Procedural Programming

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Analytica User GuideProcedural Programming

Analytica is mostly a 'declarative or non-procedural language. You create a model by defining variables, each with a definition expressing how to calculate it from other variables (or just a number or distribution). Because it has no (global) assignments, you can understand each definition (or formula) without worrying about the sequence of execution. There is no required sequence to write or read the sequence of variables. Analytica figures out what sequence to evaluate them at runtime without you having to tell it. This frees you, as a model builder or reader of someone else's model, from having to worry about how to control the evaluation sequence. That gives Analytica a huge advantage in clarity and reliability over most conventional computer languages that are procedural, like in Fortran, Visual Basic, C++, Javascript, and so on. Programming in such languages means spending a lot of effort designing (and then debugging) the flow of control using assignments, conditionals, and loops. That's why we say Analytica enables you to be a modeler without being a programmer.

However there are occasional situations where it's more convenient to express an algorithm in procedural form. For this reason, Analytica offers a set of programming constructs, described in this chapter, providing a general procedural programming language for those who want or need it. But most modelers can blissfully just ignore it!

Analytica lets you use these constructs to control the flow of evaluation only within the definition of a variable or function. Evaluating one variable or function cannot (usually) change the value of another global variables or functions. In this way, these procedural constructs do not affect the simple declarative relationships among variables and functions. (There are a few exceptions, like assignments in the OnChange of a user input or OnClick attribute of a Button, and the ComputedBy function, but even these are carefully designed to maintain the simple declarative structure.)

Sections

See Also


User-defined Functions and LibrariesProcedural ProgrammingReference sections
Comments


Lchrisman

29 months ago
Score 0
It says you can use these only within the definition of a variable or function, but in fact you can use procedural code in the OnClick of a button, which is a place where procedural style is often most likely to be useful.
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