Re: [Scheme-reports] [r6rs-discuss] redefining eqv?

[John Cowan <cowan@x>]

Peter Kourzanov scripsit:

> BTW...Can someone with enough grey hairs remember why we have the horde
> of predicates like =, eq?, equal? and eqv? What I understood is that
> eqv? is sort-of one-size-fits-all idea gone astray

EQV? is object equality, the identity of indiscernibles.  EQ? is an
variant of EQV? that can answer #f on on characters and numbers in exchange
for (hopefully) better performance.

= is type-specific equality on numbers, and corresponds to things like
CHAR=? and STRING=?.

EQUAL? was originally structural equality, but the exact way it works
is historical: it descends into pairs, vectors, and strings, but works
like EQV? on all other types.  Programmers are encouraged to substitute
a different structural-equality predicate if EQUAL? doesn't suit their
needs: it is not primitive.

The proposed EQUAL=? will be like EQUAL, but will employ = rather than
EQV? to compare numbers.

-- 
Híggledy-pìggledy / XML programmers            John Cowan
Try to escape those / I-eighteen-N woes;        http://www.ccil.org/~cowan
Incontrovertibly / What we need more of is      cowan@x
Unicode weenies and / François Yergeaus.

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