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[racket] FOR loop

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Mon May 5 08:33:33 EDT 2014		 
Why don't you use the one that's available in Racket? 


On May 4, 2014, at 11:09 PM, Zee Ken wrote:

> Hi. I am trying to implement the for loop.
> 
> My for loop structure:
> 
> (for     <variable>     <initial>     <limit>     <increment>     <body>)
> 
> 
> (define (fvar exp) (cadr exp))
> (define (fstart exp) (car (cddr exp)))
> (define (flimit exp) (car (cdddr exp)))
> (define (fincr exp) (cadr (cdddr exp)))
> (define (fbody exp) (caddr (cdddr exp)))
> 
> (define (for exp)
>   (begin
>     (define (iter current limit step)
>           (if (< current limit)
>                 (begin
>                       (eval (fbody exp))
>                       (iter (+ current step) limit step))
>                 (display "\n")))
>     (iter (fstart exp) (flimit exp) (fincr exp))))
> 
> I tried executing (for '(i 1 10 4 (display 2))) and it showed:
> 
> 222
> 
> in the REPL.
> 
> It is working well when constants are involved. How can I incorporate the variable binding?
> 
> I tried extracting the variable, that is, (fvar exp), it returns 'i=(quote i). How can I define i to be the initial value?
> 
> 
> -- 
> Thanking You,
> Zee Ken
> ____________________
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>  http://lists.racket-lang.org/users

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