The @PROD function is used to find the product of an expression across members of a set.  As an example, consider the model:

MODEL:

SETS:

 COMPONENTS: P;

ENDSETS

DATA:

 P = .95 .99 .98;

ENDDATA

 P_FAIL = 1 - @PROD( COMPONENTS( I): P( I));

END

Here we have a system of three components arranged in a series.  The probability that each component functions successfully (.95, .99, and .98) is loaded into attribute P in the model’s data section.  We then compute the probability that the entire system will fail, P_FAIL, by taking the product of the component probabilities and subtracting it from 1:

P_FAIL = 1 - @PROD( COMPONENTS( I): P( I));

As an aside, an interesting feature to note about this model is that we never initialized the COMPONENTS set.  When LINGO sees that an attribute of an undefined primitive set being initialized to n values in a data section, it automatically initializes the parent primitive set to contain the members: 1, 2, …, n.  So, in this example, LINGO automatically assigned the member 1, 2 and 3 to the COMPONENTS set.