[plt-scheme] help writing idiomatic plt scheme

Just ignore my code above , i incorrectly read the problem statement.
Apologies to all.
Veer


On Mon, Jun 16, 2008 at 12:44 AM, Veer <diggerrrrr at gmail.com> wrote:
> I might as well try :
>
> ;;multi-filter : (string->boolean) port -> (list (listof string)
> (listof string) string)
> ;;to produce a list such that it simulates (list (filter f lst)
> (filter neg-f lst) extra)
> (define (multi-filter f in)
>  (local ((define (multi-filter-accum in L R S)
>            (local ((define a-line (read-line in)))
>              (cond
>                [(eof-object? a-line) (list L R S)]
>                [(f a-line) (multi-filter-accum in (cons  a-line L) R
>                                                (string-append S
> (substring a-line 0 1)))]
>                [else (multi-filter-accum in L (cons a-line R)
>                                          (string-append S (substring
> a-line 0 1)))]))))
>    (multi-filter-accum in empty empty "")))
>
> ;;expression
> (local ((define ALL (multi-filter (lambda (s) (char=? (string-ref s 0) #\#))
>                                        (open-input-file "line-ex")))
>        (define line-# (map (lambda (s) (substring s 1)) (first ALL)))
>        (define line-= (map (lambda (s) (substring s 1)) (second ALL)))
>        (define str-acc (third ALL)))
>  (list line-# line-= str-acc))
>
>
> If only  S could be somehow made optional or not reqd then
> multi-filter can be useful in other cases i guess.
>
> Veer
>