Review Question

1
Review Question

• What kind error is it when I try to multiply a
  number in a program by 1000 and store in a
  variable, but the variable is too small for the
  number to fit?
• Old Odometer problem.

2
Arithmetic Expressions

• 02/04/11

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Programs do Calculations

• Example in cs117/ch2/circle.cpp

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Arithmetic Operators

• Algebra
• , - unary
• x,
• , - binary
• xn

• C
• , - unary
• , /,
• , - binary
• no exponent

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Precedence

• 1. Parenthesis
• 2. Unary , -
• 3. , /,
• 4. Binary , -

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Values of the Following?

• 5020
• 20.0 6.0/2.0 3.0
• 20.0 6.0/(2.0 1.0)
• 5 -a 14 ? ,assume a -2

7
Associativity

• Left to right
• x y z
• Right to left
• --z
• x y 0

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No Implied Multiplication

• x 2(y z) //Error
• x 2(y z) //Ok

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Assignment Operator

• variable expression
• expression on right evaluated
• result stored in variable
• int x, y
• x 9(74)
• y x 20

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Example
11
int operations

• int i 5
• int j 3
• int k
• k i / j //Result of divide truncated
• k i j
• Result int when operands are int

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Careful with Integer Fractions
13
Fraction -- Whats Wrong?
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Implicit Type Conversion

• Assume variables
• int k 5, m 4, n
• double x 1.5, y 2.1, z
• Type automatically converted
• n x
• z m

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Implicit Type Conversion

• Assume variables
• int k 5, m 4, n
• double x 1.5, y 2.1, z
• z k /m //Result of op. Same as Operands
• y m 1.5 // mixed types

16
Explicit Type Conversion
17
Explicit Type Conversion
int kids, families double average kids
21 families 8 average (double)kids/families

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Next

• Additional Operations
• Functions
• Read Chapter 3 for Wednesday

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Exercises for Study

• p. 55, 1 ,3, 4