SIMSCRIPT II.5 Programming Language

Discrete Simulation Concepts
If the random number drawn is 0.95, SAMPLE = 42.6
Random values defined as linear can only be real-valued. Interpolations are done in real
arithmetic, and the accuracy is determined by the machine representation. Rounding is done in the
above examples for illustration only.
If the mode of random variables does not agree with the background mode, the mode must be specified
in a define statement. This define statement may also be used to specify a random number
stream other than the default stream (number 1). On some implementations, this stream number
may be declared to be a variable, which must evaluate to the number of a valid stream, whenever
used.
Example:
Define SAMPLE as a random attribute of an entity JOB. The values of SAMPLE are real. Sampling
is done using linear interpolation and random stream 6.
every JOB has a SAMPLE random linear variable
define SAMPLE as a real, stream 6 variable
Sampling is always automatic. That is, a random variable behaves as a right-hand function. Whenever
a random variable appears, a routine that performs sampling is executed. SIMSCRIPT II.5
generates these routines using random number stream 1 unless otherwise specified.
5.4.3 Programmer-Defined Random Variables
If the you require a type of sampling other than step or linear, you must omit the words step or
linear from the definition of the random variables and provide your own sampling function.
Three system functions are provided for sampling (table 5-7). They correspond to the type of
lookup previously described.
Table 5-7. System Sampling Functions
Function Mode Arguments Description
istep.f integer v,e Returns a random sample from table v using stream
e.
lin.f real v,e Returns a random sample from table v using interpolation
and stream e.
rstep.f real v,e Returns a random sample from table v using stream
e.
Because of the special storage assigned to random variable sample values and probabilities, special
input treatment is necessary. When a variable defined as random appears in a free-form read statement,
the following occurs:
1. Pairs of free-form data values are read until a mark.v character appears.
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