Fraction conversion

[cberry1971]

I am working on allowing users to input measurements into a field and many will have fractions (eg. 3 5/6, 1/2, 4). Some user entries will just be a Fixnum.

The db table should store all user entered numbers as a integer by multiplying by 12 (eg 3 5/6 => 46, 1/2 => 6, 4 => 48).

How would I go about taking a user entry and converting it to the "entry" x 12 integer for the db?

Many thanks.

[Mittineague]

You could "split" the numbers by a space and then by a slash. Then do the division to get a float, add to the whole number, and multiply by 12.

I don't know about precision, but if you have a restricted number of possible input variations (i.e. only #/2, #/3, #/4, #/6 and #/12) I think you should be OK.

[cberry1971]

Ok but how do I convert user input = 3 3/4 to a string or array?

[ReggieB]

Haven't we been over this already?

http://www.sitepoint.com/forums/showthread.php?t=611989

[cberry1971]

Thanks Regggie... but the case was not solved earlier as one needed to put " " around the user input in your cases. I am trying to avoid a user from having to input "1 1/2" but simply 1 1/2. You have been great and I feel like I am on the 1 yard line but need to get rid of the quotes.

[cberry1971]

OK I solved my own problem of getting rid of the "" marks.

in the link one would use the following code:

ft = FractionTest.new
number = gets.chomp
ft.test(number)

That way the user does not need to input with ""

[ReggieB]

The user would not need to put quote (") marks around the entry, and chomp in your "solution" does not remove quote marks:

http://www.ruby-doc.org/core/classes...g.html#M000834

What needs to happen is that the input needs to be in the form of a string. Most user inputs will be in the form of a string. For example, try running this code:

puts "Enter something"
entry = gets
puts "Entry was of the type #{entry.class}"

Run this twice. First entering "1 1/2" and the other just 1 1/2
You'll see that both entries are input into the program as strings. The same is the case with HTML forms. The entry is received via HTTP as a string, with or without quotes.

If chomp has fixed the problem, it appears that a carriage return or end of line character is causing the problem.

[ReggieB]

Actually, even better try running this version of my program and your see that inputs of 1 1/2 and "1 1/2" both work and both give the same answer.

class FractionTest
  NUMBER_AND_FRACTION = /(\d+)\s+(\d+\/\d+)/
  FRACTION_ONLY = /(\d+)\/(\d+)/
  NUMBER_ONLY = /(\d+\.*\d*)/

  def test(number)
    case number
    when NUMBER_AND_FRACTION
      number_and_fraction(number)
    when FRACTION_ONLY
      fraction_only(number)
    when NUMBER_ONLY
      number_only(number)
    else
      puts "no match"
    end
    puts "--------------"
  end

  private

  def number_and_fraction(number)
    parts = number.match(NUMBER_AND_FRACTION)
    result = parts[1].to_f + process_fraction(parts[2])
    puts "#{number} contains the number #{parts[1]} "
    puts "and the fraction #{parts[2]} "
    puts "and is equal to #{result}."
  end

  def fraction_only(number)
    result = process_fraction(number)
    puts "#{number} contains the fraction #{number} "
    puts "and is equal to #{result}."
  end

  def number_only(number)
    result = number.match(NUMBER_ONLY)[0].to_f
    puts "#{number} contains the number #{number}"
    puts "and is equal to #{result}."
  end

  def process_fraction(fraction)
    parts = fraction.match(FRACTION_ONLY)
    numerator = parts[1].to_f
    denominator = parts[2].to_f
    return numerator / denominator
  end

end

ft = FractionTest.new

puts "Enter a number"
number_to_test = gets
ft.test(number_to_test)

Actually, playing with that I notice that there is a formatting issue as the gets is recovering the end of line character and that is causing my output to step down a line at this point:

puts "#{number} contains the number #{parts[1]} "

So 1 1/2 is generating:

1 1/2
contains the number 1

Instead of the intended

1 1/2 contains the number 1

And indeed a chomp fixes that for example by altering the last line to:

ft.test(number_to_test.chomp)

[cberry1971]

I have been scouring the web to try to avoid having to ask how to make the fraction conversion in the model. I have the following code and keep getting a "dynamic constant assignment" error:

class Food < ActiveRecord::Base
attr_accessor :quantity
before_save :convert_quantity

private

def convert_quantity
quantity = @quantity
self.quantity = convert(quantity)
end

def FractionConversion
NUMBER_AND_FRACTION = /(\d+)\s+(\d+\/\d+)/
FRACTION_ONLY = /(\d+)\/(\d+)/
NUMBER_ONLY = /(\d+\.*\d*)/

def convert(number)
case number
when NUMBER_AND_FRACTION
number_and_fraction(number)
when FRACTION_ONLY
fraction_only(number)
when NUMBER_ONLY
number_only(number)
else
puts "no match"
end
puts "----------"
end

... to the end of the convert