* Element-Relative Sequence Insertion
@ 2009-06-11 12:11 Nordlöw
2009-06-11 12:38 ` Pascal J. Bourguignon
0 siblings, 1 reply; 8+ messages in thread
From: Nordlöw @ 2009-06-11 12:11 UTC (permalink / raw
To: help-gnu-emacs
How do I insert an element (object) relative to another in a sequence
(or list in my case)? Example:
(insert-after 'X '(a b c) 'b) => '(a b X c)
(insert-before 'X '(a b c) b) => '(a X b c)
Thanks in advance,
Nordlöw
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Element-Relative Sequence Insertion
2009-06-11 12:11 Element-Relative Sequence Insertion Nordlöw
@ 2009-06-11 12:38 ` Pascal J. Bourguignon
2009-06-11 12:51 ` Nordlöw
0 siblings, 1 reply; 8+ messages in thread
From: Pascal J. Bourguignon @ 2009-06-11 12:38 UTC (permalink / raw
To: help-gnu-emacs
Nordlöw <per.nordlow@gmail.com> writes:
> How do I insert an element (object) relative to another in a sequence
> (or list in my case)? Example:
>
> (insert-after 'X '(a b c) 'b) => '(a b X c)
> (insert-before 'X '(a b c) b) => '(a X b c)
This is not what you want. You don't what these function to return a
2-element lists, the first of which is the symbol quote. Unless
you're doing meta-programming you never want to have such a result.
You wan this:
(insert-after 'X '(a b c) 'b) --> (a b X c)
(insert-before 'X '(a b c) 'b) --> (a X b c)
Also, you may want to mention whether your insert-after and
insert-before function are destructive or non-destructive. Since you
show as only specification examples using literal data, we will assume
you want them to be non-destructive.
So you do that, just by doing it. There's nothing simplier.
\f
(qrsha vafreg-nsgre (arj yvfg byq)
(pbaq ((ahyy yvfg) '())
((rdy byq (pne yvfg)) (pbaf (pne yvfg) (pbaf arj (pqe yvfg))))
(g (pbaf (pne yvfg) (vafreg-nsgre arj (pqe yvfg) byq)))))
(qrsha vafreg-orsber (arj yvfg byq)
(pbaq ((ahyy yvfg) '())
((rdy byq (pne yvfg)) (pbaf arj yvfg))
(g (pbaf (pne yvfg) (vafreg-orsber arj (pqe yvfg) byq)))))
--
__Pascal Bourguignon__
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Element-Relative Sequence Insertion
2009-06-11 12:38 ` Pascal J. Bourguignon
@ 2009-06-11 12:51 ` Nordlöw
2009-06-11 13:01 ` Pascal J. Bourguignon
0 siblings, 1 reply; 8+ messages in thread
From: Nordlöw @ 2009-06-11 12:51 UTC (permalink / raw
To: help-gnu-emacs
On 11 Juni, 14:38, p...@informatimago.com (Pascal J. Bourguignon)
wrote:
> Nordlöw <per.nord...@gmail.com> writes:
> > How do I insert an element (object) relative to another in a sequence
> > (or list in my case)? Example:
>
> > (insert-after 'X '(a b c) 'b) => '(a b X c)
> > (insert-before 'X '(a b c) b) => '(a X b c)
>
> This is not what you want. You don't what these function to return a
> 2-element lists, the first of which is the symbol quote. Unless
> you're doing meta-programming you never want to have such a result.
>
> You wan this:
>
> (insert-after 'X '(a b c) 'b) --> (a b X c)
> (insert-before 'X '(a b c) 'b) --> (a X b c)
>
> Also, you may want to mention whether your insert-after and
> insert-before function are destructive or non-destructive. Since you
> show as only specification examples using literal data, we will assume
> you want them to be non-destructive.
>
> So you do that, just by doing it. There's nothing simplier.
>
> (qrsha vafreg-nsgre (arj yvfg byq)
> (pbaq ((ahyy yvfg) '())
> ((rdy byq (pne yvfg)) (pbaf (pne yvfg) (pbaf arj (pqe yvfg))))
> (g (pbaf (pne yvfg) (vafreg-nsgre arj (pqe yvfg) byq)))))
>
> (qrsha vafreg-orsber (arj yvfg byq)
> (pbaq ((ahyy yvfg) '())
> ((rdy byq (pne yvfg)) (pbaf arj yvfg))
> (g (pbaf (pne yvfg) (vafreg-orsber arj (pqe yvfg) byq)))))
>
> --
> __Pascal Bourguignon__
But how do I implement insert-after() and insert-before()? I guess the
code in the end doesn't do anything meaningful :)
/Nordlöw
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Element-Relative Sequence Insertion
2009-06-11 12:51 ` Nordlöw
@ 2009-06-11 13:01 ` Pascal J. Bourguignon
2009-06-11 14:18 ` Marc Tfardy
0 siblings, 1 reply; 8+ messages in thread
From: Pascal J. Bourguignon @ 2009-06-11 13:01 UTC (permalink / raw
To: help-gnu-emacs
Nordlöw <per.nordlow@gmail.com> writes:
> On 11 Juni, 14:38, p...@informatimago.com (Pascal J. Bourguignon)
> wrote:
>> Nordlöw <per.nord...@gmail.com> writes:
>> > How do I insert an element (object) relative to another in a sequence
>> > (or list in my case)? Example:
>>
>> > (insert-after 'X '(a b c) 'b) => '(a b X c)
>> > (insert-before 'X '(a b c) b) => '(a X b c)
>>
>> This is not what you want. You don't what these function to return a
>> 2-element lists, the first of which is the symbol quote. Unless
>> you're doing meta-programming you never want to have such a result.
>>
>> You wan this:
>>
>> (insert-after 'X '(a b c) 'b) --> (a b X c)
>> (insert-before 'X '(a b c) 'b) --> (a X b c)
>>
>> Also, you may want to mention whether your insert-after and
>> insert-before function are destructive or non-destructive. Since you
>> show as only specification examples using literal data, we will assume
>> you want them to be non-destructive.
>>
>> So you do that, just by doing it. There's nothing simplier.
>>
>> (qrsha vafreg-nsgre (arj yvfg byq)
>> (pbaq ((ahyy yvfg) '())
>> ((rdy byq (pne yvfg)) (pbaf (pne yvfg) (pbaf arj (pqe yvfg))))
>> (g (pbaf (pne yvfg) (vafreg-nsgre arj (pqe yvfg) byq)))))
>>
>> (qrsha vafreg-orsber (arj yvfg byq)
>> (pbaq ((ahyy yvfg) '())
>> ((rdy byq (pne yvfg)) (pbaf arj yvfg))
>> (g (pbaf (pne yvfg) (vafreg-orsber arj (pqe yvfg) byq)))))
>>
>> --
>> __Pascal Bourguignon__
>
> But how do I implement insert-after() and insert-before()? I guess the
> code in the end doesn't do anything meaningful :)
It does, but you have to decrypt it first.
Could you implement first something simplier than insert-after or
insert-before?
For example, could you implement a function map, which builds a new
list with the result of calling a function to each element of a list:
(defun map (function list) ...)
(map (lambda (x) (1+ x)) '(1 2 3)) --> (2 3 4)
(map (lambda (x) (1+ x)) '()) --> ()
If you can do that, then you should be able to implement
insert-before and insert-after adding only one line.
--
__Pascal Bourguignon__
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Element-Relative Sequence Insertion
2009-06-11 13:01 ` Pascal J. Bourguignon
@ 2009-06-11 14:18 ` Marc Tfardy
2009-06-11 14:36 ` Pascal J. Bourguignon
0 siblings, 1 reply; 8+ messages in thread
From: Marc Tfardy @ 2009-06-11 14:18 UTC (permalink / raw
To: help-gnu-emacs
Pascal J. Bourguignon schrieb:
> Nordlöw <per.nordlow@gmail.com> writes:
>
>> On 11 Juni, 14:38, p...@informatimago.com (Pascal J. Bourguignon)
>> wrote:
>>> Nordlöw <per.nord...@gmail.com> writes:
>>>> How do I insert an element (object) relative to another in a sequence
>>>> (or list in my case)? Example:
>>>> (insert-after 'X '(a b c) 'b) => '(a b X c)
>>>> (insert-before 'X '(a b c) b) => '(a X b c)
>>> This is not what you want. You don't what these function to return a
>>> 2-element lists, the first of which is the symbol quote. Unless
>>> you're doing meta-programming you never want to have such a result.
>>>
>>> You wan this:
>>>
>>> (insert-after 'X '(a b c) 'b) --> (a b X c)
>>> (insert-before 'X '(a b c) 'b) --> (a X b c)
>>>
>>> Also, you may want to mention whether your insert-after and
>>> insert-before function are destructive or non-destructive. Since you
>>> show as only specification examples using literal data, we will assume
>>> you want them to be non-destructive.
>>>
>>> So you do that, just by doing it. There's nothing simplier.
>>>
>>> (qrsha vafreg-nsgre (arj yvfg byq)
>>> (pbaq ((ahyy yvfg) '())
>>> ((rdy byq (pne yvfg)) (pbaf (pne yvfg) (pbaf arj (pqe yvfg))))
>>> (g (pbaf (pne yvfg) (vafreg-nsgre arj (pqe yvfg) byq)))))
>>>
>>> (qrsha vafreg-orsber (arj yvfg byq)
>>> (pbaq ((ahyy yvfg) '())
>>> ((rdy byq (pne yvfg)) (pbaf arj yvfg))
>>> (g (pbaf (pne yvfg) (vafreg-orsber arj (pqe yvfg) byq)))))
>>>
>>> --
>>> __Pascal Bourguignon__
>> But how do I implement insert-after() and insert-before()? I guess the
>> code in the end doesn't do anything meaningful :)
>
> It does, but you have to decrypt it first.
(defun insert-after (elt lst new)
(cond ((null lst)
'())
((eq new (car lst))
(cons (car lst) (cons elt (cdr lst))))
(t
(cons (car lst) (insert-after elt (cdr lst) new)))))
(defun insert-before (elt lst new)
(cond ((null lst)
'())
((eq new (car lst))
(cons elt lst))
(t
(cons (car lst) (insert-before elt (cdr lst) new)))))
What is the price? ;-)
regards
Marc
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Element-Relative Sequence Insertion
2009-06-11 14:18 ` Marc Tfardy
@ 2009-06-11 14:36 ` Pascal J. Bourguignon
2009-06-11 15:01 ` Marc Tfardy
2009-06-13 16:47 ` Johan Bockgård
0 siblings, 2 replies; 8+ messages in thread
From: Pascal J. Bourguignon @ 2009-06-11 14:36 UTC (permalink / raw
To: help-gnu-emacs
Marc Tfardy <bum@cyk.cyk> writes:
> Pascal J. Bourguignon schrieb:
>> Nordlöw <per.nordlow@gmail.com> writes:
>>
>>> On 11 Juni, 14:38, p...@informatimago.com (Pascal J. Bourguignon)
>>> wrote:
>>>> Nordlöw <per.nord...@gmail.com> writes:
>>>>> How do I insert an element (object) relative to another in a sequence
>>>>> (or list in my case)? Example:
>>>>> (insert-after 'X '(a b c) 'b) => '(a b X c)
>>>>> (insert-before 'X '(a b c) b) => '(a X b c)
>>>> This is not what you want. You don't what these function to return a
>>>> 2-element lists, the first of which is the symbol quote. Unless
>>>> you're doing meta-programming you never want to have such a result.
>>>>
>>>> You wan this:
>>>>
>>>> (insert-after 'X '(a b c) 'b) --> (a b X c)
>>>> (insert-before 'X '(a b c) 'b) --> (a X b c)
>>>>
>>>> Also, you may want to mention whether your insert-after and
>>>> insert-before function are destructive or non-destructive. Since you
>>>> show as only specification examples using literal data, we will assume
>>>> you want them to be non-destructive.
>>>>
>>>> So you do that, just by doing it. There's nothing simplier.
>>>>
>>>> (defun insert-after (new list old)
>>>> (cond ((null list) '())
>>>> ((eql old (car list)) (cons (car list) (cons new (cdr list))))
>>>> (t (cons (car list) (insert-after new (cdr list) old)))))
>>>>
>>>> (defun insert-before (new list old)
>>>> (cond ((null list) '())
>>>> ((eql old (car list)) (cons new list))
>>>> (t (cons (car list) (insert-before new (cdr list) old)))))
>>>>
>>>> --
>>>> __Pascal Bourguignon__
>>> But how do I implement insert-after() and insert-before()? I guess the
>>> code in the end doesn't do anything meaningful :)
>>
>> It does, but you have to decrypt it first.
>
> (defun insert-after (elt lst new)
> (cond ((null lst)
> '())
> ((eq new (car lst))
> (cons (car lst) (cons elt (cdr lst))))
> (t
> (cons (car lst) (insert-after elt (cdr lst) new)))))
>
> (defun insert-before (elt lst new)
> (cond ((null lst)
> '())
> ((eq new (car lst))
> (cons elt lst))
> (t
> (cons (car lst) (insert-before elt (cdr lst) new)))))
>
> What is the price? ;-)
What's the point in renaming the parameters and introducing bugs?
Check again the order of the parameters!
Notice that (eq 3.141592 3.141592) --> nil ; which is the reason why
eql should be used by default.
And bad points for not being able to use rot13.
You lose. :-)
--
__Pascal Bourguignon__
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Element-Relative Sequence Insertion
2009-06-11 14:36 ` Pascal J. Bourguignon
@ 2009-06-11 15:01 ` Marc Tfardy
2009-06-13 16:47 ` Johan Bockgård
1 sibling, 0 replies; 8+ messages in thread
From: Marc Tfardy @ 2009-06-11 15:01 UTC (permalink / raw
To: help-gnu-emacs
>>> It does, but you have to decrypt it first.
>> (defun insert-after (elt lst new)
>> (cond ((null lst)
>> '())
>> ((eq new (car lst))
>> (cons (car lst) (cons elt (cdr lst))))
>> (t
>> (cons (car lst) (insert-after elt (cdr lst) new)))))
>>
>> (defun insert-before (elt lst new)
>> (cond ((null lst)
>> '())
>> ((eq new (car lst))
>> (cons elt lst))
>> (t
>> (cons (car lst) (insert-before elt (cdr lst) new)))))
>>
>> What is the price? ;-)
>
> What's the point in renaming the parameters and introducing bugs?
>
> Check again the order of the parameters!
OK, this was a mistake. But it's "only" cosmetics ;-) I tested this
with:
(insert-after 'X '(a b c) 'b)
(a b X c)
(insert-before 'X '(a b c) 'b)
(a X b c)
so I unintended assumed your right arguments order ;)
> Notice that (eq 3.141592 3.141592) --> nil ; which is the reason why
> eql should be used by default.
Yes, this was my big fault. Sorry.
> And bad points for not being able to use rot13.
>
> You lose. :-)
Oh shit... :-)
regards
Marc
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Element-Relative Sequence Insertion
2009-06-11 14:36 ` Pascal J. Bourguignon
2009-06-11 15:01 ` Marc Tfardy
@ 2009-06-13 16:47 ` Johan Bockgård
1 sibling, 0 replies; 8+ messages in thread
From: Johan Bockgård @ 2009-06-13 16:47 UTC (permalink / raw
To: help-gnu-emacs
pjb@informatimago.com (Pascal J. Bourguignon) writes:
> Notice that (eq 3.141592 3.141592) --> nil ; which is the reason why
> eql should be used by default.
The normal equality predicate for Emacs Lisp is `equal'.
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2009-06-13 16:47 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-06-11 12:11 Element-Relative Sequence Insertion Nordlöw
2009-06-11 12:38 ` Pascal J. Bourguignon
2009-06-11 12:51 ` Nordlöw
2009-06-11 13:01 ` Pascal J. Bourguignon
2009-06-11 14:18 ` Marc Tfardy
2009-06-11 14:36 ` Pascal J. Bourguignon
2009-06-11 15:01 ` Marc Tfardy
2009-06-13 16:47 ` Johan Bockgård
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