Visual Basic Programming II Lecture 6

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Visual Basic Programming IILecture 6

• MIS233
• Instructor Larry Langellier

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This Week Numeric Functions

• How functions work
• Writing your own functions
• Using Built-in functions
• Numeric conversion
• Mathematical
• Random Number generation
• Financial

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Numeric Functions

• A Function is like a Procedure except it returns
  a value
• Basic Syntax
• PublicPrivate Function name (arg-list) As
  type
• function statements
• End Function
• Example
• Public Function Volume(Length, Width, _
• Height) As Double
• Volume Length Width Height
• End Function
• Assign a value () to the function name to return
  the value

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Calling the Function

• Calling a Function is similar to calling a
  Procedure, except since the function returns a
  value you must store the return value in a
  variable
• Examples
• Dim dblBoxVolume As Double
• dblBoxVolume Volume (4, 5, 6)
• lblVolume.Caption Volume (2, 4, 6)

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Common Mistakes

• Not assigning a return value inside the function
• Not storing the return value to a variable when
  you call the function
• Not separating argument values with commas
• lblVolume.Caption Volume (3 5 7)
• Defining the function with the keyword Sub

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Writing Numeric Function Procedures

• Visual Basic contains a number of built-in
  numeric functions which well see in a little
  bit
• You will also want to write your own numeric
  functions on numerous occasions
• Examples
• 16.1 Convert Race Results
• 16.2 Returning the Highest/Lowest Values

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Built-In NumericConversion Functions

• Int(number)
• removes the fractional part of number, returns
  the next lower number for negatives
• Fix(number)
• removes the fractional part of number
• Round(expression , numdecs )
• rounds the expression to the specified number of
  decimals (0 is the default)
• CInt(expression), CLng(expression),
  CSng(expression), CDbl(expression),
  CCur(expression), CStr(expression),
  CVar(expression)
• Converts expression to the specified data type

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Built-In Mathematical Functions

• Exp(number) Atn(angle)
• raises e to a power - arctangent of an
  angle
• Log(number) Sin(angle)
• computes the natural log - sine of an angle
• Sqr(number) Cos(angle)
• the square root - cosine of an angle
• Abs(number) Tan(angle)
• the absolute value - tangent of an angle
• Sgn(number)
• the sign of number
• Example 16.3

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Generating Random Numbers

• Randomize( )
• Seeds the random number generator
• Rnd (number)
• lt 0, The same value every time
• gt 0, The next random number value (the default)
• 0, The value most recently generated
• Returns a value between 0 and 0.999999
• Example
• an integer between 1 and 6
• Int((Rnd 6) 1)
• Examples 16.4 and 16.5

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Financial Functions - Annuities

• Used when working with Interest and its effect
  on the value of money lets look these up in
  the Help System
• FV(rate, nper, pmt, pv)
• What will the future value be?
• IPmt(rate, per, nper, pv)
• How much interest is paid/received for a specific
  period?
• NPer(rate, pmt, pv, fv)
• How many payment periods will be required?
• Pmt(rate, nper, pv, fv)
• How much should the payment be per period?
• PPmt(rate, per, nper, pv, fv)
• How much principle is paid for a specific period?
• Rate(nper, pmt, pv, fv)
• What interest rate will yield the desired results?

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Financial Functions Cash Flow

• Computations related to cash flow a series of
  payments and receipts
• NPV(rate, values())
• Net Present Value
• PV(rate, nper, pmt, fv)
• Present Value
• IRR(values())
• Internal Rate of Return
• MIRR(values(), finance_rate, reinvest_rate)
• Modified Rate of Return
• Example 16.6

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Details

• Next Class
• Read Chapter 17 String Functions
• Homework 7 is due prior to the start of class
• Following Class
• The Midterm Project will be due at the beginning
  of class