In article iok5tg$svv$1...@reader1.panix.com,
Grant Edwards invalid@invalid.invalid wrote:
On Tue, Apr 19, 2011 at 7:09 AM, Christian Heimes li...@cheimes.de wrote:
Am 18.04.2011 21:58, schrieb John Nagle:
?? ?? This is typical for languages which backed into a bool type,
rather than having
In article 9142usf51...@mid.individual.net,
Gregory Ewing greg.ew...@canterbury.ac.nz wrote:
Chris Angelico wrote:
Remind me some day to finish work on my ultimate programming
language, which starts out with a clean slate and lets the programmer
define his own operators and everything.
I'm not not touching you!
--
http://mail.python.org/mailman/listinfo/python-list
Albert van der Horst alb...@spenarnc.xs4all.nl wrote:
I guess I never thought about it, but there isn't an 'xor' operator to
go along with 'or' and 'and'. Must not be something I need very often.
There is. applied to booleans is xor.
Best to get into the habit of using '!=' otherwise
On Tue, Apr 19, 2011 at 7:09 AM, Christian Heimes li...@cheimes.de wrote:
Am 18.04.2011 21:58, schrieb John Nagle:
This is typical for languages which backed into a bool type,
rather than having one designed in. The usual result is a boolean
type with numerical semantics, like
True +
On Tue, Apr 19, 2011 at 4:23 PM, Kushal Kumaran
kushal.kumaran+pyt...@gmail.com wrote:
if a + b + c + d != 1:
raise ValueError(Exactly one of a, b, c or d must be true.)
Unless you're sure all of a, b, c, and d are boolean values, an int
with a negative value slipping in could result in
On Tue, 19 Apr 2011 16:26:50 +1000, Chris Angelico wrote:
On Tue, Apr 19, 2011 at 4:23 PM, Kushal Kumaran
kushal.kumaran+pyt...@gmail.com wrote:
if a + b + c + d != 1:
raise ValueError(Exactly one of a, b, c or d must be true.)
Unless you're sure all of a, b, c, and d are boolean
On Tue, Apr 19, 2011 at 6:43 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
but I don't see how
(arbitrary expression) + (another expression) + ... + (last expression)
can have any guarantees applied. I mean, you can't even guarantee that
they won't raise an exception. Can
On Tue, 2011-04-19 at 19:00 +1000, Chris Angelico wrote:
On Tue, Apr 19, 2011 at 6:43 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
but I don't see how
(arbitrary expression) + (another expression) + ... + (last expression)
can have any guarantees applied. I mean, you
On Tue, Apr 19, 2011 at 7:09 AM, Christian Heimes li...@cheimes.de wrote:
Am 18.04.2011 21:58, schrieb John Nagle:
?? ?? This is typical for languages which backed into a bool type,
rather than having one designed in. ??The usual result is a boolean
type with numerical semantics, like
??
On Apr 19, 10:23 am, Grant Edwards inva...@invalid.invalid wrote:
On Tue, Apr 19, 2011 at 7:09 AM, Christian Heimes li...@cheimes.de wrote:
Am 18.04.2011 21:58, schrieb John Nagle:
?? ?? This is typical for languages which backed into a bool type,
rather than having one designed in. ??The
Jean-Paul Calderone wrote:
Also boolean xor is the same as !=.
Only if you have booleans. Even without short circuiting,
a boolean xor operator could provide the service of
automatically booling things for you (is that a word?).
Jean-Paul
--
On Mon, Apr 18, 2011 at 3:49 PM, Chris Rebert c...@rebertia.com wrote:
Pro: You can do anything.
Con: You can do anything.
I think someone already beat you to it. They call their invention Lisp. :-P
Bah! Lisp comes, out of the box, with far too many features! No no no.
If you want the +
On Sun, 17 Apr 2011 22:49:41 -0700, Chris Rebert wrote:
Pro: You can do anything.
Con: You can do anything.
I think someone already beat you to it. They call their invention
Lisp. :-P
Also Forth.
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
On Apr 16, 1:24 pm, candide cand...@free.invalid wrote:
Consider the following code :
# --
def bool_equivalent(x):
return True if x else False
It's faster to write:
def bool_equivalent(x):
return not not x
Raymond
--
Le 18/04/2011 10:33, Raymond Hettinger a écrit :
# --
def bool_equivalent(x):
return True if x else False
It's faster to write:
def bool_equivalent(x):
return not not x
faster and ... smarter ;)
--
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote:
So in Python 2.2, Python introduced two new built-in names, True and
False, with values 1 and 0 respectively:
[steve@sylar ~]$ python2.2
Python 2.2.3 (#1, Aug 12 2010, 01:08:27)
[GCC 4.1.2 20070925 (Red Hat 4.1.2-27)] on linux2
On 4/17/2011 5:12 PM, Gregory Ewing wrote:
Chris Angelico wrote:
Well, of course you can always implement bool as an int;
Which Python used to do once upon a time -- and still does
in a way, because bool is a subclass of int.
The bool type was added mainly to provide a type that prints
out
John Nagle wrote:
Pascal got this right. (A nice feature of Pascal
was that packed array of boolean was a bit array).
C, which originally lacked a bool type, got it wrong.
So did Python.
If Python had had a boolean type from the beginning, it
probably wouldn't have been a subclass of int
Chris Angelico wrote:
Remind me some day to finish work on my ultimate programming
language, which starts out with a clean slate and lets the programmer
define his own operators and everything.
Didn't someone already do that and call it lisp? :-)
--
Greg
--
Am 18.04.2011 21:58, schrieb John Nagle:
This is typical for languages which backed into a bool type,
rather than having one designed in. The usual result is a boolean
type with numerical semantics, like
True + True
2
I find the behavior rather useful. It allows multi-xor tests
Le 17/04/2011 04:39, Ben Finney a écrit :
Why do you need to know? (I should have asked that question earlier.)
First because I was doubting the true interest of the bool() type. In
fact, it appears that it's _semantically_ a shortcut for
True if x else False. I could't imagine a builtin
On Sun, Apr 17, 2011 at 6:38 PM, candide candide@free.invalid wrote:
I also try to consider how essential the bool() type is.
Again compare with int() or str() types.
Well, of course you can always implement bool as an int; C has done
this for decades, and it hasn't killed it. You can also
candide candide@free.invalid writes:
First because I was doubting the true interest of the bool() type. In
fact, it appears that it's _semantically_ a shortcut for
True if x else False.
That bends my brain. Both ‘True’ and ‘False’ are instances of the ‘bool’
type. So of course the ‘bool’
On Sun, Apr 17, 2011 at 7:38 PM, candide candide@free.invalid wrote:
I could't imagine a builtin function having a so trivial implementation.
As it was pointed out, its not function, its type,
SETBUILTIN(bool, PyBool_Type);
While its __new__ is indeed trivial (in essence, it
Le 17/04/2011 11:46, Ben Finney a écrit :
candidecandide@free.invalid writes:
First because I was doubting the true interest of the bool() type. In
fact, it appears that it's _semantically_ a shortcut for
True if x else False.
That bends my brain. Both ‘True’ and ‘False’ are instances of
On Sun, Apr 17, 2011 at 8:38 AM, Ben Finney ben+pyt...@benfinney.id.au wrote:
It won't look up the *name* ‘bool’, but it will use that object. Any
boolean expression is going to be calling the built-in ‘bool’ type
constructor.
So the answer to the OP's question is no: the function isn't
candide candide@free.invalid writes:
Le 17/04/2011 11:46, Ben Finney a écrit :
What is the “shortcut” you refer to?
bool(x) is nothing more than a shortcut for the following expression :
True if x else False.
We're going around in circles. I've already pointed out that ‘bool(x)’
is what
candide wrote:
bool(x) is nothing more than a shortcut for the following expression :
True if x else False.
It's a much shorter and easier-to-read shortcut.
Also keep in mind that if-else expressions are quite a recent
addition to the language.
Before that, we had 'not not x' as another
Chris Angelico wrote:
Well, of course you can always implement bool as an int;
Which Python used to do once upon a time -- and still does
in a way, because bool is a subclass of int.
The bool type was added mainly to provide a type that prints
out as 'True' or 'False' rather than 1 or 0.
On Mon, 18 Apr 2011 01:22:59 +0200, candide wrote:
What is the
“shortcut” you refer to?
bool(x) is nothing more than a shortcut for the following expression :
True if x else False.
Nothing more? That's completely incorrect. bool is a type object, not
an expression, so you can do
Daniel Kluev dan.kl...@gmail.com writes:
Actually, as I was curious myself, I've checked sources and found that
`True if x else False` will _not_ call bool(), it calls
PyObject_IsTrue() pretty much directly.
Sure. By ‘bool(x)’ I'm referring only to the implementation inside that
constructor.
On Mon, Apr 18, 2011 at 10:22 AM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
types = [str, complex, float, bool]
[f(x) for f, x in zip(types, (1, 2, 3, 4))]
['1', (2+0j), 3.0, True]
I believe this one would work fine with a function defined as per OP -
zip takes callables,
On 01/-10/-28163 02:59 PM, Daniel Kluev wrote:
On Sun, Apr 17, 2011 at 8:38 AM, Ben Finneyben+pyt...@benfinney.id.au wrote:
It won't look up the *name* ‘bool’, but it will use that object. Any
boolean expression is going to be calling the built-in ‘bool’ type
constructor.
So the answer to the
On Mon, Apr 18, 2011 at 11:46 AM, Dave Angel da...@ieee.org wrote:
bool = int
Any language that allows you to do this is either awesome or
terrifying. Come to think of it, there's not a lot of difference.
Chris Angelico
--
http://mail.python.org/mailman/listinfo/python-list
On Mon, Apr 18, 2011 at 12:46 PM, Dave Angel da...@ieee.org wrote:
He didn't say that the function will call the bool() type (constructor), but
that it will use the bool type;
Actually, he did say exactly that
Any boolean expression is going to be _calling the built-in ‘bool’ type
Chris Angelico:
Dave Angel:
bool = int
Any language that allows you to do this is either awesome or
terrifying. Come to think of it, there's not a lot of difference.
Even better:
$ python2.7 -c 'False = True; print False'
True
Alas:
$ python3 -c 'False = True; print(False)'
File string,
On Mon, Apr 18, 2011 at 2:40 PM, Ned Deily n...@acm.org wrote:
Chris Angelico:
Dave Angel:
bool = int
Any language that allows you to do this is either awesome or
terrifying. Come to think of it, there's not a lot of difference.
Even better:
$ python2.7 -c 'False = True; print False'
On Sun, Apr 17, 2011 at 9:53 PM, Chris Angelico ros...@gmail.com wrote:
On Mon, Apr 18, 2011 at 2:40 PM, Ned Deily n...@acm.org wrote:
snip
Even better:
$ python2.7 -c 'False = True; print False'
True
http://bofh.ch/bofh/bofh13.html
Alas:
$ python3 -c 'False = True; print(False)'
File
Consider the following code :
# --
def bool_equivalent(x):
return True if x else False
# testing ...
def foo(x):
return 10*x
class C:
pass
for x in [42, (my,baby), baobab, max, foo, C] + [None, 0, , [],
{},()]:
print
On Sat, Apr 16, 2011 at 1:24 PM, candide candide@free.invalid wrote:
Consider the following code :
# --
def bool_equivalent(x):
return True if x else False
# testing ...
def foo(x):
return 10*x
class C:
pass
for x in [42, (my,baby),
candide candide@free.invalid writes:
Is the bool_equivalent() function really equivalent to the bool()
built-in function ?
The ‘bool’ built-in is not a function.
type(bool)
type 'type'
--
\ “Generally speaking, the errors in religion are dangerous; |
`\those in
Chris Rebert c...@rebertia.com writes:
That is, `True if x else False` conceptually gets compiled down to
`True if bool(x) == 1 else False` (but without doing a run-time lookup
of bool).
It won't look up the *name* ‘bool’, but it will use that object. Any
boolean expression is going to be
Le 16/04/2011 23:38, Ben Finney a écrit :
So the answer to the OP's question is no: the function isn't equivalent
to the type,
Can bool() type and bool_equivalent() function return different values ?
because the OP's ‘bool_equivalent’ function necessarily
uses the built-in ‘bool’ type,
Le 16/04/2011 23:13, Ben Finney a écrit :
The ‘bool’ built-in is not a function.
type(bool)
type 'type'
Oops, unfortunate confusion!! but built-in types and built-in functions
are sometimes so similar from the user's point of view ;)
All the same, you can notice that the
On Sat, Apr 16, 2011 at 4:51 PM, candide candide@free.invalid wrote:
Le 16/04/2011 23:38, Ben Finney a écrit :
So the answer to the OP's question is no: the function isn't equivalent
to the type,
Can bool() type and bool_equivalent() function return different values ?
No. The distinction
candide candide@free.invalid writes:
Le 16/04/2011 23:13, Ben Finney a écrit :
The ‘bool’ built-in is not a function.
Oops, unfortunate confusion!! but built-in types and built-in
functions are sometimes so similar from the user's point of view ;)
Yes, intentionally so, because:
All the
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