Asp Forum - a few thoughts for ruby...

Roger Pack

4/11/2009 4:53:00 AM

Thought I'd pass these thoughts by the readers here before sending them
to core. They're my current wish list :)

1) add an Object#in? method to complement the existing Array#include?

2) add some useful lists of exceptions, ex: IO.SELECT_EXCEPTIONS,
IO.READ_EXCEPTIONS, so that you can rescue the wide gamut of them
appropriately, should you desire to.

3) provide an easier way to know which platform you're on than
RUBY_PLATFORM =~ /mswin32|dgjpp|mingw/

4) (this one's controversial) remove the extra # for code in strings
(i.e. "string#{code}") -> "string{code}" less typing.

5) add a BigDecimal(float) method.
-> BigDecimal.new("%f" % float)

6) add Dir.directory?
-> File.directory?

Feedback?
Thanks!
-=r
--
Posted via http://www.ruby-....

22 Answers

Joel VanderWerf

4/11/2009 5:22:00 AM

Roger Pack wrote:
> Thought I'd pass these thoughts by the readers here before sending them
> to core. They're my current wish list :)
>
> 1) add an Object#in? method to complement the existing Array#include?

It's not really symmetrical. Array has an #include? method because it is
a collection. Object has #in? because it is--what? A potential member of
a collection?

This would conflict with lots of potential other uses of #in? that have
nothing to do with collections:

Clutch#in?

Doctor#in?

Fix#in?

(to start just with the 0-ary ones).

> 2) add some useful lists of exceptions, ex: IO.SELECT_EXCEPTIONS,
> IO.READ_EXCEPTIONS, so that you can rescue the wide gamut of them
> appropriately, should you desire to.

I've wanted that, and ended up with:

ALL_NETWORK_ERRORS = [Errno::ECONNRESET, Errno::ECONNABORTED,
Errno::ECONNREFUSED, Errno::EPIPE, IOError, Errno::ETIMEDOUT]

ALL_NETWORK_ERRORS << Errno::EPROTO if defined?(Errno::EPROTO)
ALL_NETWORK_ERRORS << Errno::ENETUNREACH if defined?(Errno::ENETUNREACH)

Maybe a better way would be to include a module, AnyNetworkError, in
each of these. Then you could

rescue AnyNetworkError

Like this:

module E; end

class E1 < StandardError; include E; end
class E2 < StandardError; include E; end

begin
raise E1, "foo"
rescue E => ex
p ex
end

> 4) (this one's controversial) remove the extra # for code in strings
> (i.e. "string#{code}") -> "string{code}" less typing.

Would not like having to escape { in strings...

--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

Roger Pack

4/11/2009 6:31:00 AM

Thanks for the reply Joel.

>> 1) add an Object#in? method to complement the existing Array#include?
>
> It's not really symmetrical. Array has an #include? method because it is
> a collection. Object has #in? because it is--what? A potential member of
> a collection?

Yeah. I'm not saying it's symmetric as much as useful and
intuitive--some of the big reasons I like Ruby :)
Would #within? be better?

> I've wanted that, and ended up with:
>
> ALL_NETWORK_ERRORS = [Errno::ECONNRESET, Errno::ECONNABORTED,
> Errno::ECONNREFUSED, Errno::EPIPE, IOError, Errno::ETIMEDOUT]
>
> ALL_NETWORK_ERRORS << Errno::EPROTO if defined?(Errno::EPROTO)
> ALL_NETWORK_ERRORS << Errno::ENETUNREACH if defined?(Errno::ENETUNREACH)

Looks like it would indeed be useful--especially for cross platform
where you 'wish you didnt have to know them all for every platform'
(there really are a lot of them -- see
http://betterlogic.com/rog... as an example).

> Maybe a better way would be to include a module, AnyNetworkError, in
> each of these. Then you could...

Yeah, or have them all descend from a single ancestor. I would say just
descend from SocketError except that SocketError is actually raised as
an exception itself, every so often, so it has its own meaning
currently...though I guess that doesn't stop it from being an ancestor.

> module E; end
...
> begin
> raise E1, "foo"
> rescue E => ex
> p ex
> end

That's pretty elegant. With an array you can [non intuitively] also get
by:

> begin
> raise SocketError "foo"
> rescue *ALL_NETWORK_ERRORS => ex
> p ex
> end
(I'm sure you knew that).

>> 4) (this one's controversial) remove the extra # for code in strings
>> (i.e. "string#{code}") -> "string{code}" less typing.
>
> Would not like having to escape { in strings...

Ok. This next isn't meant as an attacking question but...do you use { in
normal strings often? Granted probably more than #, but...?

Thanks!
-=r
--
Posted via http://www.ruby-....

Nobuyoshi Nakada

4/11/2009 7:03:00 AM

Hi,

At Sat, 11 Apr 2009 15:30:54 +0900,
Roger Pack wrote in [ruby-talk:333612]:
> Ok. This next isn't meant as an attacking question but...do you use { in
> normal strings often? Granted probably more than #, but...?

gettext, and printf in 1.9.

printf "%{foo}\n", foo:1 #=> 1

--
Nobu Nakada

Robert Klemme

4/11/2009 8:42:00 AM

On 11.04.2009 06:52, Roger Pack wrote:
> Thought I'd pass these thoughts by the readers here before sending them
> to core. They're my current wish list :)
>
> 1) add an Object#in? method to complement the existing Array#include?

-0

I don't see the benefit but I'm also not strongly against. I do see
Joel's point about the reversion. Basically it is strange that every
object should be able to answer a question that only the collection can
answer. Plus, you can easily add it yourself if you need it.

> 2) add some useful lists of exceptions, ex: IO.SELECT_EXCEPTIONS,
> IO.READ_EXCEPTIONS, so that you can rescue the wide gamut of them
> appropriately, should you desire to.

A good idea. But I do not know how feasible this is. Not all OS have
the same error reporting mechanisms and the mapping from OS errors to
exception types would have to be maintained of all platforms.

> 3) provide an easier way to know which platform you're on than
> RUBY_PLATFORM =~ /mswin32|dgjpp|mingw/

-1

This would make a Ruby specific unification of operating systems
necessary. This means that not only maintainers of automake need to
keep track of operating systems but also maintainers of Ruby. Other
difficulties are: how much level of detail do you provide? For one
application it may be enough to know it's running on Linux, the other
one needs to know the kernel version and a third one does not bother
about versions but must know the distro. I see too much effort for too
little benefit.

> 4) (this one's controversial) remove the extra # for code in strings
> (i.e. "string#{code}") -> "string{code}" less typing.

-1

Definitively a don't as the overhead of typing # isn't too big (plus, it
is more easily spotted) and the potential for damage caused by this is
large.

> 5) add a BigDecimal(float) method.
> -> BigDecimal.new("%f" % float)

0

Seems reasonable at first sight but the absence might have a reason.
For example, by making the conversion to String explicit it is more
obvious that float and BigDecimal are not really compatible.

> 6) add Dir.directory?
> -> File.directory?

0

Btw, there is also this nice idiom for those tests

if test ?d, "some dir"

Kind regards

robert

Nobuyoshi Nakada

4/11/2009 9:52:00 AM

Hi,

At Sat, 11 Apr 2009 13:52:49 +0900,
Roger Pack wrote in [ruby-talk:333607]:
> 6) add Dir.directory?
> -> File.directory?

Dir.exist? exists in 1.9.

--
Nobu Nakada

Roger Pack

4/11/2009 6:43:00 PM

>> 1) add an Object#in? method to complement the existing Array#include?
>
> -0
>
> I don't see the benefit but I'm also not strongly against. I do see
> Joel's point about the reversion. Basically it is strange that every
> object should be able to answer a question that only the collection can
> answer. Plus, you can easily add it yourself if you need it.

I kind of agree with Joel on this one, too.

A few other observations:

re: in?
Currently with #select you've got one in Kernel [which is IO.select] but
Arrays seem to have their own #select. So it is "conceivably possible"
to have a "default #in?" and have it overridden by Clutch#in? or
House#in? if desired.

Another option would be included? -- might be more ruby-y :)

>> 2) add some useful lists of exceptions, ex: IO.SELECT_EXCEPTIONS,
>> IO.READ_EXCEPTIONS, so that you can rescue the wide gamut of them
>> appropriately, should you desire to.
>
> A good idea. But I do not know how feasible this is. Not all OS have
> the same error reporting mechanisms and the mapping from OS errors to
> exception types would have to be maintained of all platforms.

True, mapping exceptions directly from OS to OS would be problematic.
And knowing which ones are on each OS is also annoying.
I am proposing more of a (platform dependent) container of all possible
exceptions, regardless of what they may mean. Or have them all include
a common ancestor--same result.

>> 3) provide an easier way to know which platform you're on than
>> RUBY_PLATFORM =~ /mswin32|dgjpp|mingw/
>
> -1
>
> This would make a Ruby specific unification of operating systems
> necessary. This means that not only maintainers of automake need to
> keep track of operating systems but also maintainers of Ruby. Other
> difficulties are: how much level of detail do you provide? For one
> application it may be enough to know it's running on Linux, the other
> one needs to know the kernel version and a third one does not bother
> about versions but must know the distro. I see too much effort for too
> little benefit.

True maintaining this is annoying, but I'd also propose that it's
useful. Currently in 1.9 we have:
>> RUBY_VERSION
=> "1.9.2"
>> RUBY_PLATFORM
=> "x86_64-linux"
>> RUBY_ENGINE
=> "ruby"

Typically "enough" OS information is given in RUBY_PLATFORM to determine
the platform--it's just "hard" to use that for such. My example being
that knowing if you're on windows is something like RUBY_PLATFORM =~
/dgjpp|mingw|mswin/
which seems overly complex for me. And very hard to get right the first
time (ex: RUBY_PLATFORM =~ /win/ doesn't work--that includes darwin).

>> 4) (this one's controversial) remove the extra # for code in strings
>> (i.e. "string#{code}") -> "string{code}" less typing.
>
> -1
>
> Definitively a don't as the overhead of typing # isn't too big (plus, it
> is more easily spotted) and the potential for damage caused by this is
> large.

True it's not too hard to type--I just think its absence would be less
typing, and that the # is "too" easily spotted, but again, that's just
my take on it. Actually you may have a reasonable point (easy to spot
is good).

The kicker is also that # is ingrained so much in existing ruby
code...it would be a pretty dramatic change.

>> 5) add a BigDecimal(float) method.
>> -> BigDecimal.new("%f" % float)
>
> 0
>
> Seems reasonable at first sight but the absence might have a reason.
> For example, by making the conversion to String explicit it is more
> obvious that float and BigDecimal are not really compatible.

Yeah I wonder that myself. I was just hoping to make it easier to use
BigDecimal, since Floats are so imprecise to use for decimal numbers :)

> if test ?d, "some dir"

Could you explain that again? Not sure I do understand the idiom.
Looks like bash?
Much thanks.
-=r
--
Posted via http://www.ruby-....

Colin Bartlett

4/11/2009 8:35:00 PM

>> Roger Pack
>>
>> Thought I'd pass these thoughts by the readers here before sending them
>> to core. They're my current wish list :)
>>
>> 1) add an Object#in? method to complement the existing Array#include?

> Joel VanderWerf
>
> It's not really symmetrical. Array has an #include? method because it is
> a collection. Object has #in? because it is--what? A potential member of
> a collection?

> Robert Klemme
>
> I don't see the benefit but I'm also not strongly against. I do see
> Joel's point about the reversion. Basically it is strange that every
> object should be able to answer a question that only the collection can
> answer. Plus, you can easily add it yourself if you need it.

Sometimes the best (or better) usage depends on the context.
For example, on some occasions we use: Integer === object
and on other occasions we use: object.kind_of?( Integer )
So I'm not against this on principle, and for me the question is
what is the balance between not adding things unless we need to
and does this make things easier in a significant number of cases.
I don't know the answer!

>> Roger Pack
>> 4) (this one's controversial) remove the extra # for code in strings
>> (i.e. "string#{code}") -> "string{code}" less typing.

I'm not in favour, for Robert Klemme's reasons.

>>> Roger Pack
>>>
>>> 5) add a BigDecimal(float) method.
>>> -> BigDecimal.new("%f" % float)

>> Robert Klemme
>>
>> Seems reasonable at first sight but the absence might have a reason.
>> For example, by making the conversion to String explicit it is more
>> obvious that float and BigDecimal are not really compatible.

> Roger Pack
>
> Yeah I wonder that myself. I was just hoping to make it easier to use
> BigDecimal, since Floats are so imprecise to use for decimal numbers :)

Then probably best to start with BigDecimal and keep using it?
We can always use BD = BigDecimal ; BD.new( "123.456" )
and I seem to recall that there's a way to assign a method to a variable
which could reduce this to BD( "123.456" ). I think it's important
to normally use strings to get BigDecimal values to avoid precision errors.

Robert Klemme makes a good point: Float has less precision than BigDecimal
and in general I think that you should be *very* wary about converting
from lower precision to higher precision - at least not without being
fully aware of what you are doing - because later on you may be mislead
into thinking that your calculation is more accurate than it actually is.
(See "Here's one I made earlier" below.)

You can't gain precision by such a conversion, which is why my start
position is not to do it. That said, converting Float to BigDecimal
may sometimes be useful when it can prevent further loss of precision.
For example, ( float_a - float_b ) can reduce the accuracy drastically,
and conversion to BigDecimal might be useful there.
( Caveat: Numerical Analysis - study of ... - can be extremely tricky,
and I only know enough about it to know that:
1. I don't understand it sufficiently to make definitive statements.
2. In my own stuff I probably ignore it more than I should. )

So I am against easy conversion by using something like BigDecimal( float ).
I think any standard conversion method from Float to BigDecimal
should be relatively ugly and messy. I did tbink of suggesting a rather long
method name, maybe BigDecimal.do_you_really_want_to_convert_this_float(fnum)
but someone can always alias that to a much shorter name.

If you require "bigdecimal/util" this does, amongst other things:
# BigDecimal utility library. ... The following methods are provided
# to convert other types to BigDecimals: ...
class Float < Numeric
def to_d
BigDecimal(self.to_s)
end
end

So you can require that library, or just use BigDecimal( float.to_s ),
I think BigDecimal( float.to_s ) satisfies my general thought here
that whatever the conversion method used is, it shouldn't be so simple
that you can use it without being in some way being reminded
that what you are doing might not be a good idea.
So making it sort of ugly fits in with that.
(In fact, I'm not sure that having a Float#to_d method is a good idea.)

Doing a quick bit of testing suggested that using "%f" % float
might be better than using float.to_s because in some cases
the former preserves information that is actually in the float
which the latter uses. In fact, I was going to suggest you propose
to use "%f" % self in Float#to_d instead of self.to_s.
But after some more thought and a bit of testing, I found that
for me in IRB "%f" % float only gives results to 6 decimal places
but float.to_s seems to give results to 14 or 15 significant figures
so overall using float.to_s for the conversion seems better.

If we want a BigDecimal method (and in view of BigDecimal( float.to_s )
I don't think we do - but BigDecimal( float.to_s ) should perhaps
be mentioned prominently in BigDecimal documentation)
how about something like (not tested):
def BigDecimal.from_f( f )
if f.kind_of?( Float ) then BigDecimal( f.to_s )
else raise "BigDecimal.from_f: argument must be a Float"
end
end

An argument for this is that by providing it you give a reasonably
simple standard way to do it which might reduce potentially
problematic "build your own" solutions.
(I'm not against "build your own" in principle: at the least
it can be a useful way to find out how things work,
and it may result in an improvement, and as long as it's
your own time and your own decision to do it, why not?
But where there are hidden pitfalls, a reliable and
reasonably easy to use solution is a good idea.)

***** For those who want to know a bit more *****

*** Here's one I made earlier. ***

(Really! Two days ago, in fact. For those not in the UK the reference
is to a long-running BBC television programme for children:
http://en.wikipedia.org/wiki/...
... The show is also famous for its "makes", which are demonstrations
of how to construct a useful object or prepare food. These have given rise
to the oft-used phrase "Here's one I made earlier", as presenters bring out
a perfect and completed version of the object they are making. ...
Well, one thing we try to do in Ruby is make (almost) perfect objects! )

I'm looking (for my own purposes) at the various Numeric classes,
and I think it's useful to consider them in terms of precision
potentially being lost on conversion and how we should cope with that.

(I'm using Microsoft Windows Vista (*1): if the behaviour shown doesn't work,
just increase n until it does! Admittedly this uses Integer not BigDecimal,
but it shows the potential problems if precision is lost.)

irb

n = 53
i = 2 ** n #=> 9007199254740992
ii = i + 1 #=> 9007199254740993
f = Float( i ) #=> 9.00719925474099e+015
ff = Float( ii ) #=> 9.00719925474099e+015
iii = Integer( ff ) #=> 9007199254740992
i == ii #=> false
i == f #=> true
ii == f #=> true
f == ff #=> true
i <=> ii #=> -1
i <=> f #=> 0
ii <=> f #=> 0

Colin Bartlett

(*1) Question: Why do you like Linux and BSD Unix so much?
You've never used either of them.
Answer: No, but I have used Microsoft Windows.
with apologies to Karl Kraus http://en.wikipedia.org/wiki/...

Adam Gardner

4/11/2009 9:28:00 PM

Roger Pack wrote:
> Thought I'd pass these thoughts by the readers here before sending them
> to core. They're my current wish list :)
>
> 1) add an Object#in? method to complement the existing Array#include?
>
> 2) add some useful lists of exceptions, ex: IO.SELECT_EXCEPTIONS,
> IO.READ_EXCEPTIONS, so that you can rescue the wide gamut of them
> appropriately, should you desire to.
>
> 3) provide an easier way to know which platform you're on than
> RUBY_PLATFORM =~ /mswin32|dgjpp|mingw/
>
> 4) (this one's controversial) remove the extra # for code in strings
> (i.e. "string#{code}") -> "string{code}" less typing.
>
> 5) add a BigDecimal(float) method.
> -> BigDecimal.new("%f" % float)
>
> 6) add Dir.directory?
> -> File.directory?
>
> Feedback?
> Thanks!
> -=r

Object#in? can be very useful in keeping code legible; it more likely to
be problematic in some circumstances than others. I'm using it in the
game I'm writing right now and it's working just fine, but I don't
really think it should be part of Ruby Core.

That said, it's very very easy to add yourself if you need it:

class Object
def in?(object)
if object.respond_to?(:include?) then
object.include? self
else
false
end
end #def in?
end #class Object
--
Posted via http://www.ruby-....

Joel VanderWerf

4/11/2009 11:19:00 PM

Roger Pack wrote:
>>> 4) (this one's controversial) remove the extra # for code in strings
>>> (i.e. "string#{code}") -> "string{code}" less typing.
>> Would not like having to escape { in strings...
>
> Ok. This next isn't meant as an attacking question but...do you use { in
> normal strings often? Granted probably more than #, but...?

Yes, quite extensively when generating C code. Would hate to have to use
\{...} instead of {...} for C blocks. Also, but less often, inside of

instance_eval "...",

or

eval "...", etc.

--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

Robert Klemme

4/12/2009 10:33:00 AM

On 11.04.2009 20:43, Roger Pack wrote:
>>> 1) add an Object#in? method to complement the existing Array#include?
>> -0
>>
>> I don't see the benefit but I'm also not strongly against. I do see
>> Joel's point about the reversion. Basically it is strange that every
>> object should be able to answer a question that only the collection can
>> answer. Plus, you can easily add it yourself if you need it.
>
> I kind of agree with Joel on this one, too.
>
> A few other observations:
>
> re: in?
> Currently with #select you've got one in Kernel [which is IO.select] but
> Arrays seem to have their own #select. So it is "conceivably possible"
> to have a "default #in?" and have it overridden by Clutch#in? or
> House#in? if desired.

That's not exactly an override situation because the "global" select is
used without an instance or with a class instance (IO) while
Enumerable#select is always used with an instance.

> Another option would be included? -- might be more ruby-y :)
>
>>> 2) add some useful lists of exceptions, ex: IO.SELECT_EXCEPTIONS,
>>> IO.READ_EXCEPTIONS, so that you can rescue the wide gamut of them
>>> appropriately, should you desire to.
>> A good idea. But I do not know how feasible this is. Not all OS have
>> the same error reporting mechanisms and the mapping from OS errors to
>> exception types would have to be maintained of all platforms.
>
> True, mapping exceptions directly from OS to OS would be problematic.
> And knowing which ones are on each OS is also annoying.
> I am proposing more of a (platform dependent) container of all possible
> exceptions, regardless of what they may mean. Or have them all include
> a common ancestor--same result.

There is SystemCallError already:

ObjectSpace.each_object(Class) do |cl|
p cl if cl.ancestors.include? SystemCallError
end

>>> 3) provide an easier way to know which platform you're on than
>>> RUBY_PLATFORM =~ /mswin32|dgjpp|mingw/
>> -1
>>
>> This would make a Ruby specific unification of operating systems
>> necessary. This means that not only maintainers of automake need to
>> keep track of operating systems but also maintainers of Ruby. Other
>> difficulties are: how much level of detail do you provide? For one
>> application it may be enough to know it's running on Linux, the other
>> one needs to know the kernel version and a third one does not bother
>> about versions but must know the distro. I see too much effort for too
>> little benefit.
>
> True maintaining this is annoying, but I'd also propose that it's
> useful. Currently in 1.9 we have:
>>> RUBY_VERSION
> => "1.9.2"
>>> RUBY_PLATFORM
> => "x86_64-linux"
>>> RUBY_ENGINE
> => "ruby"
>
> Typically "enough" OS information is given in RUBY_PLATFORM to determine
> the platform--it's just "hard" to use that for such. My example being
> that knowing if you're on windows is something like RUBY_PLATFORM =~
> /dgjpp|mingw|mswin/
> which seems overly complex for me. And very hard to get right the first
> time (ex: RUBY_PLATFORM =~ /win/ doesn't work--that includes darwin).

And how do you want to resolve the issues I have raised in my posting?
The question really is "what is a platform"? When using cygwin, are you
"on Windows" or not? etc.

>>> 5) add a BigDecimal(float) method.
>>> -> BigDecimal.new("%f" % float)
>> 0
>>
>> Seems reasonable at first sight but the absence might have a reason.
>> For example, by making the conversion to String explicit it is more
>> obvious that float and BigDecimal are not really compatible.
>
> Yeah I wonder that myself. I was just hoping to make it easier to use
> BigDecimal, since Floats are so imprecise to use for decimal numbers :)

Which is exactly the reason why conversion to a BigDecimal should not be
too easy. String with decimal encoded number as input format for a
BigDecimal is really the proper type as you can see from the name
"BigDecimal". :-)

>> if test ?d, "some dir"
>
> Could you explain that again? Not sure I do understand the idiom.
> Looks like bash?

[robert@ora01 ~]$ ruby19 -e 'puts "yeah!" if test ?d, "."'
yeah!
[robert@ora01 ~]$

Happy Easter!

robert

comp.lang.ruby

a few thoughts for ruby...

Roger Pack

Joel VanderWerf

Roger Pack

Nobuyoshi Nakada

Robert Klemme

Nobuyoshi Nakada

Roger Pack

Colin Bartlett

Adam Gardner

Joel VanderWerf

Robert Klemme

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