Procedures - Functions and Subroutines
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(Continued from previous part...)
Function Procedure Example
To help you understand the concept of function procedure, I wrote the following the example, function_f2c.html:
<html>
<body>
<!-- function_f2c.html
Copyright (c) 2006 by Dr. Herong Yang. http://www.herongyang.com/
-->
<pre>
<script language="vbscript">
d = F2C(70.0)
document.writeln("Received Celsius = " & d)
d = F2C(212.0)
document.writeln("Received Celsius = " & d)
Function F2C(dFahrenheit)
document.writeln("")
document.writeln("Converting Fahrenheit = " & dFahrenheit)
dCelsius = (dFahrenheit - 32.0 ) / 1.8
document.writeln("Returning Celsius = " & dCelsius)
F2C = dCelsius
End Function
</script>
</pre>
</body>
</html>
Here is the output:
Converting Fahrenheit = 70
Returning Celsius = 21.1111111111111
Received Celsius = 21.1111111111111
Converting Fahrenheit = 212
Returning Celsius = 100
Received Celsius = 100
Easy to understand. Right?
Defining and Invoking Sub Procedures
A Sub Procedure is similar to a function procedure. It can be defined with the "Sub" statement:
Sub sub_name(argument_list)
statement_block
End Sub
where "sub_name" is the name of the sub procedure (subroutine),
and "argument_list" a list of variables used
to pass data into and/or out of the subroutine.
Of course, "argument_list" is optional.
Notice that subroutine does not return any values.
Invoking a subroutine is different than a function procedure. You can use one of the two syntaxes below:
1. Explicit call with "Call" statement:
Call sub_name(argument_list)
2. Explicit call with subroutine name:
sub_name argument_list
Both syntaxes will cause the system to:
- Stop execution in main code flow.
- Map data or variables based on the argument list.
- Execute the entire statement block defined inside the subroutine.
- Continue to execute main code flow.
If you want terminate a sub procedure early, you can use the "Exit" statement:
Exit Sub
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