Object-Oriented Programming Using C Third Edition

1
Object-Oriented Programming Using CThird
Edition

• Chapter 2
• Evaluating C Expressions

2
Objectives

• Use C binary arithmetic operators
• Learn about the precedence and associativity of
  arithmetic operations
• Examine shortcut arithmetic operators
• Use other unary operators
• Evaluate Boolean expressions
• Perform operations on struct fields

3
Using C Binary Arithmetic Operators

• Five simple arithmetic operators
• the addition operator ()
• the subtraction operator ()
• the multiplication operator ()
• the division operator (/)
• the modulus operator ()

Note that they are all binary operators
4
Using C Binary Arithmetic Operators (continued)
5
Using C Binary Arithmetic Operators (continued)

• Addition, subtraction, multiplication, division,
  or modulus of any two integers results in an
  integer
• For example, 7 / 3 evaluates to 3
• Mixed expression operands have different data
  types
• For example, 3.2 2
• Unifying type
• Data type of the value that occupies more memory
• All types in the expression are temporarily
  converted to a unifying type

6
Using C Binary Arithmetic Operators (continued)

• The order of precedence of unifying types from
  highest to lowest
• long double
• double
• float
• unsigned long
• long
• unsigned int
• int
• short
• char

7
Explicit cast
8
(No Transcript)
9
Using C Binary Arithmetic Operators (continued)

• Cast transform a value to another data type
• Implicit cast automatic cast, or transformation,
  that occurs when you assign a value of one type
  to a type with higher precedence
• int answer 2.0 7
• Explicit cast deliberate cast
• intResult static_castltintgt(doubleVariable)
• intResult (int)doubleVariable
• static_castltintgt('A') // is 65

Preferred method in C
10
Using Modulus

• Modulus () gives the remainder of integer
  division
• 7 3 results in 1
• -10 8 produces -2
• -10 -8 produces -2
• Can be used only with integers
• Can be used to extract digits from numbers
• 6,543 10 is 3
• 6,789 10 is 9

11
Using Modulus (continued)

• Check digit digit added to a number that
  validates the authenticity of the number
• A simple algorithm
• Assume an account number named acctNum is 123454
• Remove the last digit
• Perform modulus on the new number with an
  arbitrary value, say 7 (remainder shortAcctNum
  7)
• Compare the last digit of the original account
  number (lastDigit acctNum 10) with the
  remainder from the check digit calculation

12
Precedence and Associativity of Arithmetic
Operators

• Multiplication, division, and modulus are said to
  have higher arithmetic precedencethat is, they
  are performed first in an arithmetic statement
  with multiple operations
• Associativity rule that dictates the order in
  which an operator works with its operands
• In C, most operators have left-to-right
  associativity

13
Precedence and Associativity of Arithmetic
Operators (continued)

• When C evaluates a mixed arithmetic expression,
  the following steps occur
• The leftmost operation with the highest
  precedence is evaluated
• If operands are the same type, the result is the
  same data type
• If the operands are different types, C performs
  an implicit cast and the result is the same type
  as the one that occupies more memory
• Each subsequent , /, or operation is evaluated
  in the same manner from left to right

14
Precedence and Associativity of Arithmetic
Operators (continued)

• Steps (continued)
• The leftmost operation with the lower precedence
  ( and ) is evaluated
• If operands are the same type, the result is the
  same type
• If operands are different types, C performs an
  implicit cast and the result is the same type as
  the one that occupies more memory
• Each subsequent or operation is evaluated in
  the same manner from left to right
• Use parentheses to override precedence rules

15
Precedence and Associativity of Arithmetic
Operators (continued)
16
Shortcut Arithmetic Operators

• Two categories of shortcut arithmetic operators
  are
• Compound assignment operators
• Increment and decrement operators

17
Compound Assignment Operators

• Add and assign operator ()
• Subtract and assign operator ( )
• Multiply and assign operator ()
• Divide and assign operator (/)
• Modulus and assign operator ()

18
Increment and Decrement Operators

• Prefix increment operator
• count
• Postfix increment operator
• count
• Prefix decrement operator
• --count
• Postfix decrement operator
• count--

19
Using Shortcut Arithmetic Operators
20
Other Unary Operators

• Positive value operator
• 5
• Negative value operator
• -8
• Address operator ()
• x

21
Other Unary Operators
Hexadecimal number
22
Evaluating Boolean Expressions

• Relational operators evaluate the relationship
  between operands
• Used to evaluate Boolean expressions
• Boolean expression interpreted as true or false

23
Evaluating Boolean Expressions (continued)

• The unary operator ! is the not operator
  reverses the true/false value of an expression
• coutltlt(9gt2) displays a 1
• coutltlt!(9gt2) displays a 0
• !0 is 1
• !1 is 0
• !5 is 0
• !-5 is 0
• Dont confuse with

24
Performing Operations on struct Fields
25
Performing Operations on struct Fields (continued)
26
You Do It Using Arithmetic Operators

• int a,b,c
• double x,y,z
• a 13
• b 4
• x 3.3
• y 15.78
• c a b
• coutltlta b is ltltcltltendl
• z x y
• cout ltltx y is ltltzltltendl
• c a / b
• coutltlta / b is ltltcltltendl
• c a b
• coutltlta b is ltltcltltendl

27
You Do It Using Arithmetic Operators (continued)
28
Using Prefix and Postfix Increment and Decrement
Operators

• a 2
• c a
• coutltlta is ltltaltlt and c is ltltcltltendl
• a 2
• c a
• coutltlta is ltltaltlt and c is ltltcltltendl

29
Using Prefix and Postfix Increment and Decrement
Operators (continued)
30
Using Operators with struct Fields

• coutltltPlease enter a student's credit hours
• cingtgtoneSophomore.creditHours
• coutltltPlease enter the student's grade point
  average
• cingtgtoneSophomore.gradePointAverage
• coutltltThe number of credit hours is ltlt
• oneSophomore.creditHoursltltendl
• coutltltThe grade point average is ltlt
• oneSophomore.gradePointAverageltltendl
• hoursRemaining HOURS_REQUIRED_TO_GRADUATE
  oneSophomore.creditHours
• coutltltThis student needs ltlthoursRemainingltlt
• more credit hours to graduateltltendl

31
Using Operators with struct Fields (continued)
32
Summary

• There are five simple binary arithmetic
  operators addition (), subtraction (),
  multiplication (), division (/), and modulus ()
• When you mix data types in a binary arithmetic
  expression, the result is always the same type as
  the type that takes the most memory to store
• Several shortcut operators for arithmetic exist,
  such as , prefix , and postfix

33
Summary (continued)

• Boolean expression evaluates as true or false
• In C, the value 0 is always interpreted as
  false all other values are interpreted as true
• Fields contained within structures are used in
  arithmetic and Boolean expressions in the same
  manner as are primitive variables