[plt-scheme] equal? operator

Thanks!

Danny Yoo schreef:

>On Sun, 20 Nov 2005, Hans Oesterholt-Dijkema wrote:
>
>  
>
>>Is it possible to extend the equal? operator for new (structure) types
>>in mzscheme?
>>    
>>
>
>Hi Hans,
>
>
>According to:
>
>http://download.plt-scheme.org/doc/299.400/html/mzscheme/mzscheme-Z-H-4.html#node_idx_744
>
>doing equal? on structures should just work, as long as the structures are
>inspectable.  For example:
>
>;;;;;;
>  
>
>>(define-struct pair (x y))
>>(define p1 (make-pair 1 2))
>>(define p2 (make-pair 1 2))
>>(equal? p1 p2)
>>    
>>
>#f
>;;;;;;
>
>Here, because the structure isn't inspectable, equal? doesn't work.  But
>if we make an inspectable structure:
>
>;;;;;;
>  
>
>>(define-struct pair (x y) (make-inspector))
>>(define p1 (make-pair 1 2))
>>(define p2 (make-pair 1 2))
>>(equal? p1 p2)
>>    
>>
>#t
>;;;;;;
>
>equal? now is allowed to do the kind of equality testing we'd expect.
>
>  
>