Defining a Function

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Functions					Subroutines		Classes
Defining a Function	Predefined Functions	Tag Functions	Mathematical Functions	String Functions	Defining a Subroutine	Trigger Subroutines	Defining a Class

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Introduction

A function is a set of common tasks that can be defined once and called multiple times from within a PGM.

• A function is very similar to a subroutine. In many instances, either could be used.
• A subroutine can be used instead of a function if a value does not need to be returned.
• If a value does need to be returned then a function will need to be used.

Syntax

Function functName(argument list)
   ...statements...
   Return value
EndFunct

StrFunction functName(argument list)
  ...statements...
  Return string value
EndFunct

functName : unique name of the function, used to refer to the function.
argument list : optional list of parameters in the following format : (datatype parameterName, datatype parameterName, etc.)

• The function declaration must begin with the Function or StrFunction keyword and end with the EndFunct keyword.
• Use StrFunction if the function is going to return a string and Function if the function is going to return a numerical value.
• The parameter list cannot include instance of classes or variables passed by reference.
• Empty parentheses must be inserted, if no parameters are required by the function.
• A function may call itself (i.e. recursive functions are allowed). However, a true stack of the function variables is not used.
• Every possible execution path must use Return to ensure that the function is exited correctly.
• Local variables can be declared within the function, and their scope is limited to the function. However when a function calls itself recursively a local stack is not used.
• Any Const variable declared in a function is added to the global scope and is accessible outside of the function. A constant is not limited to the scope of the function.
• Function definitions cannot be nested (i.e. functions cannot be defined within functions).

Examples and Use

Function Examples

Number	Defining the Function	Calling the Function
Example 1	Function HoursToMinutes(Real timeInHours) Return timeInHours*60 EndFunct	Real TimeInMinute@ TimeInMinute = HoursToMinutes(3)
Example 2	Array c5 ;this function initialises the array function SetupArray() if (c5.Load("array.csv")) ;attempt to load the array from a file LogNote("loaded array") c5.SetLen(Max(c5.GetLen(),3)) ;ensure the array has at least three elements return 0 ;exit function endif c5.SetLen(6) ;set the length of the array c5.SetAll(1) ;set all the elements of the array to 1 return 0 endfunct	Sub InitialiseSolution() SetupArray() ;array gets setup when run is pressed or PGM is reloaded EndSub
Example 3	;this function places a random number in each element of the array function RndLoop(byte Cnt) while (Cnt>0) Cnt = Cnt - 1 c5.SetAt(Cnt, random(10) - 5) ;set the specified element in the array endwhile return 0 endfunct	if (Random(100)<10) RndLoop(c5.GetLen()) ;a ten percent chance that the function will be called else c5.SetAt(0, c5.GetAt(1) * c5.GetAt(2)) ;set c5[0] = c5[1]*c5[2] endif
Example 4	StrFunction MakeTag(Str Prefix, long No) return Concatenate(Prefix, "_", IntStr(No, 0)) endfunct	Str s1* s1 = MakeTag("P", 3)

Examples: Mathematical Function Examples, String Function Examples, Example PGM Files