Re: [Chicken-users] read file into a list of lists

[Jinsong Liang]

Hi Arthur,

I need a list of lists because each line has more than one number. You first solution works for me. All I need to do is to add an extra string-split call, which returns a list.

Thanks a lot!

Jinsong

On Tue, Jul 12, 2016 at 11:52 PM, Arthur Maciel <address@hidden> wrote:

Although I can't imagine why you'd need it, but in order to get list of lists you could do:

(define (read-all-lines filename)
   (with-input-from-file filename
      (lambda ()
         (map (lambda (x)
                       (list (string->number x)))
                    (read-lines)))))

I'm not sure that's what you want.

Cheers,

Arthur

On Wed, Jul 13, 2016 at 12:49 AM, Jinsong Liang <address@hidden> wrote:

Hi Arthur,

This simplifies my code a lot! I will give it a try.

Thank you!

Jinsong

On Tue, Jul 12, 2016 at 11:45 PM, Arthur Maciel <address@hidden> wrote:

Jinsong, the closest solution I can think of is the read-lines procedure, which returns a list of strings (each string a line read).

http://api.call-cc.org/doc/extras/read-lines

Supposing you have a number per line, you could use string->number to get the result.

An example would be:

(define (read-all-lines filename)

   (with-input-from-file filename

      (lambda ()

         (map string->number (read-lines)))))

Cheers,

Arthur

On Wed, Jul 13, 2016 at 12:07 AM, Jinsong Liang <address@hidden> wrote:

Hi,

I need to read a file (lines of numbers) into a list of lists with each line a list. I wrote the following function to do it:

(define (read-all-lines file-name)
 (let ([output '()])
   (let ([p (open-input-file file-name)])
     (let f ([x (read-line p)])
       (if (eof-object? x)
         (close-input-port p)
         (begin
           (set! output (cons (string-split x) output))
           (f (read-line p))))))
   (reverse output)))

I have a few questions regarding the above code:

1. Is there an existing API to do the same thing?

2. Using set! seems not a lispy coding style. Is it true?

3. Any improvements I can make ? I bet there are tons.

Thank you!

Jinsong

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