[racket] About set-car! and set-cdr!

No, set! mutates variable bindings while set-car! mutates cons cells (the first slot of a data structure). 


On Mar 5, 2014, at 1:13 PM, Daniel Carrera wrote:

> Hello,
> 
> My understanding is that Racket intentionally does not provide set-car! and set-cdr! and that this is one of the ways in which Racket is not fully compatible with Scheme.
> 
> Am I right to think that it is trivially easy to add these features to Racket? Specifically, I'm thinking of:
> 
> 
> (define-syntax set-car!
>   (syntax-rules ()
>     ((_ l new_car) (set! l (cons new_car (cdr l))))))
> 
> (define-syntax set-cdr!
>   (syntax-rules ()
>     ((_ l new_cdr) (set! l (cons (car l) new_cdr)))))
> 
> 
> Or did I miss something?
> 
> Cheers,
> Daniel.
> -- 
> When an engineer says that something can't be done, it's a code phrase that means it's not fun to do.
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