Function Procedures

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Function Procedures
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Function Procedures

• Visual Basic includes built-in functions, like
  Sqr, Cos or Len, Left, Mid, Right.
• In addition, you can use the Function statement
  to write your own Function procedures.
• The syntax for a Function procedure is

PrivatePublic Function procedurename
(arguments) As typestatements End Function
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Function Procedures

• Like a Sub procedure, a Function procedure is a
  separate procedure that can take arguments,
  perform a series of statements, and change the
  value of its arguments.
• Unlike a Sub procedure, a Function procedure can
  return a value (other than through its
  arguments) to the calling procedure.

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Three Differences Between Sub and Function
Procedures

• Generally, you call a function by including the
  function procedure name and arguments on the
  right side of a larger statement or expression
  (returnvalue function( )).
• Function procedures have data types, just as
  variables do. This determines the type of the
  return value. (In the absence of an As clause,
  the type is the default Variant type.)
• You return a value by assigning it to the
  function name.

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The function in this example calculates the third
side, or hypotenuse, of a right triangle, given
the values for the other two sides
Function Hypotenuse (A As Single, B As Single) As
Single Hypotenuse Sqr(A 2 B 2) End
Function
You call a Function procedure the same way you
call any of the built-in functions in Visual
Basic
Width Val(Text1.Text) Height Val(Text2.Text)
Label1.Caption Hypotenuse(Width, Height)
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Private Sub cmdConvert_Click() picTempC.Cls
picTempC.Print FtoC(Val(txtTempF.Text)) End
Sub Private Function FtoC(t As Single) As
Single 'Convert Fahrenheit temperature to
Celsius FtoC (5 / 9) (t - 32) End Function
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Private Sub cmdCompute_Click() Dim radius As
Single, height As Single picOutput.Cls Call
InputDims(radius, height) Call
ShowAmount(radius, height) End Sub Private
Function CanArea(radius As Single, height As
Single) As Single 'Calculate surface area of a
cylindrical can CanArea 6.28 (radius
radius radius height) End Function Private
Sub InputDims(radius As Single, height As
Single) radius Val(InputBox("Enter radius of
can")) height Val(InputBox("Enter height of
can")) End Sub Private Sub ShowAmount(radius As
Single, height As Single) picOutput.Print "A
can of radius" radius "and height" height
picOutput.Print "requires" CanArea(radius,
height) "square units to make." End Sub