Question - looking for library to use for query like code?

ruby-talk
1

Can this be done with Ruby? (this may be a shot in the dark)

Say you have a text file with a lot of data and you want to group all of
your data by a specific value. Is there a way to code something in ruby
similar to a query that you would create using sql. Can this even be
done using Ruby? And if so, is there a library that you can refer me to?
If not, do you know any alternative ways? Thanks, MC

example of text:

auto, model
car, honda
truck, chevy
car, nissan
truck, toyota
truck, ford

how i'd like it to look:

car, honda, nissan,
truck, chevy, toyota, ford

···

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

2

Quoting Mmcolli00 Mom <mmc_collins@yahoo.com>:

Can this be done with Ruby? (this may be a shot in the dark)

Say you have a text file with a lot of data and you want to group all of
your data by a specific value. Is there a way to code something in ruby
similar to a query that you would create using sql. Can this even be
done using Ruby? And if so, is there a library that you can refer me to?
If not, do you know any alternative ways? Thanks, MC

example of text:

auto, model
car, honda
truck, chevy
car, nissan
truck, toyota
truck, ford

how i'd like it to look:

car, honda, nissan,
truck, chevy, toyota, ford
--
Posted via http://www.ruby-forum.com/\.

Of course this is possible, and rather easy to write. Here are bits I would use:

cars = hash.new

file = File.open("textfile.txt")
file.each {
  > line |
  wordarray = line.split(/,\s*/)

  cars[wordarray[0]] << wordarray[1]
}
file.close

file = File.open("outfile.txt", "w")
file << "cars, "
cars["cars"].each { |car| file << car << ", " }
file << "\n"
cars.["truck"].each { |car| file << car << ", " }
file << "\n"
file.close

This is not a complete, nor a general solution, but this should give you an
idea.

Jean-Denis

3

Can this be done with Ruby? (this may be a shot in the dark)

Anything can be done with Ruby. :wink:

Say you have a text file with a lot of data and you want to group all of
your data by a specific value. Is there a way to code something in ruby
similar to a query that you would create using sql. Can this even be
done using Ruby? And if so, is there a library that you can refer me to?
If not, do you know any alternative ways? Thanks, MC

I'll show some pure Ruby code below that seems to do what you want, but if you really want a query language you have several options. Personally, I would use the Amalgalite gem to get SQLite. You would then just read the data and write it into a database. You can then query it in anyway you like.

example of text:

auto, model
car, honda
truck, chevy
car, nissan
truck, toyota
truck, ford

how i'd like it to look:

car, honda, nissan,
truck, chevy, toyota, ford

Here's some code that does that:

#!/usr/bin/env ruby -wKU

headers = DATA.gets.strip.split(/,\s*/)

related = { }
DATA.each do |row|
   fields = Hash[*headers.zip(row.strip.split(/,\s*/)).flatten]
   (related[fields["auto"]] ||= ) << fields["model"]
end

related.keys.sort.each do |key|
   puts(([key] + related[key]).join(", "))
end

__END__
auto, model
car, honda
truck, chevy
car, nissan
truck, toyota
truck, ford

Hope it helps.

James Edward Gray II

···

On Feb 6, 2009, at 8:32 AM, Mmcolli00 Mom wrote:

4

data = Hash.new {|h,k| h[k] = }

IO.foreach("myfile.txt"){|line|
  type, make = line.strip.split( / *, */ )
  data[ type ] << make
}

p data

···

On Feb 6, 8:32 am, Mmcolli00 Mom <mmc_coll...@yahoo.com> wrote:

Can this be done with Ruby? (this may be a shot in the dark)

Say you have a text file with a lot of data and you want to group all of
your data by a specific value. Is there a way to code something in ruby
similar to a query that you would create using sql. Can this even be
done using Ruby? And if so, is there a library that you can refer me to?
If not, do you know any alternative ways? Thanks, MC

example of text:

auto, model
car, honda
truck, chevy
car, nissan
truck, toyota
truck, ford

how i'd like it to look:

car, honda, nissan,
truck, chevy, toyota, ford
--
Posted viahttp://www.ruby-forum.com/.

5

James' solution to the previous question being so much better than mine (which I
did for my learning purposes), I dare asking about how to iterate over two
arrays in parallel. I don't see a way to use the iteration methods, and my
solution below doesn't feel idiomatic at all:

array1 = [1, 2, 3]
array2 = ["one", "two", "three"]
# note: both arrays are known to be the same size

(0..array1.size-1).each {
  > i |
  print "#{array2[i]} = #{array1[i]}\n"
}

6

Use the block form of zip:

array1.zip(array2) {|i,j| print "#{i} = #{j}\n"}

martin

···

On Fri, Feb 6, 2009 at 8:54 PM, Jean-Denis Muys <jdmuys@kleegroup.com> wrote:

James' solution to the previous question being so much better than mine (which I
did for my learning purposes), I dare asking about how to iterate over two
arrays in parallel. I don't see a way to use the iteration methods, and my
solution below doesn't feel idiomatic at all:

array1 = [1, 2, 3]
array2 = ["one", "two", "three"]
# note: both arrays are known to be the same size

7

James' solution to the previous question being so much better than mine (which I did for my learning purposes),

I think your solution was just fine.

I dare asking about how to iterate over two arrays in parallel. I don't see a way to use the iteration methods, and my solution below doesn't feel idiomatic at all:

array1 = [1, 2, 3]
array2 = ["one", "two", "three"]
# note: both arrays are known to be the same size

(0..array1.size-1).each {
> i |
print "#{array2[i]} = #{array1[i]}\n"
}

Here's one way:

>> array1 = (1..3).to_a
=> [1, 2, 3]
>> array2 = %w[one two three]
=> ["one", "two", "three"]
>> array1.zip(array2) { |num, word| puts "#{num} #{word}" }
1 one
2 two
3 three
=> nil

and another:

>> require "generator"
=> true
>> SyncEnumerator.new(array1, array2).each { |num, word| puts "#{num} #{word}" }
1 one
2 two
3 three
=> #<SyncEnumerator:0x1115e58 @gens=[#<Generator:0x1115de0 @cont_endp=#<Continuation:0x11154bc>, cont_yieldnil, queue, block#<Proc:0x0111e15c@/usr/local/lib/ruby/1.8/generator.rb:71>, cont_next#<Continuation:0x1115624, @index=3>, #<Generator:0x1115cc8 @cont_endp=#<Continuation:0x111546c>, cont_yieldnil, queue, block#<Proc:0x0111e15c@/usr/local/lib/ruby/1.8/generator.rb:71>, cont_next#<Continuation:0x1115570, @index=3>]

Hope that helps.

James Edward Gray II

···

On Feb 6, 2009, at 9:24 AM, Jean-Denis Muys wrote:

8

Hope that helps.

Yes indeed, quite a lot. Thanks to both of you.