User Defined Functions - Crestron SIMPL+ Programming Manual

Crestron SIMPL+

User Defined Functions

Programming Guide – DOC. 5789A
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programming task that has been predefined and given a name. Many of the examples
in previous sections of this document have used special types of functions called
system functions (or built-in functions). To employ system functions, use the
following format.
returnValue = FunctionName(Parameter1, Parameter2,...);
The above syntax is called a function call, because it tells the function (calls it) to
cause / perform an action. Notice that there are three elements to a function call.
First, it is identified by FunctionName, which must be unique for every system
function. The function name itself is followed by a comma-separated parameter list
enclosed in parentheses. Each function may have a fixed number of parameters, a
variable number of parameters, or no parameters at all. These parameters provide the
means to supply information to a function. For example, the itoa function converts
an integer value into its ASCII equivalent, which is very useful for creating strings to
control switchers. The single parameter to this function would be the integer value
that needs to be converted. Parameters can be any valid SIMPL+ expression.
Consider the statements:
returnValue = itoa(154);
returnValue = itoa(input_num);
returnValue = itoa(x*5-4);
All are valid function calls.
The variable to the left of the equal sign in the above function calls is used to hold
the return value of the function. This value can be either an integer or a string,
depending on the nature of the function. Clearly, if a given function returns an
integer value, an integer variable must be used to accept this value and a string
variable for those functions that return strings. In the itoa examples shown above, the
return value is the ASCII string which represents the number being converted. Thus,
returnValue in this case must be a string variable.
Some functions do not return any values at all. Thus it makes no sense to assign a
variable to a function as shown above. In addition, when using functions that do
return values, sometimes the return value may not be needed. In both cases, use the
Call keyword:
Call FunctionName(Parameter1, Parameter2, ...);
In this case, if the function being called does return a value, it is ignored.
Be aware as well that some functions may need to return more than one value. Since
functions can only have at most a single return value, there are some functions that
modify the values of the parameters that are passed to it.
SIMPL+ provides a large number of system functions, which are listed under a
number of categories in the latest revision of the SIMPL+ Language Reference
Guide (Doc. 5797). Many of these system functions are used as examples throughout
this manual.
The previous section details how to use system functions in SIMPL+. When
programming, there may be a need to create functions of your own to simplify your
programs. These functions are called user-defined functions. User-defined functions
Software
// constant param
// variable param
// general expression param
SIMPL+
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