Basic Characteristics RAPID

Basic Characteristics RAPID Routines
3 Routines
3.1 Routine scope
There are three types of routines (subprograms): procedures, functions and traps.
- Procedures do not return a value and are used in the context of instructions.
- Functions return a value of a specific type and are used in the context of expressions.
- Trap routines provide a means of dealing with interrupts. A trap routine can be
associated with a specific interrupt and then, if that particular interrupt occurs
at a later stage, will automatically be executed. A trap routine can never be
explicitly called from the program.
The scope of a routine denotes the area in which the routine is visible. The optional
local directive of a routine declaration classifies a routine as local (within the module),
otherwise it is global.
Example: LOCAL PROC local_routine (...
PROC global_routine (...
The following scope rules apply to routines (see the example in Figure 2):
- The scope of a global routine may include any module.
- The scope of a local routine comprises the module in which it is contained.
- Within its scope, a local routine hides any global routine or data with the same
name.
- Within its scope, a routine hides instructions and predefined routines and data
with the same name.
Module1 Module2
Local Routine a
Local Routine b
Routine c
Routine d
Routine e
Local Routine a
Local Routine e
Routine f
Routine g
Routine h
Figure 2 Example: The following routines can be called from Routine h:
Module1 - Routine c, d.
Module2 - All routines.
A routine may not have the same name as another routine or data in the same module.
A global routine may not have the same name as a module or a global routine or global
data in another module.
RAPID Reference Manual 5-11