[plt-scheme] Adding a list

From: Robby Findler (robby at cs.uchicago.edu)
Date: Sat Feb 17 15:49:20 EST 2007

Please consult your instructor, not us.

But you may wish to check your parenthesis too.


On 2/17/07, Teresa Stanton <tms43 at clearwire.net> wrote:
> I'm very new to Scheme and need some help.  I'm trying to write a function
> that accepts an accumulating function(summation, product) and a list of
> numbers and returns the accumulation of the operation on each element of the
> list.  So, if '(1 2 3 4) was supplied to the function and an operation 'sum'
> that adds two elements the function would return the sum of the list.
> This is what I have started with and I keep getting an error:
> (define (doall fn l)
>   (if (null? (cdr l)
>           (list (fn(car l)))
>           (append (process_all fn(cdr l))(list fn(car l))))))
> The error is this:
> if: bad syntax (has 1 part after keyword) in: (if (null? (cdr l) (list (fn
> (car l))) (append (process_all fn (cdr l)) (list fn (car l)))))
> I am trying to define the list with this function.  I suppose after I can
> get it to work, next I will work on the summation, product function.  First
> I need to get this list function to work.  Any ideas?
> Trista
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