Basic Characteristics RAPID

Routines Basic Characteristics RAPID
3.2 Parameters
The parameter list of a routine declaration specifies the arguments (actual parameters)
that must/can be supplied when the routine is called.
There are four different types of parameters (in the access mode):
- Normally, a parameter is used only as an input and is treated as a routine variable.
Changing this variable will not change the corresponding argument.
- An INOUT parameter specifies that a corresponding argument must be a variable
(entire, element or component) or an entire persistent which can be
changed by the routine.
- A VAR parameter specifies that a corresponding argument must be a variable
(entire, element or component) which can be changed by the routine.
- A PERS parameter specifies that a corresponding argument must be an entire
persistent which can be changed by the routine.
If an INOUT, VAR or PERS parameter is updated, this means, in actual fact, that the argument
itself is updated, i.e. it makes it possible to use arguments to return values to the calling
routine.
Example: PROC routine1 (num in_par, INOUT num inout_par,
VAR num var_par, PERS num pers_par)
A parameter can be optional and may be omitted from the argument list of a routine
call. An optional parameter is denoted by a backslash “\” before the parameter.
Example: PROC routine2 (num required_par \num optional_par)
The value of an optional parameter that is omitted in a routine call may not be referenced.
This means that routine calls must be checked for optional parameters before an
optional parameter is used.
Two or more optional parameters may be mutually exclusive (i.e. declared to exclude
each other), which means that only one of them may be present in a routine call. This
is indicated by a stroke “|” between the parameters in question.
Example: PROC routine3 (\num exclude1 | num exclude2)
The special type, switch, may (only) be assigned to optional parameters and provides a
means to use switch arguments, i.e. arguments that are only specified by names (not
values). A value cannot be transferred to a switch parameter. The only way to use a
switch parameter is to check for its presence using the predefined function, Present.
Example: PROC routine4 (\switch on | switch off)
...
IF Present (off ) THEN
...
ENDPROC
Arrays may be passed as arguments. The degree of an array argument must comply
5-12 RAPID Reference Manual