SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
Because an entity identification can itself be an attribute, as in the case of a pointer, nested entity
references can be made, as in:
S.KENNEL(F.KENNEL(FARM))
which reads as "the successor of the first in KENNEL of FARM" and has the same value as
S.KENNEL(DOG) because F.KENNEL(FARM) = DOG. Any level of entity nesting is possible as
long as all nested expressions evaluate to entity identifiers.
When a third DOG is created and filed, the entity records are as shown in figure 4-16. Additional
creations and filings are analogous.
A file last statement has an effect similar to file first, but operates on the opposite end of
a set. If our example program segment were written with the statement file DOG last in
KENNEL(FARM), after executing three creates and files the entity records would appear as in figure
4-17.
The file before and file after statements are described with a different example. Assume
the entity record organization shown in figure 4-18 was created by the following program statements:
create a DOG called MYDOG
file MYDOG first in KENNEL(FARM)
create a DOG called YOURDOG
file YOURDOG first in KENNEL(FARM)
The statements:
create a DOG
file the DOG after YOURDOG in KENNEL(FARM)
insert the entity record for the newly created DOG after the entity record pointed to by the variable
FIDO. The resulting entity record organization is shown in figure 4-19.
156