function

Defines a custom function handler.

# Metadata

Platforms: desktop, server, mobile OS: mac, windows, linux, ios, android, web Introduced: 1.0 Security:

# Syntax

[private] function functionName [parametersList] statementList end functionName

# Params

- functionName : A string up to 65,535 characters in length. - parametersList : The parametersList consists of one or more parameter names, separated by commas. - statementList : The statementList consists of one or more LiveCode <statement|statements>. The final <statement> is typically a <return(control structure)> <statement>, which sends the value derived in the <function> <handler> back to the <statement> that <caller|calls> the function.

# Examples

function myFunction return "test" end myFunction

function cubeIt pNum return pNum * pNum * pNum end cubeIt

# Description

Use the function control structure to implement a custom function.

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

A function handler can contain any set of LiveCode statements. Most functions contain a return statement, which returns the value to the caller. 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 call the function in a handler, 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 execute.

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.

# Tags

# See

- **keyword:** [[$]], end, private, string - **function:** functionNames, param, paramCount, result - **glossary:** call, caller, control structure, execute, expression, handler, message path, parameter, return, statement - **control structure:** exit, return