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comp.lang.ruby

#returning and #tap

Trans

11/8/2006 2:31:00 PM

Had use for this today: #returning is a convenience method you'll find
in both Facets and ActiveSupport. Jamis' blogged it the other day:


http://weblog.jamisbuck.org/2006/10/27/mining-activesupport-object...

Any one else think this is worthy of standard Ruby?

Also, a cool twist on the same concept is #tap. Check out the
MenTaLgeniuS:


http://moonbase.rydia.net/mental/blog/programming/eavesdropping-on-expres...

T.
65 Answers

James Gray

11/8/2006 2:54:00 PM

0

On Nov 8, 2006, at 8:40 AM, Trans wrote:

> Had use for this today: #returning is a convenience method you'll find
> in both Facets and ActiveSupport. Jamis' blogged it the other day:
>
>
> http://weblog.jamisbuck.org/2006/10/27/mining-activesuppo...
> returning
>
> Any one else think this is worthy of standard Ruby?
>
> Also, a cool twist on the same concept is #tap. Check out the
> MenTaLgeniuS:
>
>
> http://moonbase.rydia.net/mental/blog/programming/eavesdr...
> expressions.html

One of the comments to the original article combines both methods
into a with() method that seems to be the best of both worlds.

James Edward Gray II

Kalman Noel

11/8/2006 3:02:00 PM

0

Trans wrote:
[about #returning and #tap]

See also the »with construction« thread, especially as of:

45426320.9070405@path.berkeley.edu

Kalman

Luke Graham

11/8/2006 4:02:00 PM

0

MenTaLguY's use cases seem the more convincing of the two. Why would I
care about keeping an object anonymous when I'm leaving that scope
anyway? I guess in an inline lambda function it might be appropriate.
'tap' is what it's likely to be used for most of the time. I'd call it
'k', personally, maybe with an alias to 'tap' or 'tee'. I would like
to see it in standard Ruby.

On 11/8/06, Trans <transfire@gmail.com> wrote:
> Had use for this today: #returning is a convenience method you'll find
> in both Facets and ActiveSupport. Jamis' blogged it the other day:
>
>
> http://weblog.jamisbuck.org/2006/10/27/mining-activesupport-object...
>
> Any one else think this is worthy of standard Ruby?
>
> Also, a cool twist on the same concept is #tap. Check out the
> MenTaLgeniuS:
>
>
> http://moonbase.rydia.net/mental/blog/programming/eavesdropping-on-expres...
>
> T.
>
>
>

Trans

11/8/2006 4:03:00 PM

0


James Edward Gray II wrote:
> On Nov 8, 2006, at 8:40 AM, Trans wrote:
>
> > Had use for this today: #returning is a convenience method you'll find
> > in both Facets and ActiveSupport. Jamis' blogged it the other day:
> >
> >
> > http://weblog.jamisbuck.org/2006/10/27/mining-activesuppo...
> > returning
> >
> > Any one else think this is worthy of standard Ruby?
> >
> > Also, a cool twist on the same concept is #tap. Check out the
> > MenTaLgeniuS:
> >
> >
> > http://moonbase.rydia.net/mental/blog/programming/eavesdr...
> > expressions.html
>
> One of the comments to the original article combines both methods
> into a with() method that seems to be the best of both worlds.

Oh yea! I remember #with from way back, but then I don't recall anyone
suggesting it return the object. Cool.

One thing though, while it covers #tap just fine, it doesn't read the
same as #returning.

T.

Luke Graham

11/8/2006 4:24:00 PM

0

Just realised that of course tap != k :P


On 11/8/06, Trans <transfire@gmail.com> wrote:
>
> James Edward Gray II wrote:
> > On Nov 8, 2006, at 8:40 AM, Trans wrote:
> >
> > > Had use for this today: #returning is a convenience method you'll find
> > > in both Facets and ActiveSupport. Jamis' blogged it the other day:
> > >
> > >
> > > http://weblog.jamisbuck.org/2006/10/27/mining-activesuppo...
> > > returning
> > >
> > > Any one else think this is worthy of standard Ruby?
> > >
> > > Also, a cool twist on the same concept is #tap. Check out the
> > > MenTaLgeniuS:
> > >
> > >
> > > http://moonbase.rydia.net/mental/blog/programming/eavesdr...
> > > expressions.html
> >
> > One of the comments to the original article combines both methods
> > into a with() method that seems to be the best of both worlds.
>
> Oh yea! I remember #with from way back, but then I don't recall anyone
> suggesting it return the object. Cool.
>
> One thing though, while it covers #tap just fine, it doesn't read the
> same as #returning.
>
> T.
>
>
>

Eric Hodel

11/15/2006 9:50:00 PM

0

On Nov 8, 2006, at 6:40 AM, Trans wrote:

> Had use for this today: #returning is a convenience method you'll find
> in both Facets and ActiveSupport. Jamis' blogged it the other day:
>
> http://weblog.jamisbuck.org/2006/10/27/mining-activesuppo...
> returning
>
> Any one else think this is worthy of standard Ruby?

From the blog post:

>> The latter is no shorter than the former, but it reads more
>> elegantly. It feels more “Rubyish”. And there are times that it
>> can save you a few lines of code, if that’s important. (Just scan
>> the Rails source code for more examples.)

So... it usually doesn't save any lines, it adds typing, it hides the
object you're returning in the middle of a statement and it is
significantly more expensive to execute[1]. (Oh, but maybe, in some
cases, it might save you one or two lines of code.)

No thanks.

I don't think that makes it more rubyish. Every time I've
encountered #returning in Rails I've found it decreased the
readability of the code and uselessly increased the complexity.
(Wait, now what does this return? oh, yeah, way up there.)

1:

Rehearsal ---------------------------------------------
empty 0.290000 0.000000 0.290000 ( 0.391447)
returning 5.120000 0.050000 5.170000 ( 5.467861)
regular 2.660000 0.020000 2.680000 ( 2.900946)
------------------------------------ total: 8.140000sec

user system total real
empty 0.300000 0.000000 0.300000 ( 0.316623)
returning 5.160000 0.050000 5.210000 ( 5.815804)
regular 2.650000 0.020000 2.670000 ( 2.824744)

require 'benchmark'

def returning(value)
yield(value)
value
end

N = 1_000_000

Benchmark.bmbm do |bm|
bm.report 'empty' do
N.times do end
end

bm.report 'returning' do
N.times do returning(Object.new) do |o| o.nil? end end
end

bm.report 'regular' do
N.times do o = Object.new; o.nil?; o end
end

end

--
Eric Hodel - drbrain@segment7.net - http://blog.se...
This implementation is HODEL-HASH-9600 compliant

http://trackmap.rob...

Trans

11/15/2006 10:50:00 PM

0


Eric Hodel wrote:
> On Nov 8, 2006, at 6:40 AM, Trans wrote:
>
> > Had use for this today: #returning is a convenience method you'll find
> > in both Facets and ActiveSupport. Jamis' blogged it the other day:
> >
> > http://weblog.jamisbuck.org/2006/10/27/mining-activesuppo...
> > returning
> >
> > Any one else think this is worthy of standard Ruby?
>
> From the blog post:
>
> >> The latter is no shorter than the former, but it reads more
> >> elegantly. It feels more "Rubyish". And there are times that it
> >> can save you a few lines of code, if that's important. (Just scan
> >> the Rails source code for more examples.)
>
> So... it usually doesn't save any lines, it adds typing, it hides the
> object you're returning in the middle of a statement and it is
> significantly more expensive to execute[1]. (Oh, but maybe, in some
> cases, it might save you one or two lines of code.)

Er... that seems a backwards and inconsitant interpretation. How can it
add typing if can save a line or two of code? Moreover it is optional
usage, so use it when it saves you the lines and not otherwise, or if
it simply adds to the readility, and not otherwise. As for "hides the
object you're returning in the middle of a statement", how's that? The
object is stated at the very beginning. It's very readible. It says:
here is the object we will return after doing the following things to
it. Without it you have no idea what the goal is --return statements
could be deeping embedded inside the rest of the code.

Now, I grant you the speed issue sucks --and if that's important, again
you have the option of not using it. But also, if it were built in
perhaps it could be optimized (?)

> No thanks.
>
> I don't think that makes it more rubyish. Every time I've
> encountered #returning in Rails I've found it decreased the
> readability of the code and uselessly increased the complexity.
> (Wait, now what does this return? oh, yeah, way up there.)

Well, a def can easily get "mucky". #returning can help provide some
structural constraint. Most the time it isn't needed, but on occasion I
find it helps.

Besides that the 'tap' functionality can be very hepful in it's own
right.

T.

Eric Hodel

11/15/2006 11:33:00 PM

0

On Nov 15, 2006, at 2:50 PM, Trans wrote:
> Eric Hodel wrote:
>> On Nov 8, 2006, at 6:40 AM, Trans wrote:
>>> Had use for this today: #returning is a convenience method you'll
>>> find
>>> in both Facets and ActiveSupport. Jamis' blogged it the other day:
>>>
>>> http://weblog.jamisbuck.org/2006/10/27/mining-activesuppo...
>>> returning
>>>
>>> Any one else think this is worthy of standard Ruby?
>>
>> From the blog post:
>>
>>>> The latter is no shorter than the former, but it reads more
>>>> elegantly. It feels more "Rubyish". And there are times that it
>>>> can save you a few lines of code, if that's important. (Just scan
>>>> the Rails source code for more examples.)
>>
>> So... it usually doesn't save any lines, it adds typing, it hides the
>> object you're returning in the middle of a statement and it is
>> significantly more expensive to execute[1]. (Oh, but maybe, in some
>> cases, it might save you one or two lines of code.)
>
> Er... that seems a backwards and inconsitant interpretation. How
> can it
> add typing if can save a line or two of code?

Most of the time it adds code. Look at the two examples on the blog
post. In the returning case I add "returning do || end" in the
simple case I have an extra "=".

The example shows in the blog post shows returning saving exactly 0
lines of code. It claims that in some cases it saves lines, but
doesn't give any examples, so it is probably a very rare statement.

> Moreover it is optional usage, so use it when it saves you the
> lines and not otherwise, or if it simply adds to the readility, and
> not otherwise.

If it commonly saved lines then I'd expect the blog post would have
used such an example. I doubt that it commonly saves lines (the blog
post implies it usually does nothing to the line count).

> As for "hides the object you're returning in the middle of a
> statement", how's that? The object is stated at the very beginning.

In most every other place in ruby the last line of a code grouping
construct is the return value. This is the way I've been reading my
Ruby for years. With #returning the return value is buried in the
middle of the line between "returning" and "do".

> It's very readible. It says: here is the object we will return
> after doing the following things to it.

That's extra state I have to keep in my brain to keep the code straight.

Traditional code doesn't require me to hold extra state in my head
because its linear. Linear is simpler and simpler is more readable.

> Without it you have no idea what the goal is --return statements
> could be deeping embedded inside the rest of the code.

This statement is orthogonal to the use of #returning. You may throw
in extra returns anywhere you like regardless of the #returning block.

> Now, I grant you the speed issue sucks --and if that's important,
> again
> you have the option of not using it. But also, if it were built in
> perhaps it could be optimized (?)

Its simpler to just not have it at all. #returning gives no great
benefit and has many downsides.

>> No thanks.
>>
>> I don't think that makes it more rubyish. Every time I've
>> encountered #returning in Rails I've found it decreased the
>> readability of the code and uselessly increased the complexity.
>> (Wait, now what does this return? oh, yeah, way up there.)
>
> Well, a def can easily get "mucky". #returning can help provide some
> structural constraint. Most the time it isn't needed, but on
> occasion I
> find it helps.

#returning isn't going to add any structure since it doesn't really
do anything. You're really just replacing 'var' with 'end' and
adding a bunch of whitespace.

> Besides that the 'tap' functionality can be very hepful in it's own
> right.

So what? I didn't mention #tap in my email.

--
Eric Hodel - drbrain@segment7.net - http://blog.se...
This implementation is HODEL-HASH-9600 compliant

http://trackmap.rob...

Joel VanderWerf

11/16/2006 1:41:00 AM

0

Eric Hodel wrote:
...
> So... it usually doesn't save any lines, it adds typing, it hides the
> object you're returning in the middle of a statement and it is
> significantly more expensive to execute[1]. (Oh, but maybe, in some
> cases, it might save you one or two lines of code.)
>
> No thanks.
>
> I don't think that makes it more rubyish. Every time I've encountered
> #returning in Rails I've found it decreased the readability of the code
> and uselessly increased the complexity. (Wait, now what does this
> return? oh, yeah, way up there.)

This variant saves typing and IMO is more idiomatically ruby:

class Object
def then
yield(self)
self
end
end

def foo
@foo ||= Foo.new.then do |f|
f.bar = "bar"
end
end


Otherwise you have to do this:

def foo
unless @foo
@foo = Foo.new
@foo.bar = "bar"
end
@foo
end

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

Joel VanderWerf

11/16/2006 1:45:00 AM

0

Joel VanderWerf wrote:
> This variant saves typing and IMO is more idiomatically ruby:
>
> class Object
> def then
> yield(self)
> self
> end
> end

Oops, sorry. I didn't realize that #tap is the same as #then.

I can't quite see why "tap" is a good name for that, though...

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