Hello,

I have an ASCII file that gets written by some other (non-lispy) process
and contains (a known number of) integers, one per line, e.g. like this:

8
7 7
5

Now I want to read these numbers into a list, so that instead of
hard-coding the numbers like

(let ((my-list (list 8 7 7 5)))
(do-something-with-the-list))

I can have something like

(let ((my-list (unknown-code-to-read-from-an-include-file)))
(do-something-with-the-list))

Unfortunately, I have no elegant solution how
"unknown-code-to-read-from-an-include-file" should look (in Common Lisp
or Emacs Lisp). The best I could come up with is

(require 'f) ; An Emacs library for file handling
(let ((my-list (mapcar #'string-to-number
(split-string (f-read "ascii-file.el")))))
(do-something-with-the-list))

"f-read" returns a string, so I need to convert into a list of strings
and then into a list of numbers. Works, but looks clumsy.

A simple "load-file" will not do, since it just returns T (for successful
reading), not the three integer numbers read, so "my-list" is no list,
but the truthiness value.

Any ideas?

Best regards

Axel

Axel Reichert <mail@axel-reichert.de> writes:

> Hello,
>
> I have an ASCII file that gets written by some other (non-lispy) process
> and contains (a known number of) integers, one per line, e.g. like this:
>
> 8
> 7
> 7
> 5
>
> Now I want to read these numbers into a list, so that instead of
> hard-coding the numbers like
>
> (let ((my-list (list 8 7 7 5)))
> (do-something-with-the-list))
>
> I can have something like
>
> (let ((my-list (unknown-code-to-read-from-an-include-file)))
> (do-something-with-the-list))
>
> Unfortunately, I have no elegant solution how
> "unknown-code-to-read-from-an-include-file" should look (in Common Lisp
> or Emacs Lisp). The best I could come up with is
>
> (require 'f) ; An Emacs library for file handling
> (let ((my-list (mapcar #'string-to-number
> (split-string (f-read "ascii-file.el")))))
> (do-something-with-the-list))
>
> "f-read" returns a string, so I need to convert into a list of strings
> and then into a list of numbers. Works, but looks clumsy.
>
> A simple "load-file" will not do, since it just returns T (for successful
> reading), not the three integer numbers read, so "my-list" is no list,
> but the truthiness value.
>
> Any ideas?
>
> Best regards
>
> Axel

Something like this, perhaps?

(defun read-numbers-from-file (file-path)
(with-open-file (f file-path :direction :input)
(loop for line = (read-line f nil)
while line
collect (parse-integer line))))

Axel Reichert <mail@axel-reichert.de> writes:

> Hello,
>
> I have an ASCII file that gets written by some other (non-lispy) process
> and contains (a known number of) integers, one per line, e.g. like this:
>
> 8
> 7
> 7
> 5
>
> Now I want to read these numbers into a list, so that instead of
> hard-coding the numbers like
>
> (let ((my-list (list 8 7 7 5)))
> (do-something-with-the-list))
>
> I can have something like
>
> (let ((my-list (unknown-code-to-read-from-an-include-file)))
> (do-something-with-the-list))
>
> Unfortunately, I have no elegant solution how
> "unknown-code-to-read-from-an-include-file" should look (in Common Lisp
> or Emacs Lisp). The best I could come up with is
>
> (require 'f) ; An Emacs library for file handling
> (let ((my-list (mapcar #'string-to-number
> (split-string (f-read "ascii-file.el")))))
> (do-something-with-the-list))
>
> "f-read" returns a string, so I need to convert into a list of strings
> and then into a list of numbers. Works, but looks clumsy.
>
> A simple "load-file" will not do, since it just returns T (for successful
> reading), not the three integer numbers read, so "my-list" is no list,
> but the truthiness value.
>
> Any ideas?

The task seems straightforward and it looks you solved it. It will look
a lot better if you abstract your strategy away in a procedure. So your
code will look like

(do-something-with (file->list-of-numbers "ascii.file.txt")).

I don't much ELISP, but we might not be too far off with

(defun file->list-of-numbers (fname)
(mapcar #'string-to-number
(split-string (f-read fname))))

On Mon, 18 Dec 2023 19:00:22 +0100
Axel Reichert <mail@axel-reichert.de> wrote:
> Hello,
>
> I have an ASCII file that gets written by some other (non-lispy) process
> and contains (a known number of) integers, one per line, e.g. like this:
>
> 8
> 7
> 7
> 5
>
> Now I want to read these numbers into a list, so that instead of
> hard-coding the numbers like
>
> (let ((my-list (list 8 7 7 5)))
> (do-something-with-the-list))
>
> I can have something like
>
> (let ((my-list (unknown-code-to-read-from-an-include-file)))
> (do-something-with-the-list))

[...]

> A simple "load-file" will not do, since it just returns T (for successful
> reading), not the three integer numbers read, so "my-list" is no list,
> but the truthiness value.

Actually LOAD returns T for successful *evaluation* .In your example , it
read and evaluated each of the forms 8 , 7 , 7 , 5 .Each of those evaluates
to itself [i.e. the respective number] so obviously the evaluation was
successful.

I will give a modified version of the code in
<m234vztlqv.fsf@MacBook-Pro-2.home> because I don't like LOOP .

(defun read-numbers-from-file
(file-path non ; non = number of numbers
&aux (vec (make-array non)))
(with-open-file (f file-path :direction :input)
(dotimes (i non (map 'list (function identity) vec))
(let ((num (read f nil)))
(unless num (error "Wrong number of numbers in the file"))
(setf (aref vec i) num)))))

If you decide that you'd rather have the numbers in a vector rather than
in a list , it's trivial to modify the above code to get that.

--
What is deadly is a language community that is /not/ delighted with its
language and itself.
Kenny Tilton
groups.google.com/d/msg/comp.lang.lisp/Ege9MyXRvH4/Y5mpGo4BKQkJ

Spiros Bousbouras <spibou@gmail.com> writes:

> On Mon, 18 Dec 2023 19:00:22 +0100
> Axel Reichert <mail@axel-reichert.de> wrote:
>> Hello,
>>
>> I have an ASCII file that gets written by some other (non-lispy) process
>> and contains (a known number of) integers, one per line, e.g. like this:
>>
>> 8
>> 7
>> 7
>> 5
>>
>> Now I want to read these numbers into a list, so that instead of
>> hard-coding the numbers like
>>
>> (let ((my-list (list 8 7 7 5)))
>> (do-something-with-the-list))
>>
>> I can have something like
>>
>> (let ((my-list (unknown-code-to-read-from-an-include-file)))
>> (do-something-with-the-list))
>
> [...]
>
>> A simple "load-file" will not do, since it just returns T (for successful
>> reading), not the three integer numbers read, so "my-list" is no list,
>> but the truthiness value.
>
> Actually LOAD returns T for successful *evaluation* .In your example , it
> read and evaluated each of the forms 8 , 7 , 7 , 5 .Each of those evaluates
> to itself [i.e. the respective number] so obviously the evaluation was
> successful.
>
> I will give a modified version of the code in
> <m234vztlqv.fsf@MacBook-Pro-2.home> because I don't like LOOP .
>
> (defun read-numbers-from-file
> (file-path non ; non = number of numbers
> &aux (vec (make-array non)))
> (with-open-file (f file-path :direction :input)
> (dotimes (i non (map 'list (function identity) vec))
> (let ((num (read f nil)))
> (unless num (error "Wrong number of numbers in the file"))
> (setf (aref vec i) num)))))
>
> If you decide that you'd rather have the numbers in a vector rather than
> in a list , it's trivial to modify the above code to get that.

For people who don't like extended loop, I think this a better
implementation:

(defun read-numbers-from-file/2 (file-path n)
(with-open-file (f file-path :direction :input)
(let ((res nil))
(dotimes (i n)
(push (parse-integer (read-line f nil)) res))
(nreverse res))))

* Julieta Shem <87jzpb74lq.fsf@ yaxenu.org> :
Wrote on Mon, 18 Dec 2023 15:22:41 -0300:
> Axel Reichert <mail @axel-reichert.de> writes:
>> I have an ASCII file that gets written by some other (non-lispy) process
>> and contains (a known number of) integers, one per line, e.g. like this:
>>
>> 8
>> 7
>> 7
>> 5
>>
>> Now I want to read these numbers into a list, so that instead of
>> hard-coding the numbers like
>>
>> (let ((my-list (list 8 7 7 5)))
>> (do-something-with-the-list))
>>
<snip>
>> (require 'f) ; An Emacs library for file handling
>> (let ((my-list (mapcar #'string-to-number
>> (split-string (f-read "ascii-file.el")))))
>> (do-something-with-the-list))
>>
>> "f-read" returns a string, so I need to convert into a list of strings
>> and then into a list of numbers. Works, but looks clumsy.
>>
>> A simple "load-file" will not do, since it just returns T (for successful
>> reading), not the three integer numbers read, so "my-list" is no list,
>> but the truthiness value.
>>
>> Any ideas?
>
> The task seems straightforward and it looks you solved it. It will look
> a lot better if you abstract your strategy away in a procedure. So your
> code will look like
>
> (do-something-with (file->list-of-numbers "ascii.file.txt")).
>
> I don't much ELISP, but we might not be too far off with
>
> (defun file->list-of-numbers (fname)
> (mapcar #'string-to-number
> (split-string (f-read fname))))

In elisp, for the specific case where Axel controls the file being read
it may be as simple to leverage the lisp reader.

(car (read-from-string (concat "(" (f-read "file.txt") ")")))

(with-temp-buffer
(insert "(")
(insert-file-contents "/dev/shm/barf")
(goto-char (point-max))
(insert ")")
(goto-char (point-min))
(read (current-buffer)))

Madhu <enometh@meer.net> writes:

> (car (read-from-string (concat "(" (f-read "file.txt") ")")))

Nice, thanks! I had found "read-from-string", but could not come up with
the idea to create a Lisp expression.

Best regards

Axel

Julieta Shem <jshem@yaxenu.org> writes:

> The task seems straightforward and it looks you solved it. It will look
> a lot better if you abstract your strategy away in a procedure. So your
> code will look like
>
> (do-something-with (file->list-of-numbers "ascii.file.txt")).

Yes, sure, that is better. Thanks!

Axel

Raymond Wiker <rwiker@gmail.com> writes:

> For people who don't like extended loop,

.... count me in.

> (defun read-numbers-from-file/2 (file-path n)
> (with-open-file (f file-path :direction :input)
> (let ((res nil))
> (dotimes (i n)
> (push (parse-integer (read-line f nil)) res))
> (nreverse res))))

Yes, that will be the Common Lisp version. Thanks to you, too!

Axel

Spiros Bousbouras <spibou@gmail.com> writes:

>> A simple "load-file" will not do, since it just returns T (for successful
>> reading), not the three integer numbers read, so "my-list" is no list,
>> but the truthiness value.
>
> Actually LOAD returns T for successful *evaluation* .In your example , it
> read and evaluated each of the forms 8 , 7 , 7 , 5 .Each of those evaluates
> to itself [i.e. the respective number] so obviously the evaluation was
> successful.

Yes, sure, my formulation was too short for still being precise. I meant
to state it like you did above. Thanks for the clarification.

Best regards

Axel