In article <4ca6bd15$0$2$c3e8...@news.astraweb.com>,
Steven D'Aprano wrote:
>On Fri, 01 Oct 2010 14:56:52 +0200, Antoon Pardon wrote:
>
>> Think about the following possibility.
>>
>> Someone provides you with a library of functions that act on sequences.
>> They rely on the fact that '+' con
On Oct 4, 3:09 pm, Gregory Ewing wrote:
> Carl Banks wrote:
> > Numpy uses + for elementwise addition, and a function
> > called concatenate for concatenation. If Python lists used a separate
> > concatenation operator, then Numpy arrays could use that for
> > concatenation.
>
> Actually it could
Carl Banks wrote:
Numpy uses + for elementwise addition, and a function
called concatenate for concatenation. If Python lists used a separate
concatenation operator, then Numpy arrays could use that for
concatenation.
Actually it couldn't, except for the special case of
concatenating along the
On Oct 4, 9:14 am, Ethan Furman wrote:
> Antoon Pardon wrote:
> > Suppose you write your class so that '+' will provide addition and
> > you provide a method concat to concatenate. Now no matter how usefull
> > the sequence library would be for you, you can't use it. You will
> > have to rewrite t
On 10/2/2010 8:36 AM, Carl Banks wrote:
On Oct 1, 9:38 pm, Steven D'Aprano wrote:
If so, then we haven't gained anything, and the only thing that would
satisfy such people would be for every function name and operator to be
unique -- something which is impossible in practice, even if it were
de
Antoon Pardon wrote:
Suppose you write your class so that '+' will provide addition and
you provide a method concat to concatenate. Now no matter how usefull
the sequence library would be for you, you can't use it. You will
have to rewrite those function you need, in terms of a concat method
inst
On Sat, Oct 02, 2010 at 05:03:17AM +, Steven D'Aprano wrote:
> On Fri, 01 Oct 2010 14:56:52 +0200, Antoon Pardon wrote:
>
> > Think about the following possibility.
> >
> > Someone provides you with a library of functions that act on sequences.
> > They rely on the fact that '+' concatenates.
On Fri, Oct 01, 2010 at 09:44:34AM -0700, Emile van Sebille wrote:
> On 10/1/2010 5:56 AM Antoon Pardon said...
>
> >Someone provides you with a library of functions that act on sequences.
> >They rely on the fact that '+' concatenates.
> >
> >Someone else provides you with a library of functions
On Sat, Oct 02, 2010 at 04:38:16AM +, Steven D'Aprano wrote:
> On Fri, 01 Oct 2010 10:24:11 -0700, Carl Banks wrote:
>
> > On Sep 26, 8:20 am, Grant Edwards wrote:
> [..]
> >> So now I suppose "+" for string concatenation is a bad thing.
> >
> > Yes. It's not the end of the world, but a sep
Stefan Schwarzer a écrit :
> One could argue that using L[::-1] isn't "obvious"
It *is* obvious - once you've learned slicing. "obvious" doesn't mean
you shouldn't bother reading the FineManual.
--
http://mail.python.org/mailman/listinfo/python-list
Seebs wrote:
> On 2010-10-03, Steven D'Aprano
> wrote:
>> On Sat, 02 Oct 2010 12:50:02 -0700, Dennis Lee Bieber wrote:
>>> Well... We could maybe borrow from REXX... and
>>> use || for concatenation.
>
>>|| for concatenation? What's the connection between the pipe character
>> and c
On 2010-10-03, Steven D'Aprano wrote:
> On Sat, 02 Oct 2010 12:50:02 -0700, Dennis Lee Bieber wrote:
>> Well... We could maybe borrow from REXX... and
>> use || for concatenation.
>|| for concatenation? What's the connection between the pipe character
> and concatenation?
Th
On Sat, 02 Oct 2010 12:50:02 -0700, Dennis Lee Bieber wrote:
> Well... We could maybe borrow from REXX... and
> use || for concatenation.
|| for concatenation? What's the connection between the pipe character
and concatenation? I realise that, ultimately, every symbol was
On Sat, 02 Oct 2010 14:09:15 -0700, geremy condra wrote:
> I'd actually love the ability to overload this, although I'm not sold on
> the itertools.chain thing. To me it looks a lot like the 'is isomorphic'
> operator from graph theory, and we could really use that in Graphine.
You can overload t
On Sat, 02 Oct 2010 14:12:39 -0700, Dennis Lee Bieber wrote:
> I'd prefer to see it used for floating point comparison in the two
> character:
> x ~= y
> though one might need to set up some system parameter to define what the
> permissible delta would be...
>
> sys.fl
On 02/10/2010 22:12, Dennis Lee Bieber wrote:
On Sat, 02 Oct 2010 21:24:19 +0100, MRAB
declaimed the following in gmane.comp.python.general:
How about "~", which is currently has only a unary form:
>>> "foo" ~ "bar"
'foobar'
>>> [1, 2, 3] ~ [4, 5, 6]
[1, 2, 3, 4, 5, 6]
Think of it as me
On Sat, Oct 2, 2010 at 1:24 PM, MRAB wrote:
> On 02/10/2010 20:50, Dennis Lee Bieber wrote:
>>
>> On 02 Oct 2010 04:38:16 GMT, Steven D'Aprano
>> declaimed the following in
>> gmane.comp.python.general:
>>
>>
>>> If so, then we haven't gained anything, and the only thing that would
>>> satisfy s
On 02/10/2010 20:50, Dennis Lee Bieber wrote:
On 02 Oct 2010 04:38:16 GMT, Steven D'Aprano
declaimed the following in
gmane.comp.python.general:
If so, then we haven't gained anything, and the only thing that would
satisfy such people would be for every function name and operator to be
uniqu
On Oct 1, 9:38 pm, Steven D'Aprano wrote:
> If so, then we haven't gained anything, and the only thing that would
> satisfy such people would be for every function name and operator to be
> unique -- something which is impossible in practice, even if it were
> desirable.
That is the ideal, yes, a
On Fri, 01 Oct 2010 14:56:52 +0200, Antoon Pardon wrote:
> Think about the following possibility.
>
> Someone provides you with a library of functions that act on sequences.
> They rely on the fact that '+' concatenates.
>
> Someone else provides you with a library of functions that act on
> num
On Fri, 01 Oct 2010 10:24:11 -0700, Carl Banks wrote:
> On Sep 26, 8:20 am, Grant Edwards wrote:
[..]
>> So now I suppose "+" for string concatenation is a bad thing.
>
> Yes. It's not the end of the world, but a separate concatenation
> operator would have been better. Then there's no temptat
On Sep 26, 8:20 am, Grant Edwards wrote:
> On 2010-09-26, Paul Rubin wrote:
>
> > Steven D'Aprano writes:
> >> There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
> > Why would it not be ["spam","spam","spam"] or even "ssspppaaammm"?
>
> Because
>
> 3 * "spam" == "spam" + "sp
On 10/1/2010 9:44 AM Emile van Sebille said...
On 10/1/2010 5:56 AM Antoon Pardon said...
Someone provides you with a library of functions that act on sequences.
They rely on the fact that '+' concatenates.
Someone else provides you with a library of functions that act on
numbers. They rely on
On 10/1/2010 5:56 AM Antoon Pardon said...
Someone provides you with a library of functions that act on sequences.
They rely on the fact that '+' concatenates.
Someone else provides you with a library of functions that act on
numbers. They rely on the fact that '+' provides addition.
But you
On Thu, Sep 30, 2010 at 07:02:40AM -0700, Emile van Sebille wrote:
> On 9/30/2010 5:10 AM Antoon Pardon said...
> >On Sun, Sep 26, 2010 at 03:20:18PM +, Grant Edwards wrote:
> >>On 2010-09-26, Paul Rubin wrote:
> >>>Steven D'Aprano writes:
> There's nothing obscure or unintuitive about "s
On 9/30/2010 5:10 AM Antoon Pardon said...
On Sun, Sep 26, 2010 at 03:20:18PM +, Grant Edwards wrote:
On 2010-09-26, Paul Rubin wrote:
Steven D'Aprano writes:
There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
Why would it not be ["spam","spam","spam"] or even "ss
On Sun, Sep 26, 2010 at 03:20:18PM +, Grant Edwards wrote:
> On 2010-09-26, Paul Rubin wrote:
> > Steven D'Aprano writes:
> >> There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
>
> > Why would it not be ["spam","spam","spam"] or even "ssspppaaammm"?
>
> Because
>
>
On 2010-09-29, Lawrence D'Oliveiro wrote:
> In message , Seebs wrote:
>> Helps, perhaps, that I got exposed to group theory early enough to be used
>> to redefining + and * to be any two operations which have interesting
>> properties ...
> But groups only have one such operation; it???s rings an
In message , Seebs wrote:
> Helps, perhaps, that I got exposed to group theory early enough to be used
> to redefining + and * to be any two operations which have interesting
> properties ...
But groups only have one such operation; it’s rings and fields (and number
systems) that have two.
--
h
On Sun, 26 Sep 2010 09:30:08 +, Seebs wrote:
>> There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
>> and the fact that it doesn't do the same thing as int("spam")*3 is a
>> foolish argument.
>
> The languages in which it's surprising are mostly things like perl,
> where
On Sun, 26 Sep 2010 01:16:49 -0700, Paul Rubin wrote:
> Steven D'Aprano writes:
>> There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
> Why would it not be ["spam","spam","spam"] or even "ssspppaaammm"?
The first one would be a reasonable design choice, although less useful
Paul Rubin writes:
> Seebs writes:
>> * It seems clear that, given two sequences x and y, "x + y" ought to
>> be the concatenation of these sequences.
>>...
>> Helps, perhaps, that I got exposed to group theory early enough to be used
>> to redefining + and * to be any two operations which hav
On 9/26/2010 1:16 AM, Paul Rubin wrote:
Steven D'Aprano writes:
There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
Why would it not be ["spam","spam","spam"] or even "ssspppaaammm"?
Should "spam"*2.5 be "spamspamsp"?
Should "spam"-"a" be "spm"? What about "spamspam"-"a"?
Grant Edwards wrote:
> On 2010-09-26, Paul Rubin wrote:
>> Steven D'Aprano writes:
>>> There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
>
>> Why would it not be ["spam","spam","spam"] or even "ssspppaaammm"?
>
> Because
>
> 3 * "spam" == "spam" + "spam" + "spam"
>
> Ju
On 2010-09-26, Paul Rubin wrote:
> Steven D'Aprano writes:
>> There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
> Why would it not be ["spam","spam","spam"] or even "ssspppaaammm"?
Because
3 * "spam" == "spam" + "spam" + "spam"
Just like
3 * 6 = 6 + 6 + 6
So now I su
meaningful symantics.
Simply put, a sequence multiplied by -1 can give a reversed sequence.
Then for any sequence "seq", and integer n>0, we can have
"seq * -n" producing "(seq * -1) * n".
Any thoughts?
Gimmicky.
Best to define multiplication only by unsign
On 26/09/2010 07:27, Steven D'Aprano wrote:
I'm surprised that you think that you
should be able to apply arbitrary mathematical operations to strings
*before* turning them into an int and still get sensible results. That
boggles my mind.
You clearly have not been "spoiled rotten" by php.
Seebs writes:
> * It seems clear that, given two sequences x and y, "x + y" ought to
> be the concatenation of these sequences.
>...
> Helps, perhaps, that I got exposed to group theory early enough to be used
> to redefining + and * to be any two operations which have interesting
> properties*.
On 2010-09-26, Steven D'Aprano wrote:
> On Sat, 25 Sep 2010 23:46:57 -0700, Paul Rubin wrote:
>> I think the idea is you should not be able to do mathematical operations
>> on strings, and if you try to do one, Python should raise an exception,
>> rather than using hokey analogies to guess at what
Steven D'Aprano writes:
> There's nothing obscure or unintuitive about "spam"*3 = "spamspamspam",
Why would it not be ["spam","spam","spam"] or even "ssspppaaammm"?
Should "spam"*2.5 be "spamspamsp"?
Should "spam"-"a" be "spm"? What about "spamspam"-"a"?
And what about "spam"/2? "sp" be an ok
On Sat, 25 Sep 2010 23:46:57 -0700, Paul Rubin wrote:
> Steven D'Aprano writes:
>> I'm surprised that you think that you should be able to apply arbitrary
>> mathematical operations to strings *before* turning them into an int
>> and still get sensible results. That boggles my mind.
>
> I think
Steven D'Aprano writes:
> I'm surprised that you think that you should be able to apply
> arbitrary mathematical operations to strings *before* turning them
> into an int and still get sensible results. That boggles my mind.
I think the idea is you should not be able to do mathematical operations
On Sat, 25 Sep 2010 22:08:54 -0700, John Nagle wrote:
> On 9/25/2010 4:45 AM, Thomas Jollans wrote:
>> On Saturday 25 September 2010, it occurred to Yingjie Lan to exclaim:
>>> Hi,
>>>
>>> I noticed that in python3k, multiplying a sequence by a negative
>>> integer is the same as multiplying it by
On 9/25/2010 4:45 AM, Thomas Jollans wrote:
On Saturday 25 September 2010, it occurred to Yingjie Lan to exclaim:
Hi,
I noticed that in python3k, multiplying a sequence by a negative integer is
the same as multiplying it by 0, and the result is an empty sequence. It
seems to me that there is a
Hi all,
Thanks for considering this proposal seriously and
all your discussions shed light on the pro's and cons
(well, more cons than pros, to be honest).
It occurrs to me that this proposal is not a sound
one, for the reasons already well documented in
this thread, which I need not repeat.
On Sat, 25 Sep 2010 06:54:36 -0700, Yingjie Lan wrote:
> For the rule above, how about the
> case to reverse and multiply:
>
L*-3 #L reversed and repeated three times
>
> v.s.
>
L[::-1]*3 #L reversed and repeated three times
>
> The first one is simpler (4 chars v.s. 9 chars). I thou
d.
Since lists of negative length don't exist, we're free to set the
invariance to something which has a less restrictive domain and is more
useful than raising an exception:
for every list l and integer n:
len(l*n) == len(l)*max(0, n)
>> Simply put, a sequence multiplied by -
On 25 Sep, 09:22, Yingjie Lan wrote:
> Hi,
>
> I noticed that in python3k, multiplying a sequence by a negative integer is
> the same as multiplying it by 0, and the result is an empty sequence. It
> seems to me that there is a more meaningful symantics.
>
> Simply put, a s
Hi Terry,
On 2010-09-25 19:24, Terry Reedy wrote:
> On 9/25/2010 4:22 AM, Yingjie Lan wrote:
> There is already a builtin reversed() function whose output can be
> multiplied.
Seemingly, it can't:
$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type "help
On 9/25/2010 10:24 AM Terry Reedy said...
On 9/25/2010 4:22 AM, Yingjie Lan wrote:
I noticed that in python3k, multiplying a sequence by a negative
integer is the same as multiplying it by 0, and the result is an
empty sequence.
This is explicitly documented: "Values of n less than 0 are treat
empty sequence of the same type as s).) I would have
made this raise a ValueError, but someone must have had a use case for
getting an empty sequence.
It seems to me that there is a more meaningful symantics.
Simply put, a sequence multiplied by -1 can give a reversed
sequence.
There is alre
Stefan Schwarzer wrote:
> On 2010-09-25 15:54, Yingjie Lan wrote:
>> The first one is simpler (4 chars v.s. 9 chars).
>> I thought it was also intuitive because if you multiply
>> a vector by -1, you should get a vector
>> in the reversed direction. But, intuitiveness depends
>> on who you are, wh
Hi,
On 2010-09-25 15:54, Yingjie Lan wrote:
> The first one is simpler (4 chars v.s. 9 chars).
One thing is whether a certain form is shorter, another
thing to take into account is how often you need the
functionality.
> I thought it was also intuitive because if you multiply
> a vector by -1, y
Hi,
>
> In my opinion this _isn't_ a situation where it's good. :)
>
> L[::-1]
>
> is only marginally longer than
>
> -1 * L
>
> I think this small gain doesn't justify "violating" this
> "Python Zen" rule (from `import this`):
>
> There should be one-- and preferably only one
>
Hi,
On 2010-09-25 14:11, Yingjie Lan wrote:
> Having more than one way of doing things sometimes is good.
In my opinion this _isn't_ a situation where it's good. :)
L[::-1]
is only marginally longer than
-1 * L
I think this small gain doesn't justify "violating" this
"Python Zen" rule
len(l*n) == len(l) * abs(n),
which is also broken under current python3k.
if you think len(..) as a mathematical norm,
the above invariance makes perfect sense:
|| a * b || == ||a|| * |b|, b is real
>
> > Simply put, a sequence multiplied by -1 can give a
> reversed sequence.
>
>
benefits
for the operation to succeed for any integer operand.
>
> Simply put, a sequence multiplied by -1 can give a reversed sequence.
For that, we have slicing. A negative step value produces a reverse slice of
the list. You can't argue that this makes sense, can you
&g
Hi,
I noticed that in python3k, multiplying a sequence by a negative integer is the
same as multiplying it by 0, and the result is an empty sequence. It seems to
me that there is a more meaningful symantics.
Simply put, a sequence multiplied by -1 can give a reversed sequence.
Then for any
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