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Control Structure

function functionName [parametersList] statementList end functionName

Platform Support
MacOS,Mac OS X,Windows,Linux
None required
Defines a custom function handler.

function myFunction

return "test"

end myFunction

Additional Comments
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Use the function control structure to implement a custom function.


The first line of a function handler consists of the word "function" followed by the function's name. If the function has any parameters, their names come after the function name, separated by commas.

The last line of a function handler consists of the word "end" followed by the function's name.


The functionName is a string up to 65,535 characters in length.

The parametersList consists of one or more parameter names, separated by commas.

The statementList consists of one or more Revolution statements.


The purpose of a function is to compute a value and return it to the handler that called the function. The function's value is returned by a return control structure within the function handler.

A function handler can contain any set of Revolution statements. Most functions contain a return statement, which returns the value to the calling handler. This example of a custom function uses two parameters and returns a string:

function reversedName firstName,lastName

-- firstName and lastName are parameters

put lastName,firstName into constructedName

return constructedName

end reversedName

You create a custom function by writing a function handler for it. When you use the function in a script, the function call is passed through the message path. When it reaches the object whose script contains the function handler, the statements in the handler are executed.

A custom function is called by name, just like a built-in function, as part of an expression. For example, this handler calls the custom function above:

on mouseUp

ask "What is your first name?"

put it into firstParam

ask "What is your last name?"

put it into secondParam

put reversedName(firstParam,secondParam) into field "Name"

end mouseUp

A function can call itself. The following example calls itself to compute the factorial of an integer:

function factorial theNumber

if theNumber <= 1 then return 1

else return theNumber * factorial(theNumber -1)

end factorial

Note: To declare a function that is local to the script it is contained in, prefix the declaration with private. For more information about this see the dictionary entry for the private keyword.

Changes to Revolution: The ability to declare private functions using the private keyword was added in Revolution 2.8.1

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