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Re: building other EQUIV?-like predicates

This page is part of the web mail archives of SRFI 85 from before July 7th, 2015. The new archives for SRFI 85 contain all messages, not just those from before July 7th, 2015.

On 3/10/06, Sebastian Egner <sebastian.egner@xxxxxxxxxxx> wrote:
> In many cases I need an application-specific
> equivalence which is not among the predefined
> ones.

This is true, the equivalence of leaf nodes does seem on
the ad-hoc side.  Although a SELECT-EQUIV? might make
sense for SRFI-67, I don't think it fits well into this SRFI.

A simpler extension is to provide an optional equivalence
predicate argument as in SRFI-1's MEMBER and ASSOC:

  (equiv? obj1 obj2 [eq-fn])

where EQ-FN defaults to something like

  (lambda (a b)
    (if (string? a) (and (string? b) (string=? a b)) (eqv? a b))