1. Rational Expressions. relational operators. logical operators
Rational Expressions relational operators logical operators order of precedence

2. Expressions
any combination of variables, constants and functions that can be evaluated to yield a result
typically involve operators

3. Expressions 5 x
x + y
func(12.05, a, “Yvonne”)
cnt++
a = 3 + j

4. Relational Expressions
compare operands
used in decision making
evaluate to 1 (true) or 0 (false)

5. Relational Operators less than < greater than >
less than or equal to <=
greater than or equal to >=
a - b < 0 is equivalent to (a - b) < 0

6. Relational Expressions
Operand Relational Operand operator
price <
expression
* * *

7. Relational Expressions
Operand Relational Operand operator...
‘Z’ < ‘K’
expression

8. Values of Relational Expressions

9. Evaluating Expressions
int i = 1, j = 2, k = 3; i < j - k b i
* *

10. Evaluating Expressions
int i = 1, j = 2, k = 3; -i + 5 * j >= k + 1 i i i i b
* * *
* *

11. Evaluating Expressions
int i = 1, j = 2, k = 3; double x = 5.5, y = 7.7
x - y <= j - k + 1 (x - y) <= ((j - k) + 1) i r i b
* * *

12. Relational Operators Examples
Valid a < a > b -1.1 >= (2.2 * x + 3.3) a < b < c // syntactically correct but confusing
Not Valid a =< b // out of order a < = b // space not allowed a >> b // shift expression
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13. Equality Operators
Equal to = =
Not Equal to !=
Note this!
* * *

14. Values of Equality Expressions

15. Equality Operators Examples
Valid c == 'A' k != -2 y == 2 * z - 5
Not Valid a = b // assignment statement a = = b - 1 // space not allowed y =! z // this is equivalent to y = (!z)
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16. Numerical Accuracy
Many decimal numbers cannot be exactly represented in binary by a finite number of bits. Thus testing for exact equality can fail. Use the technique: |operand1 - operand2| < epsilon
Ex. x/y == 17 abs(x/y - 17) < *

17. Logical Operators
Negation (unary) !
Logical and &&
Logical or || *

18. Logical Operators: Examples
Valid a && b a || b && c !(a < b) && c 3 && (-2 * a + 7)
Not Valid a && // one operand missing a | | b // extra space not allowed a & b // this is a bitwise operation &b // the address of b
* *

19. Logical Operators: Examples
int a = 0, b = 3, c = 1, d =4;
a && !c || d b F b F b T
* * *

20. Logical Operators: Examples
int a = 0, b = 3, c = 1, d =4;
a && b || !c || d b F b F b T b F
* * * *

21. Logical Operators Expression Expression Equivalent !(a == b)
!(a == b || a == c)
!(a == b && c > d)
a != b
a != b && a != c
a != b || c <= d
* * *

22. Logical Expressions: Boolean
This is for version 4 only.
typedef int boolean;
const boolean TRUE = 1;
const boolean FALSE = 0;
ver. 5 & 6: bool is a data type

23. Truth Table for &&, ||, !

24. Operator Precedence and Associativity!
not
arithmetic
relational
logical

25. Logical Expressions b i r b b b b
char cv; double dv = 6.5; int iv = 4; ! (cv == ‘z’) && (abs(dv) || iv) || pow(3,2) b F b T i b T r b T b T
* * * * * * *

26. The Empty Statement
The empty statement is written as a semicolon. Example: ; // an empty statement
Other statements: a = b; // an assignment statement a + b + c; // legal, no useful work done cout << a() << "\n"; // a function call

27. Common Errors! = = means equality = used for assignment FALSE is zero
TRUE is nonzero
Boolean operators give a Boolean result
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28. Success comes before work only in the dictionary.
End Note:
Success comes before work only in the dictionary.
Success comes before work only in the dictionary.
Success comes before work only in the dictionary.