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- To: Common-Lisp-Object-System@SAIL.STANFORD.EDU
- Subject: lambda-list congruence
- From: David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>
- Date: Mon, 28 Sep 87 13:48 EDT
Here is the lambda-list congruence writeup, revised to use CLtL's terminology
for keyword arguments instead of introducing new terminology:
Changes to Lambda-list Congruence Rules (p.1-20): Rules 1, 2, and 6 remain the
same, except for wording problems, while rules 3-5 need to be replaced to
implement the new rules for &KEY and to fix the interaction among &KEY, &REST,
and &ALLOW-OTHER-KEYS. The new rules for congruence are the following:
These rules define the congruence of a set of lambda-lists, including the
lambda-list of each method for a given generic function and the lambda-list
specified with DEFGENERIC, if present. For (SETF generic) methods, these
rules apply to the effective lambda-list produced by combining the two
specified lambda-lists according to the rules on page nnn.
1. Each lambda-list must have the same number of required parameters.
2. Each lambda-list must have the same number of optional parameters.
Each method can supply a different default for an optional parameter.
3. If any lambda-list uses &REST or &KEY, each lambda-list must use one or
more of these.
4. If the DEFGENERIC uses &KEY, each method must accept all of the
keyword names mentioned after &KEY in DEFGENERIC, either by accepting
them explicitly, by specifying &ALLOW-OTHER-KEYS, or by specifying &REST
but not &KEY. Each method can accept additional keyword arguments of its
own. The checking of the validity of keyword names is not done in each
method; instead it is done in the generic function.
5. The use of &ALLOW-OTHER-KEYS need not be consistent across lambda-lists.
If &ALLOW-OTHER-KEYS is used in any lambda-list, then any keyword arguments
may be used in the call to the generic function.
6. The use of &AUX need not be consistent across methods.