ANSI Common Lisp  7 Objects 7.6 Generic Functions and Methods
7.6.6 Method Selection and Combination
When a generic function is called with particular arguments, it must
determine the code to execute. This code is called the
effective method for those arguments.
The effective method is a
combination of the applicable methods in the generic function
that calls some or all of the methods.
If a generic function is called and no methods are
applicable, the generic function no-applicable-method
is invoked, with the results from that call being used as the
results of the call to the original generic function. Calling
no-applicable-method takes precedence over checking for acceptable
keyword arguments; see Section 7.6.5 Keyword Arguments in Generic Functions and Methods.
When the effective method has been determined,
it is invoked with the same arguments as were passed to the generic function.
Whatever values it returns are returned as the values
of the generic function.
7.6.6.1 Determining the Effective Method
7.6.6.2 Standard Method Combination
7.6.6.3 Declarative Method Combination
7.6.6.4 Built-in Method Combination Types
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