a better way to do this job?

[Zhenning Guan]

topics.each do |f|
times +=1
puts f.title
if times > 4
break


a little ugly, doesn't it?

 

[Stefano Crocco]

Alle Tuesday 10 February 2009, Zhenning Guan ha scritto:

topics.each do |f|
times +=1
puts f.title
if times > 4
break


a little ugly, doesn't it?

If topics is an array, you can use:

topics[0..4].each{|f| puts f.title}

Another option, which can be used for any Enumerable object is:

topics.each_with_index do |f, i|
puts f.title
break if i > 4
end

While not as nice as the first version, it's a bit clearer than your code.

I hope this helps

Stefano

 

[Jesús Gabriel y Galán]

topics.each do |f|
times +=1
puts f.title
if times > 4
break


a little ugly, doesn't it?

topics[0,5].each do |f|
puts f.title
end

# if you need the variable "times" to have the same value as above:
# times = topics[0,5].size

Jesus.

 

[Ryan Davis]

topics.each do |f|
times +=1
puts f.title
if times > 4
break

there are a lot of ways. My first reaction is:

topics.first(5).each do |f|
puts f.title
end

If you define to_s on the topic class to return title then you can do:

puts topics.first(5)

and be done with it.

 

[7stud --]

topics.each do |f|
times +=1
puts f.title
if times > 4
break

In my opinion, it's nicer than the first version because it doesn't have
to create a sub array in memory, like all the solutions posted so far
do, which could be a problem with large arrays and large slices.

4.times do |i|
puts topics.title
end

 

[Julian Leviston]

Your code also won't work. Your tempvar is not declared and you have
no end to the block.

topics[0..3].each do |topic|
puts topic
end

Blog: http://random8.zenunit.com/
Learn rails: http://sensei.zenunit.com/

 

[Julian Leviston]

First doesn't take an argument I'm ruby. It does
If you're using rails enumerable mixin

Blog: http://random8.zenunit.com/
Learn rails: http://sensei.zenunit.com/

 

[Julian Leviston]

Slices and 'sub-arrays' aren't copies of the objects, they simply
refer to the identical objects.

Blog: http://random8.zenunit.com/
Learn rails: http://sensei.zenunit.com/

topics.each do |f|
times +=1
puts f.title
if times > 4
break

In my opinion, it's nicer than the first version because it doesn't
have
to create a sub array in memory, like all the solutions posted so far
do, which could be a problem with large arrays and large slices.

4.times do |i|
puts topics.title
end

 

[David A. Black]

Hi --

First doesn't take an argument I'm ruby. It does
If you're using rails enumerable mixin

$ ruby19 -ve 'puts [1,2,3,4].first(2)'
ruby 1.9.1p0 (2009-01-30 revision 21907) [i686-linux]
1
2


David

--
David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Coming in 2009: The Well-Grounded Rubyist (http://manning.com/black2)

http://www.wishsight.com => Independent, social wishlist management!

 

[David A. Black]

Hi --

Slices and 'sub-arrays' aren't copies of the objects, they simply refer to
the identical objects.

The same can be said of any array; the objects inside it exist (in
many cases, at least) already. Still, container objects do take up
memory. If you don't believe it, try this:

ruby -e 'a = [:a,:b,:c]; b = []; while true; b << a[0,3]; end'


David

--
David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Coming in 2009: The Well-Grounded Rubyist (http://manning.com/black2)

http://www.wishsight.com => Independent, social wishlist management!

 

[David A. Black]

Hi --

In my opinion, it's nicer than the first version because it doesn't have
to create a sub array in memory, like all the solutions posted so far
do, which could be a problem with large arrays and large slices.

Ryan had something like:

topics.first(5).each do |t|
puts t.title
end

which, I believe, does not create an intermediate array because
topics.first(5) returns an enumerator.


David

--
David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Coming in 2009: The Well-Grounded Rubyist (http://manning.com/black2)

http://www.wishsight.com => Independent, social wishlist management!

 

[Tom Link]

=A0 =A0ruby -e 'a =3D [:a,:b,:c]; b =3D []; while true; b << a[0,3]; end'

That's a little bit unfair though. If you pushed an infinite number of
object of whatever class, you'd eventually run out of memory.

I personally find #first() rather confusing (BTW [1,2,3].first
(3).class =3D> Array). I'd rather prefer [0..4] (although [0,5] should
perform slightly better) or maybe #each_index, which doesn't create an
intermediary array. #each_index would also have the advantage that it
expects only an Enumerable.

 

[James Gray]

First doesn't take an argument I'm ruby. It does
If you're using rails enumerable mixin

Blog: http://random8.zenunit.com/
Learn rails: http://sensei.zenunit.com/

Would you please stop top posting? It's just bad manners.

James Edward Gray II

 

[David A. Black]

Hi --

Hi --



Ryan had something like:

topics.first(5).each do |t|
puts t.title
end

which, I believe, does not create an intermediate array because
topics.first(5) returns an enumerator.

Rewind. As Tom points out, first(x) returns an array. (Which in fact
makes sense, since it's often used entirely on its own.)


David

--
David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Coming in 2009: The Well-Grounded Rubyist (http://manning.com/black2)

http://www.wishsight.com => Independent, social wishlist management!

 

[7stud --]

Slices and 'sub-arrays' aren't copies of the objects, they simply
refer to the identical objects.

Is it your opinion that an array of pointers takes up no memory? Which
takes up more memory: an array of int's or an array of pointers?

 

[Rick DeNatale]

[Note: parts of this message were removed to make it a legal post.]

Is it your opinion that an array of pointers takes up no memory? Which
takes up more memory: an array of int's or an array of pointers?

Well, an array of Fixnums takes up the same space as an array of 'pointers'
to Fixnums, since Fixnums are immediate.

 

[Ryan Davis]

First doesn't take an argument I'm ruby. It does
If you're using rails enumerable mixin

David showed it in 1.9... but I had to point this out:

% ruby -ve 'puts [1,2,3,4].first(2)'
ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]
1
2

this goes back to at least 1.7 iirc. #first was introduced in 1.6 and
1.7 gave it an optional length arg.

 

[Ryan Davis]

Would you please stop top posting? It's just bad manners.

agreed!

 

[Ryan Davis]

In my opinion, it's nicer than the first version because it doesn't
have
to create a sub array in memory, like all the solutions posted so far
do, which could be a problem with large arrays and large slices.

mentarbation.

it isn't a problem until it is a problem.

 

[David A. Black]

Hi --

First doesn't take an argument I'm ruby. It does
If you're using rails enumerable mixin

David showed it in 1.9... but I had to point this out:

% ruby -ve 'puts [1,2,3,4].first(2)'
ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]
1
2

this goes back to at least 1.7 iirc. #first was introduced in 1.6 and 1.7
gave it an optional length arg.

I've clearly got 1.9 on the brain


David

--
David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Coming in 2009: The Well-Grounded Rubyist (http://manning.com/black2)

http://www.wishsight.com => Independent, social wishlist management!