Evaluation of functional maps in an expression

A single evaluation of a functional map requires one object for each input argument. The result of the evaluation is always one output object. As with functions and operators, when a functional map is used in an expression, evaluation sets for that expression might cause the functional map to be evaluated many times.

Consider the following expression:

MakeForm ( EntryForm:Input , GroupInfo:Input )

If there are two occurrences of GroupInfo and four occurrences of EntryForm, the map MakeForm will be evaluated once per combination of EntryForm and GroupInfo-a total of (2 x 4) = 8 times.

Consider another expression:

Fmap ( a:Input , b:Input , c:Input )

The objects a, b, and c have only Input in common. The expression that contains the Fmap reference will be evaluated once per combination of a, b, and c.

To illustrate how the functional map will be evaluated, use a very simple data file of a's, b's, and c's. Each time the map is evaluated, one a object, one b object, and one c object are selected. The first time the map is evaluated, the data objects are a1, b1, and c1. The next time it is evaluated, the data objects are a2, b1, and c1, and so on.

An important difference in how the Map Designer evaluates a functional map in an expression is when an input argument evaluates to none.

See When an Input Argument of a Function Evaluates to NONE.