get-fixed-index-assignments

Arguments: metaclass direct-supers class-name

This function is defined in patch pma025.001 (and perhaps later release numbers). That patch must be loaded for this function to work.

If one value is returned or if the second (map) value is nil, then the first slot will be assigned the first returned value, and subsequent slots will be assigned using a simple increment by 1 for each unassigned slot. Note that if a slot in the class being defined is given a fixed-index option, then no assignment is added to that slot, and the increment for the next slot will start from there. If a second value is returned, then it must be a vector of index assignments which will be used to assign fixed-index values to as yet unassigned slots, starting with the second unassigned slot (the first unassigned slot will be assigned based on the first value returned from this generic function). The index values in the map may be in any order - they need not be in ascending order - but they must not conflict with any other fixed-index assignments either in the class being defined or in the superclasses.

The default method

(method excl:get-fixed-index-assignments (fixed-index-class t t)

This method returns one value: the first index to use which is guaranteed not to conflict with any index values specified by either the class to be defined or any of its superclasses. This style of index assignment could be thought of as an append style; a method on a subclass of fixed-index-class could return a fill style or a hybrid style which could be implemented by returning a map of all of the currently used indexes in the class or its superclasses.

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This page is new in the 10.1 release.
Created 2019.8.20.