Hi Mark,
Glad you enjoyed Pine. A couple more details, because you seem interested:
A Proc isn't quite just a function (I don't think a mere function really
exists in Ruby) -- it's a closure, which means variables from a lexical
scope are bound into it and available in it. For example:
f = begin
a = 0
proc { a += 1 }
end
f.call #=> 1
f.call #=> 2
Blocks also aren't objects but, like methods, they can be:
def g
block_given? ? yield : :no_block
end
g { puts "this block never gets to be an object" }
method_object = method(:g)
g(&method_object) #=> :no_block
That last example shows how you can use a Method object or Proc (or any
object with a to_proc method) as a block with the ampersand operator.
If you followed this, Ruby Quiz might interest you for further exercises.
(There is a book made from the early ones. There were a few iterations.
You'll find archived websites in the Internet Archive and [QUIZ] messages
in the ruby-talk mailing list archive.)
Cheers,
Dave
On Sat, Aug 2, 2014 at 2:49 PM, Marky Mark <[email protected]> wrote:
> Thanks, Chris Pine's explanation is nice and clear, and very
> comprehensible to my C++ mind. A proc is just (!) a function-as-object. And
> a block is just an anonymous proc. Though I'm sure I'm missing some Ruby
> subtleties there. I had overlooked the fact that methods aren't objects and
> hence aren't first-class entities. Hey, I thought *everything* was an
> object in Ruby :-)
>
> His profiling example is something I'm sure I've done in C++ too. Handing
> in functions (ok, function pointers) as things-to-do is pretty standard.
> Though you have to take more care about matching your prototypes just to
> get it past the compiler.
>
> I'm amused by his comment in passing about how nobody ever actually does
> any currying.
>
>
> On Friday, August 1, 2014 10:09:29 PM UTC+10, Dave Burt wrote:
>
>> Hi Mark,
>>
>> First a minor correction: "case a when b ..." is actually "if b === a
>> ..." -- the === method is called on object b with argument a.
>>
>> "yields" is not a clear word to use -- in Ruby it refers to a method
>> calling a passed block.
>>
>> But you're right, you have misunderstood what proc returns. The proc
>> method returns a Proc object, and "Proc objects are blocks of code." The
>> Proc object in your example accepts an argument, calls its "more_blue?"
>> method, and returns the result. That result will be true or false, but the
>> Proc is a essentially function which can be called.
>>
>> Then, also, the Proc has a === method. case...when turns into if like
>> this:
>>
>> if (proc { |color| color.more_blue? }) === color
>> "blueish"
>>
>> Proc#=== returns the result of the Proc when called with the case
>> subject. So to run that when clause, the proc will be called with the color
>> as argument, equivalent to this if statement:
>>
>> if (proc { |color| color.more_blue? }).call(color)
>> "blueish"
>>
>> http://www.ruby-doc.org/core-2.1.1/Kernel.html#method-i-proc
>> http://www.ruby-doc.org/core-2.1.1/Proc.html.
>>
>> Chris Pine wrote a great intro to blocks and procs in Ruby over a decade
>> ago now, which includes some exercises to play with and cement your
>> understanding:
>> https://pine.fm/LearnToProgram/?Chapter=10
>>
>> Cheers,
>> Dave
>>
>>
>> On Fri, Aug 1, 2014 at 6:01 PM, Marky Mark <[email protected]> wrote:
>>
>>> Um, I just wrote my original question out and stared at it some more and
>>> realised it was a stupid question to begin with :-(
>>>
>>> But the more I think about it the more I'm confused (and maybe this is
>>> where hearing what Tim said at the time would help).
>>>
>>> Conceptually I see "case a when b ... when c ... else ..." as being the
>>> same as "if a === b ... elsif a === c ... else ..." (as indeed slides 67-69
>>> show) but that seems to fail for slide 62's use of proc:
>>>
>>> case color
>>> when proc { |color| color.more_blue? }
>>> "blueish"
>>>
>>> because comparing color with what the proc yields (true or false) surely
>>> doesn't work. Am I misunderstanding what proc yields?
>>>
>>>
>>> On Friday, August 1, 2014 5:08:06 PM UTC+10, Dave Burt wrote:
>>>
>>>> Thanks for the notes, Tim!
>>>>
>>>> Mark, post your case questions here!
>>>>
>>>> On the same topic, here is an article by Why on another feature of
>>>> Ruby's case statements: you can *splat* an array like this:
>>>>
>>>> foo = 3
>>>> ARRAY = [/abc/, Hash, 1..5]
>>>> case foo; when *ARRAY; 'included'; else "doesn't === anything in the
>>>> array"; end
>>>>
>>>> http://viewsourcecode.org/why/redhanded/bits/wonderOfTheWhenBeFlat.html
>>>>
>>>> Cheers,
>>>> Dave
>>>>
>>>>
>>>> On Fri, Aug 1, 2014 at 2:53 PM, Marky Mark <[email protected]> wrote:
>>>>
>>>>> Just slides though, no soundtrack? Familiar with case statements as I
>>>>> am in general, I can't help thinking I'm missing a little of the
>>>>> subtlety/reasoning w.r.t Ruby. I do have one or two stupid questions.
>>>>> Should I post here or ask you privately?
>>>>>
>>>>>
>>>>> On Thursday, July 31, 2014 3:04:32 PM UTC+10, Tim Moore wrote:
>>>>>>
>>>>>> Yes, I'll echo Dave's thoughts: thanks to the organisers and the
>>>>>> substitute host!
>>>>>>
>>>>>> My slides are up at https://speakerdeck.com/tim
>>>>>> moore/rubys-magical-case-statement and http://www.slideshare.net/
>>>>>> timothymoore/rubys-magical-case-statement (take your pick)
>>>>>>
>>>>>> On Thursday, July 31, 2014 8:52:42 AM UTC+10, Dave Burt wrote:
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Thanks to the organisers and speakers for another great evening.
>>>>>>>
>>>>>>> May I ask again for links to any of the talks that are available?
>>>>>>>
>>>>>>> I think Duncan referenced his Github repo https://github.com/duncan
>>>>>>> -bayne/presentations
>>>>>>>
>>>>>>> Cheers,
>>>>>>> Dave
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Jul 25, 2014 at 1:17 PM, Mario Visic <[email protected]>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hi All
>>>>>>>>
>>>>>>>> The Melbourne Ruby meet will be happening next wednesday evening
>>>>>>>> (the 30th July), with our usual array of entertaining talks, delicious
>>>>>>>> food, tasty beverages, and delightful company (that’s you!).
>>>>>>>>
>>>>>>>> WHEN: Wednesday 30th July, arrive at 6pm for a 6:30pm start,
>>>>>>>> wrapping up around 9pm.
>>>>>>>> WHERE: Inspire9, Level 1, 41-43 Stewart Street
>>>>>>>> WHAT: Three speakers, plus socialising, good food (not pizza) and
>>>>>>>> drinks.
>>>>>>>>
>>>>>>>> Our line-up this month is:
>>>>>>>> Jordan Lewis + Luke Arndt - Styleguide driven development
>>>>>>>> Duncan Bayne - There’s no such thing as magic - tools and
>>>>>>>> techniques for Ruby developers
>>>>>>>> Tim Moore - Case Statements and ===
>>>>>>>>
>>>>>>>> All of these details are repeated on Meetup, for those who prefer
>>>>>>>> that as their source of event information:
>>>>>>>> http://www.meetup.com/Ruby-On-Rails-Oceania-Melbourne/events
>>>>>>>> /175705562/
>>>>>>>>
>>>>>>>> Yet again, food is sponsored by Envato, Lookahead Search and
>>>>>>>> Redbubble, the drinks by Zendesk, and the space by Inspire9.
>>>>>>>>
>>>>>>>> If you've any questions or thoughts, get in touch - we're looking
>>>>>>>> forward to seeing you all there :)
>>>>>>>>
>>>>>>>> --
>>>>>>>> Mario & Pat
>>>>>>>>
>>>>>>>> --
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>>>>>>>> Visit this group at http://groups.google.com/group/rails-oceania.
>>>>>>>> For more options, visit https://groups.google.com/d/optout.
>>>>>>>>
>>>>>>>
>>>>>>> --
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>>>>>
>>>>
>>>>
>>
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