a valid statement; here the equality operator is probably being confused with the assignment operator.  It should look like:
      quit = ( 34 == 20 ) && quit; // quit = true