SIMSCRIPT II.5 Programming Language

Modelling Concepts
In general, all set owner and member attributes are treated as integer-valued and have names
formed by prefixing a letter and a period to the set name. The declarations:
permanent entities
every CITY owns a CLUB
temporary entities
every RESIDENT may belong to the CLUB
define three attributes for the owner entity of CLUB and three attributes for its member entities. Because
CITY is a permanent entity, its owner attributes are stored as three arrays, with base pointers
F.CLUB(*), L.CLUB(*), and N.CLUB(*). RESIDENT, being a temporary entity, has its member
attributes, P.CLUB, S.CLUB, and M.CLUB, stored in locations within each individual entity.
Every program commences execution with empty sets. As a program proceeds, statements are executed
that file entities in sets, examine sets, and remove entities from sets. Set memberships
change dynamically when file and remove statements alter set pointers, changing relationships
that affect set membership and set ranking. The file statement has two basic forms:
1a. file arithmetic expression first in set
1b. file arithmetic expression last in set
2a. file arithmetic expression
before arithmetic expression in set
2b. file arithmetic expression
after arithmetic expression in set
The words first or last are optional. When both are omitted, file last is implied; the statements:
and
file arithmetic expression last in set
file arithmetic expression in set
are equivalent.
In each of the forms, the words the or this are optional before the expression or the set name, as
in:
file the BIRD in the NEST
file this JOB first in this QUEUE
file MYDOG after YOURDOG in the KENNEL
Used in this context, each arithmetic expression must evaluate to an entity identifying value. It must
be either the pointer value addressing a temporary entity, obtained from a previous create statement,
or an integer number indexing one of the N.entity permanent entities of a specific type.
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