Is it the ruby way to implement #downto

ruby-talk
1

Hi all,

I wonder if the following code is the ruby way to implement
Integer#downto.

Thanks,

Li

···

#######################
class Integer
  def my_downto(final=2)
    for i in (final..self).to_a.reverse
      yield i
      end
   end
end

10.my_downto(-1) do |i| puts i end
--
Posted via http://www.ruby-forum.com/.

2

Well, I'd hope that creating 3 unnecessary objects wouldn't be deemed
the Ruby way :^)
Most code I've seen would use each() instead of for i in (). Each is
faster anyways.

Why not use the bastardized C way:

class Integer
def my_downto(final=2)
     i = self
     while i >= final
      yield i
      i-=1
     end
   end
end

I don't believe the Ruby community has shunned the idea of writing C
in ruby have they?

-Skye

···

On Jun 23, 8:36 am, Li Chen <chen_...@yahoo.com> wrote:

Hi all,

I wonder if the following code is the ruby way to implement
Integer#downto.
#######################
class Integer
def my_downto(final=2)
for i in (final..self).to_a.reverse
yield i
end
end
end

10.my_downto(-1) do |i| puts i end

3

Skye Shaw!@#$ wrote:

Well, I'd hope that creating 3 unnecessary objects wouldn't be deemed
the Ruby way :^)
Most code I've seen would use each() instead of for i in (). Each is
faster anyways.

I do it this way using each().

def my_downto2(final=2)
      (final..self).to_a.reverse.each do |i| yield i end
end

But I am still uncomfortable that I have to use #to_a followed by
#reverse to do the trick. Besides using while loops what is the best way
to add a new method of #downto?

Thanks,

Li

···

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

4

Hi --

Hi all,

I wonder if the following code is the ruby way to implement
Integer#downto.
#######################
class Integer
def my_downto(final=2)
for i in (final..self).to_a.reverse
yield i
end
end
end

10.my_downto(-1) do |i| puts i end

Well, I'd hope that creating 3 unnecessary objects wouldn't be deemed
the Ruby way :^)
Most code I've seen would use each() instead of for i in (). Each is
faster anyways.

Why not use the bastardized C way:

class Integer
def my_downto(final=2)
    i = self
    while i >= final
     yield i
     i-=1
    end
  end
end

I don't believe the Ruby community has shunned the idea of writing C
in ruby have they?

I think most of us shun doing the heavy lifting when Ruby can do it
for us :slight_smile: There's nothing C-specific about using an explicit loop
variable, but it's pretty uncommon in Ruby code, except when doing
exercises like implementing each without recourse to each and things
like that.

I'd be tempted to do something like:

   def my_downto(n)
     (self-n+1).times {|x| yield self-x }
     self
   end

I don't know how it performs compared to the others.

David

···

On Wed, 24 Jun 2009, Skye Shaw!@#$ wrote:

On Jun 23, 8:36 am, Li Chen <chen_...@yahoo.com> wrote:

--
David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Now available: The Well-Grounded Rubyist (http://manning.com/black2\)
"Ruby 1.9: What You Need To Know" Envycasts with David A. Black
http://www.envycasts.com

5

Hi --

···

On Wed, 24 Jun 2009, Li Chen wrote:

Skye Shaw!@#$ wrote:

Well, I'd hope that creating 3 unnecessary objects wouldn't be deemed
the Ruby way :^)
Most code I've seen would use each() instead of for i in (). Each is
faster anyways.

I do it this way using each().

def my_downto2(final=2)
     (final..self).to_a.reverse.each do |i| yield i end
end

But I am still uncomfortable that I have to use #to_a followed by
#reverse to do the trick. Besides using while loops what is the best way
to add a new method of #downto?

def my_downto(n)
   (-self..-n).each {|i| yield -i }
   self
end

:slight_smile:

David

--
David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Now available: The Well-Grounded Rubyist (http://manning.com/black2\)
"Ruby 1.9: What You Need To Know" Envycasts with David A. Black
http://www.envycasts.com

6

David A. Black wrote:

def my_downto(n)
   (-self..-n).each {|i| yield -i }
   self
end

:slight_smile:

David

Hi David,

Thank you so much,

Li

···

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