Enumerations

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Related topics

• Model Code

Topic contents

• Introduction and outline
• Enumerations as dimensions
• Enumeration index validity

Introduction and outline

Content to follow.

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Enumerations as dimensions

Each dimension of a multi-dimensional parameter, derived table or entity array is declared using an enumeration. In RiskPaths, for example,

parameters
{
    //EN Age baseline for first pregnancy
    double  AgeBaselinePreg1[AGEINT_STATE];
...
};

declares the 1-dimensional array parameter AgeBaselinePreg1 using the enumeration AGEINT_STATE, which is a partition whose declaration is

partition AGEINT_STATE //EN 2.5 year age intervals
{
    15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40
};

In C++ model code, an element of an array can be referenced using an index. For example, in the following code fragment

TIME Person::timeFirstPregEvent()
{
...
    dHazard = AgeBaselinePreg1[age_status]
...

AgeBaselinePreg1 is indexed by the attribute age_status to obtain an age-specific hazard.

Enumeration index validity

Index errors are a common source of errors in C++ programs. Such errors are typically not detected by the C++ compiler and often manifest only indirectly when the program is executed. They can be hard to detect and resolve, because they manifest outside of a program's logic, by reading or modifying unrelated locations in memory.

In model code,
an index is invalid if it falls outside the lower and upper integer limits of an enumeration dimension. For example, the parameter ProbMort

parameters
{
...
    double ProbMort[LIFE]; //EN Death probabilities
};

is declared using the range LIFE:

range LIFE //EN Simulated age range
{
    0,100
};

The model code fragment

TIME Person::timeDeathEvent()
{
...
    if (ProbMort[integer_age] >= 1)
...
}

would be invalid if integer_age was less than 0 or greater than 100.

The option

options index_errors = on;

causes the OpenM++ compiler to generate code which verifies that all indices are valid during a model run.