SIMSCRIPT II.5 Programming Language

Modelling Concepts
Experience has shown that some programmers prefer to write for each JOB, rather than for I
= 1 to N.JOB even if JOB has not been defined as a permanent entity. That is, they prefer not to
make up a local variable name (I in this instance) just to step through a sequence of values from 1
to N (N.JOB in this instance), but would rather use a name that is easy to remember and has some
meaning. To facilitate this, the phrase:
include entity name list
can be appended to a permanent entities statement, as in:
permanent entities include ADULT, COUNTRY and FISH
This phrase defines the listed names as permanent entities, without attributes, but with the associated
global variables entity and N.entity. The above statement defines the global variables
ADULT, N.ADULT, COUNTRY, N.COUNTRY, FISH, and N.FISH and permits such phrases as:
and
for every ADULT
for each COUNTRY
for all FISH
to be used. The following short example illustrates why this might be a useful shorthand.
Program preamble:
permanent entities include ELEMENT
Main program:
read N.ELEMENT
reserve LIST(*) as N.ELEMENT
for each ELEMENT, let LIST(ELEMENT) = 1
It should be clear that such a statement is impossible for temporary entities. Scattered throughout
memory, rather than stored sequentially, temporary entities cannot be indexed by ordinal numbers;
they can only be pointed to by set pointers. To process all the temporary entities of a given class,
the entities must be stored in a set as they are created, and must be processed by a statement that
deals with the set. This statement, which by its nature deals with both permanent and temporary
entities, has two basic forms:
1. for each variable of set
2a. for each variable from arithmetic expression of set
2b. for each variable after arithmetic expression of set
Form 1 selects entities that are members of an indicated set, in order of their ranking, assigning the
entity pointer values to the named variable. If the set is empty, all of the statements controlled by
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