In a reader position, the content of an operand is only read, and not changed, when the statement is executed. Data objects can be specified as followed in reader positions:
- Specification of a literal.
- Specification of a data object visible at this point using a name
dobj, a field symbol
<fs>, or a data reference
dref->*dereferenced using the dereferencing operator
drefis specified in full). The names of data objects here include the specification of a text symbol using text-idf, where
idfis the three-character code of the text symbols, or concatenations of reference variables. If a field symbol is used, it must be assigned to a memory area and a data reference must point to a data object. Otherwise an unhandleable exception is raised.
As an alternative to specifying a text symbol using
text-idf, the three-character code of a text symbol can be appended to the text field literal in parentheses:
... '...'(idf) ...
If the text symbol exists in the currently loaded text pool, then the content of the text symbol is used instead of the text field literal, otherwise the literal is used.
- If the data object is an internal table, the expressions
dobj, <fs>, or
dref->*can also be used. An exception to this is when specifying the internal table of a table expression, where
cannot be appended to the name. For
dobj, this ensures that the table body is addressed and no header lines. If an internal table does not have a header line, its simple name
) is interpreted as the table body at all operand positions. However, if an internal table does have a header line, its simple name
) is interpreted as the header line and not the table body at almost all operand positions. The operand positions, used to interpret an internal table name with a header as the internal table, are listed under internal tables with headers.
- Specification of a subarea of a character-type or byte-type data object (or a character-type initial part of a structure) by specifying an offset/length.
- In some positions, number values must be specified directly as digits, although it is often not possible to specify a sign (which is not the case with numeric literals). Examples are numbers specified in declarative statements for the length of elementary data objects or for the initial memory requirements of internal tables.
- Text symbols cannot be listed in all reader positions. For example, they are not permitted for specifying the target of dynamic executions.
- A system field should only be specified as an operand in a reader position if its content is not set by the same statement, since otherwise undefined behavior may occur.
- The predicate expressions IS
IS BOUNDcan be used to check whether field symbols or data references.
- A data reference variable with a generic static type can only be deserialized using the statement
ASSIGN dref->* TO <fs>.
- In many reader positions, functions or expressions can be specified as well as data objects.