Proposal: function which simulates C ?: operator

[Adal Chiriliuc]

I think a function similar to the one below should be added to the
builtin module:

def boolselect(cond ition, trueresult, falseresult):
if condition:
return trueresult
else:
return falseresult

--- WITH

scalewidth = boolselect(self .__vertical, _scalew, _scaleh)

a1 = 0
a4 = boolselect(self .__vertical, self.__width, self.__height)
a2 = (a4 - scalewidth) // 2
a3 = a2 + scalewidth

self.__meterwid th = self.__meterrec t[0].Width()
self.__meterhei ght = self.__meterrec t[0].Height()
self.__meterlen gth = boolselect(self .__vertical, self.__meterhei ght, self.__meterwid th)

t = boolselect(self .__range >= 18, -18, -12)
redzone = self.__dBToOffs et(-6)
yellowzone = self.__dBToOffs et(t)

--- WITHOUT

if self.__vertical :
scalewidth = _scalew
else:
scalewidth = _scaleh

a1 = 0
if self.__vertical :
a4 = self.__width
else:
a4 = self.__height
a2 = (a4 - scalewidth) // 2
a3 = a2 + scalewidth

self.__meterwid th = self.__meterrec t[0].Width()
self.__meterhei ght = self.__meterrec t[0].Height()
if self.__vertical :
self.__meterlen gth = self.__meterhei ght
else:
self.__meterlen gth = self.__meterwid th

if self.__range >= 18:
t = -18
else:
t = -12
redzone = self.__dBToOffs et(-6)
yellowzone = self.__dBToOffs et(t)

---

What do you think?

PS: maybe a better name than boolselect could be found.

[Dan Bishop]

"Mitja" <nu*@example.co m> wrote in message news:<LA******* ***********@new s.siol.net>...

Adal Chiriliuc <[e-mail] m>
(news:13******* *************** *@smtp.myrealbo x.com) wrote:

I think a function similar to the one below should be
added to the
builtin module:

def boolselect(cond ition, trueresult, falseresult):
if condition:
return trueresult
else:
return falseresult

--- WITH

scalewidth = boolselect(self .__vertical, _scalew, _scaleh)

--- WITHOUT

if self.__vertical :
scalewidth = _scalew
else:
scalewidth = _scaleh

What do you think?

Here's a nifty workaround I figured out myself but am sure others use it as
well:
scalewidth=(_sc aleh,_scalew)[__self.vertical]

If you're going to use the "(F, T)[C]" syntax, it would be better to
write it as "(F, T)[bool(C)]" to ensure that the array index is 0 or
1.

However, a better alternative is "(C and [T] or [F])[0]", which
short-circuits and also has the advantage of having the same order as
"if".

If you're absolutely certain that T will never be false, you can
simplify this to "C and T or F".

[Erik Max Francis]

Dan Bishop wrote:

However, a better alternative is "(C and [T] or [F])[0]", which
short-circuits and also has the advantage of having the same order as
"if".

It's got the same order, but it's completely opaque. It's hardly better
if you're interested in readability.

--
__ Erik Max Francis && ma*@alcyone.com && http://www.alcyone.com/max/
/ \ San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
\__/ Performing in front of a live audience is like a feeling of shock.
-- Sade Adu

[Reinhold Birkenfeld]

Peter Hansen wrote:

Adal Chiriliuc wrote:

I didn't know this was discussed so much in the past. I should have
searched before.
And if you read all of it, you probably wouldn't be making
the following suggestion, either. :-)

I now suggest that this function be added without implying that it's
the Python equivalent of ?: and with the docs clearly explaining that
it's not ?: and how it differs.

It won't happen because (a) it's a trivial function to write
on-demand,

How do you write this function without lambda in the call?
and (b) there are already several different ways of
spelling it with current Python syntax if you don't want a
function
One uglier than the other.
and (c) I suspect that the requirement for short-circuit
evaluation would actually be *more* common in Python than it
appears it is in C++ based on your very limited sample population.

ACK.

Reinhold

--
Wenn eine Linuxdistributi on so wenig brauchbare Software wie Windows
mitbrächte, wäre das bedauerlich. Was bei Windows der Umfang eines
"kompletten Betriebssystems " ist, nennt man bei Linux eine Rescuedisk.
-- David Kastrup in de.comp.os.unix .linux.misc

[Peter Hansen]

Reinhold Birkenfeld wrote:

Peter Hansen wrote:

It won't happen because (a) it's a trivial function to write
on-demand,

How do you write this function without lambda in the call?

Basically, you use if/then like you are "supposed" to. :-)
But the OP wasn't asking about a short-circuit version, just
the trivial fully evaluated function approach.

and (b) there are already several different ways of
spelling it with current Python syntax if you don't want a
function

One uglier than the other.

Agreed. Use if/then and save the sanity of your maintenance
programmers.

and (c) I suspect that the requirement for short-circuit
evaluation would actually be *more* common in Python than it
appears it is in C++ based on your very limited sample population.

ACK.

Ironic that Bill the Cat changed the meaning of that from
positive to negative. :-) (Or did he always use mixed-case,
so that all-caps ACK is still uniquely ASCII?)

-Peter

[Reinhold Birkenfeld]

Peter Hansen wrote:

Reinhold Birkenfeld wrote:

Peter Hansen wrote:

It won't happen because (a) it's a trivial function to write
on-demand,

How do you write this function without lambda in the call?

Basically, you use if/then like you are "supposed" to. :-)
But the OP wasn't asking about a short-circuit version, just
the trivial fully evaluated function approach.

Granted. This or (x and y or z) without y being false...

and (b) there are already several different ways of
spelling it with current Python syntax if you don't want a
function

One uglier than the other.

Agreed. Use if/then and save the sanity of your maintenance
programmers.

and (c) I suspect that the requirement for short-circuit
evaluation would actually be *more* common in Python than it
appears it is in C++ based on your very limited sample population.

ACK.

Ironic that Bill the Cat changed the meaning of that from
positive to negative. :-) (Or did he always use mixed-case,
so that all-caps ACK is still uniquely ASCII?)

Well, I don't know Bill the Cat, should I?

Reinhold

--
Wenn eine Linuxdistributi on so wenig brauchbare Software wie Windows
mitbrächte, wäre das bedauerlich. Was bei Windows der Umfang eines
"kompletten Betriebssystems " ist, nennt man bei Linux eine Rescuedisk.
-- David Kastrup in de.comp.os.unix .linux.misc

[Peter Hansen]

Reinhold Birkenfeld wrote:

Peter Hansen wrote:

Reinhold Birkenfeld wrote:

ACK.

Ironic that Bill the Cat changed the meaning of that from
positive to negative. :-) (Or did he always use mixed-case,
so that all-caps ACK is still uniquely ASCII?)

Well, I don't know Bill the Cat, should I?

Probably not. :-) It was a comic strip called "Bloom County"
which featured among many other things a cat named Bill who
was, uh, just a tad incoherent, and given to mutterings like
"Ack! Pthft!"

See http://encyclopedia.thefreedictionar...ll%20the%20Cat
for background, and the following for a nice pic:
http://www.premier.net/~cspedale/opus/images/bill2.jpg

-Peter