Basic Characteristics RAPID

Data Types Basic Characteristics RAPID
4 Data Types
There are two different kinds of data types:
4.1 Non-value data types
- An atomic type is atomic in the sense that it is not defined based on any other
type and cannot be divided into parts or components, e.g. num.
- A record data type is a composite type with named, ordered components, e.g.
pos. A component may be of an atomic or record type.
A record value can be expressed using an aggregate representation;
e.g. [ 300, 500, depth ] pos record aggregate value.
A specific component of a record data can be accessed by using the name of that
component;
e.g. pos1.x := 300; assignment of the x-component of pos1.
Each available data type is either a value data type or a non-value data type. Simply
speaking, a value data type represents some form of “value”. Non-value data cannot be
used in value-oriented operations:
- Initialisation
- Assignment (:=)
- Equal to (=) and not equal to () checks
- TEST instructions
- IN (access mode) parameters in routine calls
- Function (return) data types
The input data types (signalai, signaldi, signalgi) are of the data type semi value. These
data can be used in value-oriented operations, except initialisation and assignment.
In the description of a data type it is only specified when it is a semi value or a nonvalue
data type.
4.2 Equal (alias) data types
An alias data type is defined as being equal to another type. Data with the same data
types can be substituted for one another.
Example: VAR dionum high:=1;
VAR num level; This is OK since dionum is an alias
level:= high; data type for num
5-18 RAPID Reference Manual