SIMSCRIPT II.5 Programming Language

Advanced Topics
Program statements that employ optional attributes:
let WHICH = 1 ‘’INDICATING THE FIRST OPTIONAL ATTRIBUTE
let X = OPTIONAL(CITY)
If an entity CITY has an entity filed in its OPTIONS set with a CODE value of 1, X is set to the
VALUE of the entity. If an entity CITY has no such entity filed in OPTIONS, X is set to
DEFAULT(1).
The program can be made even more straightforward if functions are used to define the optional
attributes themselves. If RAPID.TRANSIT is an optional attribute of CITY, it can be defined and
used by the following statements:
define RAPID.TRANSIT as an integer function
routine RAPID.TRANSIT(CITY)
define CITY as an integer variable
let WHICH = 1
return with OPTIONAL(CITY)
end
The diagram in figure 6-13 shows the record structures for a temporary entity of the type CITY that
has several "normal attributes" and several "optional attributes."
CITY 67 000 000
F.OPTIONS 1 1 is the code for
RAPID.TRANSIT
L.OPTIONS
P.OPTIONS
N.OPTIONS
S.OPTIONS
NAME
POPULATION 3 500 000
STATE 4 4 is the code for
EDUCATION.EXPENSE
P.OPTIONS
S.OPTIONS
.
DEFAULT .
1 0 .
2 0 257 532 000
3 100 57 57 is the code for
MUNICPAL.DEBT
. . P.OPTIONS
. . S.OPTIONS
. .
97 200
98 10
99 4510
100 -1
Figure 6-13. Record Structure
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