gf-discriminator-value

Arguments: generic-function

Returns the value (defined below) for the generic-function, if it exists and is unique. For discriminators which treat the generic-function as a slot accessor, the value is the slot's index into the slot vector (a fixnum). For the checking style discriminator, the value is the effective-method which has only ever been used in calls to this generic-function. Some discriminators do not have a single value stored, but instead the value calculated by the discrminator is either an index or an effective-method stored as part of the cache line held for the discriminator. In this case the value returned by gf-discriminator-value is nil.

See Appendix: Effective-method selection in Allegro CL CLOS and Associated Optimizations in implementation for more information on this function.

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Created 2019.8.20.