Any of the following .NET-provided types may be used for state variables and
action parameters: bool, byte, char, double, float, int, long, short, string as well
as any enum type defined by the model program.
In addition to these built-in types, you may also use the structured types and
collection types described in the rest of this chapter and the object types that we will
introduce later in Chapter 15.2
10.3 Compound values
Extending our model program with strings and integers doesn??™t change the way we
do state comparison. Just as in the previous chapters, two states are equal if their
variables contain the same values. The string data type is compatible with this kind
of equality: two strings are equal if they contain the same characters. Whether the
two strings share the same location in memory doesn??™t matter when asking if they
are equal. This kind of equality is called structural equality. It is the kind of equality
that matters for state comparison.
1 For the purposes of this chapter we use the term model program to mean a model program
written in C# source, compiled into a .NET assembly and loaded as a LibraryModelProgram
data type. The NModel package allows extenders to implement other kinds of model programs
that need not rely on .NET types for internal state.
2 The modeling framework provides an interface called IAbstractValue for extending the range
of types permitted in model programs.
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