How would I go abo开发者_如何学运维ut writing my own eqv? or equal? in scheme? Would I just do a cond and look for symbol?, number?, etc and return the appropriate #t or #f?
As per R5RS, the minimum specifications for an implementation of eqv?
(when passed two arguments obj1
and obj2
) to evaluate to #t
are:
obj1
andobj2
are both#t
or both#f
. (how two boolean literals evaluate to the same value is implementation dependent).obj1
andobj2
are both symbols and
(string=?
(symbol->string obj1)
(symbol->string obj2)) =)
=> #t
obj1
andobj2
are both numbers, are numerically equal (=
), and are either both exact or both inexact.obj1
andobj2
are both characters and are the same character according to thechar=?
procedure.- both
obj1
andobj2
are the empty list. obj1
andobj2
are pairs, vectors, or strings that denote the same locations in the store (See section 3.4 of R5RS).obj1
andobj2
are procedures whose location tags are equal (Alambda
expression is conceptually tagged with a storage location. What that means varies between Scheme implementations. Also see section 4.1.4 of R5RS).
equal?
could be implemented in terms of eqv?
as it recursively compares the contents of pairs, vectors, and strings, applying eqv?
on other objects such as numbers and symbols.
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