SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
value being stored. This alternative provides the convenience of tally and accumulate
specifications without wasting entity storage space by storing unnecessary information. Declare
OVERRUN as a dummy variable in the preamble declaration:
define OVERRUN as a dummy variable
This declaration saves one location in each JOB entity created. Such savings, resulting from dummy
specifications, can be significant in models requiring a large number of statistical computations on
many entities.
Any preamble-defined variables and attributes can be declared as dummy, but these should only be
used for tally or accumulate purposes.
5.6 Model Verification and Debugging
Even carefully prepared programs are rarely error-free. Errors in a program fall into two categories:
syntactic errors and logical errors. Errors in the syntax of SIMSCRIPT II.5 programs are detected
and reported by the language compiler. Error and warning messages are displayed, referring, where
appropriate, to the program statement line where the error was detected, and usually identifying the
incorrect word or symbol. Such errors may then be corrected and the program resubmitted for compilation.
A listing of the error messages produced by the compiler, together with an explanatory
message for each, is contained in each SIMSCRIPT II.5 user's manual. The compiler also produces
a numbered listing of the statements within each program section compiled, including the preamble
section. Following this listing of each section is a cross-reference listing that names each global
and local variable, entity type, and subprogram referenced, specifying for each its mode, dimensionality,
and the line numbers in which references appear. Variables used as implicit subscripts are
included in this cross-reference. Careful examination of the cross-reference can identify misspelled
variable names, which may otherwise by default be taken as declarations of new local variables,
references to undeclared functions, which may be taken as references to subscripted arrays, and other
typographical errors in program preparation.
If syntax errors are detected within subprograms (but not within the preamble section), it is only
necessary to recompile those incorrect routines, preceding them with a copy of the preamble statements
as input to the compiler. This feature of separate routine compilation facilitates the preparation
of large programs containing many routines.
Recall that some special routines may be generated by the compiler to perform such tasks as set
management, entity creation, and statistics gathering. If the preamble has not been altered, the redundant
regeneration of these routines may be suppressed by prefixing the word old to the preamble
definition. In addition, even the compiled listing of this preamble may be suppressed by titling
it very old preamble in the definition.
Alternatively, we should explain that certain statements and programming constructs in
SIMSCRIPT II.5 are implemented by generating a number of additional SIMSCRIPT II.5
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