case using other equality-testing predicates

[David A. Moon <Moon@SCRC-STONY-BROOK.ARPA>]

    Date: Tue, 20 May 1986  23:45 EDT
    From: "Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>


	I'm sure some people will jump all over me for suggesting this,
	but it might be better to allow CASE to accept a :TEST keyword.  Which
	of these three syntaxes do you-all prefer?

	  (selector item equalp ("foo" ...) ...)

	  (case item :test #'equalp ("foo" ...) ...)

	  (cond ((equalp item "foo") ...) ...)

    I think that mixing keywords into a construct like Case that already has
    a complex syntax is likely to cause confusion.  

I agree.  But the other alternatives cause confusion, too.

						    I would prefer adding a
    new construct CASE-TEST that would look like

    (case-test #'equalp item ("foo" ...) ...)

    This is similar to your Selector, but without the odd treatment of the
    test function, and the name emphasizes the close parallel to Case.  I
    think it is best to put the test function before the item -- other
    things in the language put the testing function first.

So where would additional options, such as :KEY and an option that
controls whether or not the keys at the heads of the clauses are
evaluated, go in your syntax?

I guess it's obvious why Common Lisp doesn't currently have a way to do this
-- no one has thought of a syntax for it that anyone else likes.