Built-in functions: in_progenitor function

in_progenitor function -- new in Simile v5.8

Usage: in_progenitor(expression of any type) returns that type

Definition: Used in a population submodel, returns the value of the argument expression  as it would be in the instance of that submodel containing the reproduction channel responsible for the instance being evaluated, or 0 or "false" in an instance that arrived via a channel other than reproduction. The argument can include the function prev(0) to refer to the value in the progenitor submodel instance of the component in whose equation the in_progenitor() function appears.

Note that a model that contains a circular set of influences can build and run properly if the input parameter associated with one of the influences is only used in the argument of an in_progenitor() function. This is because since the value of the argument is calculated for the progenitor instance and then used in the offspring instance, and the progenitor always comes before the offspring in evaluation order, there is no actual circular dependency.

Important: If the progenitor instance has been removed (see Extermination) then using this function will return meaningless values, and may cause model execution to be aborted due to memory access violations. To avoid this problem, make the in_progenitor function itself the argument of an at_init() function, e.g., at_init(in_progenitor(index(1))). If this is done, the inner argument will be evaluated for the progenitor instance when the offspring instance is created -- at which time the progenitor definitiely exists -- and then retained within the offspring instance's data structure. The only reason for not doing this would be if changes in the value in the progenitor continue to affect the offspring, and offspring never outlive their progenitors, e.g., in an L-systems model of tree branching.

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