Re: Using append to create a list from a line of text

Re: Using append to create a list from a line of text

[Pascal J. Bourguignon]

acomber <deedexy@gmail.com> writes:

> I want to create a list of words from a line of text delimitted by tabs. I
> want to basically split the line into atoms, split by tab.
>
> The code below is sort of pseudocode but is this the best approach to do
> this type of thing?
>
> Here is my first attempt:-
>
> (defun get-hdr()
>     ;obviously point must be positioned on correct line
>     (let (mylist)
>       while(not (end-of-line)
>          while(re-search-forward ("[A-Za-z]+[^\t\n]" nil t)
>            append (match-string 1) mylist      
>          )
>       )
>    )
> )

Nice, but it's not formatted correctly.  I'd avise you to use
paredit-mode.

Adding and removing newlines where one should, and letting emacs indent
the sexp, we get this text:


    (defun get-hdr()
      ;; obviously point must be positioned on correct line
      (let (mylist)
        while
        (not (end-of-line)
             while
             (re-search-forward ("[A-Za-z]+[^\t\n]" nil t)
                                append
                                (match-string 1)
                                mylist))))

Now, two obvious things:

1- undefined variable named `while'.  Where does that variable come
   from?

2- the function `not' is passed three arguments, when it expects only
   one!

3- "[A-Za-z]+[^\t\n]" is not a symbol naming an operator, nor is it a
   lambda expression, therefore the sexp ("[A-Za-z]+[^\t\n]" nil t) is
   not a lisp form.

4- undefined avariable named `append'.

5- while re-search-forward takes optionally up to four arguments, I
   doubt that mylist is bound to the count of searches to do, or that
   (match-string 1) returns whether you want or not to signal errors if
   no match is found.


> How do I get my function to return the list, mylist?

Try to read a lisp tutorial again.  On the first chapter, the basic
syntactic elements are always presented.  You should have no problem
understanding them and correcting your code.


-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
A bad day in () is better than a good day in {}.

Re: Using append to create a list from a line of text

[Barry Margolin]

In article <87ip3m6vyj.fsf@kuiper.lan.informatimago.com>,
 "Pascal J. Bourguignon" <pjb@informatimago.com> wrote:

> acomber <deedexy@gmail.com> writes:
> 
> > I want to create a list of words from a line of text delimitted by tabs. I
> > want to basically split the line into atoms, split by tab.
> >
> > The code below is sort of pseudocode but is this the best approach to do
> > this type of thing?
> >
> > Here is my first attempt:-
> >
> > (defun get-hdr()
> >     ;obviously point must be positioned on correct line
> >     (let (mylist)
> >       while(not (end-of-line)
> >          while(re-search-forward ("[A-Za-z]+[^\t\n]" nil t)
> >            append (match-string 1) mylist      
> >          )
> >       )
> >    )
> > )
> 
> Nice, but it's not formatted correctly.  I'd avise you to use
> paredit-mode.
> 
> Adding and removing newlines where one should, and letting emacs indent
> the sexp, we get this text:
> 
> 
>     (defun get-hdr()
>       ;; obviously point must be positioned on correct line
>       (let (mylist)
>         while
>         (not (end-of-line)
>              while
>              (re-search-forward ("[A-Za-z]+[^\t\n]" nil t)
>                                 append
>                                 (match-string 1)
>                                 mylist))))
> 
> Now, two obvious things:
> 
> 1- undefined variable named `while'.  Where does that variable come
>    from?
> 
> 2- the function `not' is passed three arguments, when it expects only
>    one!

I think you missed that he said this was pseudo-code, not valid Lisp 
code.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Re: Using append to create a list from a line of text

[Pascal J. Bourguignon]

Barry Margolin <barmar@alum.mit.edu> writes:

> In article <87ip3m6vyj.fsf@kuiper.lan.informatimago.com>,
>  "Pascal J. Bourguignon" <pjb@informatimago.com> wrote:
>
>> acomber <deedexy@gmail.com> writes:
>> 
>> > I want to create a list of words from a line of text delimitted by tabs. I
>> > want to basically split the line into atoms, split by tab.
>> >
>> > The code below is sort of pseudocode but is this the best approach to do
>> > this type of thing?
>> >
>> > Here is my first attempt:-
>> >
>> > (defun get-hdr()
>> >     ;obviously point must be positioned on correct line
>> >     (let (mylist)
>> >       while(not (end-of-line)
>> >          while(re-search-forward ("[A-Za-z]+[^\t\n]" nil t)
>> >            append (match-string 1) mylist      
>> >          )
>> >       )
>> >    )
>> > )
>> 
>> Nice, but it's not formatted correctly.  I'd avise you to use
>> paredit-mode.
>> 
>> Adding and removing newlines where one should, and letting emacs indent
>> the sexp, we get this text:
>> 
>> 
>>     (defun get-hdr()
>>       ;; obviously point must be positioned on correct line
>>       (let (mylist)
>>         while
>>         (not (end-of-line)
>>              while
>>              (re-search-forward ("[A-Za-z]+[^\t\n]" nil t)
>>                                 append
>>                                 (match-string 1)
>>                                 mylist))))
>> 
>> Now, two obvious things:
>> 
>> 1- undefined variable named `while'.  Where does that variable come
>>    from?
>> 
>> 2- the function `not' is passed three arguments, when it expects only
>>    one!
>
> I think you missed that he said this was pseudo-code, not valid Lisp 
> code.

Indeed, I missed it.  But also, if you write your pseudo code as a
possibly valid lisp form, you can easily make it executable:

http://groups.google.com/group/comp.lang.lisp/msg/a827235ce7466a92

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
A bad day in () is better than a good day in {}.

Using append to create a list from a line of text

[acomber]

I want to create a list of words from a line of text delimitted by tabs. I
want to basically split the line into atoms, split by tab.

The code below is sort of pseudocode but is this the best approach to do
this type of thing?

Here is my first attempt:-

(defun get-hdr()
    ;obviously point must be positioned on correct line
    (let (mylist)
      while(not (end-of-line)
         while(re-search-forward ("[A-Za-z]+[^\t\n]" nil t)
           append (match-string 1) mylist      
         )
      )
   )
)

How do I get my function to return the list, mylist?




--
View this message in context: http://emacs.1067599.n5.nabble.com/Using-append-to-create-a-list-from-a-line-of-text-tp283808.html
Sent from the Emacs - Help mailing list archive at Nabble.com.

Re: Using append to create a list from a line of text

[Christopher Schmidt]

acomber <deedexy@gmail.com> writes:
> I want to create a list of words from a line of text delimitted by
> tabs. I want to basically split the line into atoms, split by tab.

    (save-restriction
      (narrow-to-region (line-beginning-position) (line-end-position))
      (split-string (buffer-string) "\t+"))

> The code below is sort of pseudocode but is this the best approach to
> do this type of thing?
[...]
> How do I get my function to return the list, mylist?

    M-: (info "(eintr)Top") RET

        Christopher

RE: Using append to create a list from a line of text

[Drew Adams]

> I want to create a list of words from a line of text 
> delimitted by tabs. I want to basically split the line
> into atoms, split by tab.

C-h f split-string