This already happens for the local variables of a function, but it does not happen for global and static variables.

For the term "BDL" an object is a placeholder for one variable of a function.

In other words, the partial derivative takes the derivative of certain indicated variables of a function and doesn't differentiate the other variable(s).

In such situations, defunctionalization must be preceded by closure conversion (lambda lifting), so that any free variables of a function abstraction are passed as extra arguments to apply.

This assumption is necessary in BBO because species represent the independent variables of a function, and each island represents a candidate solution to a function optimization problem.

While discrete basis vectors are summed over a discrete index, continuous basis vectors are integrated over a continuous index (a variable of a function).