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Re: How can I generate new variables?

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Kyle X. wrote in post #990113:
> First off thank you for the reply, and as you can probably tell I am
> very novice at ruby >

No problem--that's what this forum is for.

>>
>> require 'enumerator'  #not necessary in ruby 1.9
>>
>> master_arr = []
>> data = [1, 2, 3,  4, 5, 6,  7, 8]
>>
>> data.each_slice(3) do |triplet|
>>   master_arr << triplet
>> end
>>
>> p master_arr
>>
>> --output:--
>> [[1, 2, 3], [4, 5, 6], [7, 8]]
>
> I am writing this for SketchUP so I am using Ruby 1.8.6 and am having an
> issue with require 'enumerator', as it does not exist in their library
> as far as I can tell
>

I'm using ruby 1.8.6 too, and the Enumerator module is part of the ruby 
standard library.  Are you sure you spelled it right?  But if it's not 
provided, it's not provided.


> I was wondering if you could help me understand this command better as
> well.  "data.each_slice(3) do |triplet|"  The "(3)" here means slice
> after 3 entries in data correct?

Yes, the each_slice() method allows you to chop up an array into chunks 
of the specified size.

> The word triplet used, is this word
> required or could it be any word as long as it is consistent below i.e.
> :  do |x| master_arr << x?  Sorry for the basic question, but I just
> want to clarify.
>

'triplet' is just a descriptive variable name.  It is a "block 
parameter" which is just like a method parameter:

def do_stuff(x)  #x is a method parameter
  x+2  #or you can explicitly write: return x+2
end

answer = do_stuff(5)
puts answer   #=> 7


Ruby uses blocks everywhere.  Here is a simple example:

words = ["hello", "world", "goodbye"]

words.each do |word|
  puts word
end

--output:--
hello
world
goodbye

The each() method sends each element of the array to the block, which is 
this part:

      do |word|
  puts word
end

'do' signals the start of a block.  What happens is that ruby calls the 
block,  which is like a method with, for each element of the array.  In 
my example, the element of the array is assigned to the variable named 
'word', and then inside the block you can do whatever you want to the 
word variable.

The map() function, like each(), tells ruby to send each element of the 
array to the block.  However, map() also *takes the return value of the 
block* and shoves it into a new array:


words = ["hello", "world", "goodbye"]

new_arr = words.map do |x|
  1
end

p new_arr

--output:--
[1, 1, 1]

In that example, the block returns 1 for every element of the array. 
But you can use map to do more useful things--like capitalize all the 
words in the array:

words = ["hello", "world", "goodbye"]

new_arr = words.map do |x|
  x.capitalize  #same as: 'return x.capitalize'
end

p new_arr

--output:--
["Hello", "World", "Goodbye"]

So whenever, you want to do something to every member of an array, map() 
is a good choice.

-- 
Posted via http://www.ruby-forum.com/.

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Thread

How can I generate new variables? "Kyle X." <haebooty@yahoo.com> - 2011-03-30 19:42 -0500
  Re: How can I generate new variables? 7stud -- <bbxx789_05ss@yahoo.com> - 2011-03-30 20:14 -0500
    Re: How can I generate new variables? "Kyle X." <haebooty@yahoo.com> - 2011-03-30 22:08 -0500
      Re: How can I generate new variables? Gunther Diemant <g.diemant@gmx.net> - 2011-03-31 03:08 -0500
        Re: How can I generate new variables? "Kyle X." <haebooty@yahoo.com> - 2011-03-31 14:30 -0500
      Re: How can I generate new variables? Robert Klemme <shortcutter@googlemail.com> - 2011-03-31 03:11 -0500
      Re: How can I generate new variables? 7stud -- <bbxx789_05ss@yahoo.com> - 2011-03-31 20:06 -0500
  Re: How can I generate new variables? "Kyle X." <haebooty@yahoo.com> - 2011-04-02 01:18 -0500
    Re: How can I generate new variables? Robert Klemme <shortcutter@googlemail.com> - 2011-04-04 02:15 -0500

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