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5. Function

A function is a set of tasks that are performed by passing parameters to the function and returning a value.
A function is called into action by its identifying name. Here are SQeeLfs functions.
SQeeL Functions
System and User-Defined Functions
There are two types of functions in SQeeL program: System functions and User-defined functions.
System functions are intrinsic (build-in) functions that cannot be changed.
String, Date and Time, Database, and OS functions are available for use.
You can also write user-defined functions in SQeeL to provide functionality that is not available in system or build-in functions.
You can specify any name for user-defined functions that are called as needed.


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Calling Functions
Using a function is referred to as gcalling a functionh.
A calling function indicates that data is passed to the function to proceed and result is returned by the function.
System functions and user-defined functions are called as follows.

Function (Actual Argument [, Actual Argument 2, ..])

Example. Calling A Function
var1 = func1("abc", 101, a + b) A FUNC, a user-defined function, is called by passing a set of argument values of gabch, 101, and a+b to this function.

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Arguments
Arguments refer to the values passed to a function when calling the function.
An gactual argumenth is the value in a calling program passed to the function. A gdummy argumenth is the value assigned in a called program.

Actual Argument
    An gactual argumenth is the value in a calling program passed to the function. (Some functions do not require any arguments.)
    You can call other functions or perform arithmetical operations in an actual argument list because you can write an expression in the actual argument list.
    To specify multiple actual arguments, they need to be separated by a comma (,).

Dummy Arguments
    A gdummy argumenth is the value assigned in a called program.
    If you change any dummy arguments, the actual arguments with which these dummy arguments are associated are also changed.
    To specify multiple dummy arguments, they need to be separated by a comma (,).

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System Functions

Following functions are available as the system build-in functions in SQeeL program.

Date and Time Functions
    These functions allow you to get the current date and time. They format the date and time in different ways.
String Functions
    These functions manipulate strings such as replacing, searching, getting string length.
File Functions
    These functions manage file input/output.
OS Functions
    These functions allow you to execute operating system commands.
Database Functions
    These functions allow you to use Oracle database server effectively.
CGI Functions
    These functions are only available when running as CGI program.
For more information about calling functions and return values, see gSQeeL Function Referenceh.


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User-Defined Functions

You can create a user-defined function that has the form that starts with function statement and ends with endfunction statement. You can write any SQeeL codes in it.
Declaring User-Defined Functions
To declare a function, it must start with function statement and end with endfunction statement.
To specify multiple dummy arguments, they need to be separated by a comma (,).
You cannot declare other functions in a function definition.
The return statement must be used in the user-defined function to pass the result back to main program that calls the user-defined function.

function [function_name] ([dummy_argument1], [dummy_argument2], ..)
        Function process
endfunction


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Functions
Function name must follow the name rule below:
  • After the first character, use a letter, underscore
  • Name must start with a letter (either a letter or underscore (_))
  • You cannot use reserved words.
Dummy Arguments
A dummy argument is classified as a variable name in the function statement. A dummy argument is assigned to the value in the function to proceed. It is a symbolic name that is associated with an actual argument.
To specify multiple dummy arguments, they need to be separated by a comma (,).
  • Itfs not necessary to declare the variable name before using it
  • If you change dummy arguments, the actual arguments are also changed.
  • A dummy argument has the same scope as local variables
Processing Block ( SQeeL Block)
You can write any commands and statements in this block.
However, the use of the local variable in a function must follow the rules below.
  • A local variable is only available in the block which the variable is defined in.
  • This cannot be used from external program
  • You can specify the same name as far as if the variable is defined as a local one.
Return Value
The return statement must be used in the user-defined function to pass the result back to main program that calls the user-defined function.
  • The only one expression is specified as a return value
  • If a function that does not use the return statement completes, it returns 0.
  • If the type of a return value is an array, it automatically changes the type of variable that is assigned to, although the variable is declared as scalar.
Example: Creating a Function 
function plus(a, b)
	local ans
	ans = a + b
	return ans
endfunction
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