Rails - Jan 2006 - Formatting a float with a set number of decimals

Another newbie question:

How do i convert a float to a string, rounded to a certain number of 
decimals?

Thanks

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

Is this it?
sprintf("%0.2f",10.12345)

Is there a better way?

chris hulbert wrote:
> Another newbie question:
> 
> How do i convert a float to a string, rounded to a certain number of 
> decimals?
> 
> Thanks

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

Chris:

I don''t KNOW the answers to your question (which may lead you to  
wonder why I wrote). Depending on the situation, I''d suggest you look  
up one of these two.

There is a helper called number_with_precision. It works like this,  
if x is the number

number_with_precision(x, number of decimal places)

To convert a number to a string, assuming the number was x

x.to_s

Hope that helps. People on this list are always helping me.

bruce


On 16-Jan-06, at 10:38 PM, chris hulbert wrote:
> Is this it?
> sprintf("%0.2f",10.12345)
>
> Is there a better way?
>
> chris hulbert wrote:
>> Another newbie question:
>>
>> How do i convert a float to a string, rounded to a certain number of
>> decimals?
>>
>> Thanks
>
>
> -- 
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails

On Tuesday 17 Jan 2006 05:38, chris hulbert wrote:
> Is this it?
> sprintf("%0.2f",10.12345)
> Is there a better way?
Assuming you''re dealing with currency, in my case it''s GBP (so
you can replace
the £ with $ or Euro whatever you need), but here''s what I
have in my
application_helper.rb

def display_currency(number)
  unless number.nil?
    "£" + sprintf("%01.2f",number)
  end
end

Then in my views I can just do:

<%= display_currency @price %>

~Dave

-- 

Dave Silvester
Rent-A-Monkey Website Development
Web: http://www.rentamonkey.com/

chris hulbert wrote:
> Another newbie question:
> 
> How do i convert a float to a string, rounded to a certain number of 
> decimals?
> 
> Thanks
This works...

"%5.2f" % number

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

Thanks for all the input, i ended up with this, and indeed it is for 
currency:

	def n(number,dec_places=0,divide_by=-1)
		# given a number, rounds it, divides it by Y and stringifies it
		# or if it is infinite, returns an ''x''
		if !number.nil? && (!(number.kind_of? Float) || number.finite?)
			v = number
			v /= divide_by if divide_by != -1
			if v >= 0 then
				"%.#{dec_places}f" % v + " "
			else
				"(%.#{dec_places}f)" % (-v)
			end
		else
			''x ''
		end
	end

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

chris hulbert wrote:
> Thanks for all the input, i ended up with this, and indeed it is for 
> currency:
> 
> 	def n(number,dec_places=0,divide_by=-1)
> 		# given a number, rounds it, divides it by Y and stringifies it
> 		# or if it is infinite, returns an ''x''
> 		if !number.nil? && (!(number.kind_of? Float) || number.finite?)
> 			v = number
> 			v /= divide_by if divide_by != -1
> 			if v >= 0 then
> 				"%.#{dec_places}f" % v + " "
> 			else
> 				"(%.#{dec_places}f)" % (-v)
> 			end
> 		else
> 			''x ''
> 		end
> 	end
Lots of problems here..

1. will break if you divide by zero
2. Should check to see if number is a subclass of Integer instead of not 
a Float
3. if number is an Integer, when you divide by divide_by, you will 
truncate the the value instead of rounding.

_Kevin

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

Chris, I had a similar requirement (be able to round to arbitrary
amount of decimals). What I did was made a very simple plugin with one
class in it:

class Float
  alias original_round round
  def round(precision = 0)
    if precision == 0
      original_round
    else
      sprintf("%.#{precision}f", self).to_f
    end
  end
end

This overrides the Float class so now you can just do:
23.43.round  #=23
23.43.round(1)  #= 23.4
etc....

It works like a champ. Dont know if there would be any issues with it
in the long run, but couldn''t think of any.

-Nick

p.s. just thought, I should probably and a check for negative
percision, but why would anyone want to even try that? :)

On 1/17/06, chris hulbert <chris.hulbert@ruralpress.com>
wrote:
> Thanks for all the input, i ended up with this, and indeed it is for
> currency:
>
>         def n(number,dec_places=0,divide_by=-1)
>                 # given a number, rounds it, divides it by Y and
stringifies it
>                 # or if it is infinite, returns an ''x''
>                 if !number.nil? && (!(number.kind_of? Float) ||
number.finite?)
>                         v = number
>                         v /= divide_by if divide_by != -1
>                         if v >= 0 then
>                                 "%.#{dec_places}f" % v +
"&nbsp;"
>                         else
>                                 "(%.#{dec_places}f)" % (-v)
>                         end
>                 else
>                         ''x&nbsp;''
>                 end
>         end
>
> --
> Posted via http://www.ruby-forum.com/.
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> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

Nick Stuart wrote:
> 
> It works like a champ. Dont know if there would be any issues with it
> in the long run, but couldn''t think of any.
> 
> -Nick
> 
> p.s. just thought, I should probably and a check for negative
> percision, but why would anyone want to even try that? :)
You should check for a decimal precision too...

_Kevin

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

Hrmmm, that would be good too. Of course right now I''m the only
developer in my company, and I know better.   :)
*famous last words*

On 1/17/06, Kevin Olbrich <kevin.olbrich@duke.edu>
wrote:
> Nick Stuart wrote:
> >
> > It works like a champ. Dont know if there would be any issues with it
> > in the long run, but couldn''t think of any.
> >
> > -Nick
> >
> > p.s. just thought, I should probably and a check for negative
> > percision, but why would anyone want to even try that? :)
>
> You should check for a decimal precision too...
>
> _Kevin
>
> --
> Posted via http://www.ruby-forum.com/.
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> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>