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Thread: Fraction conversion

Apr 28, 2009, 18:40 #1
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Fraction conversion
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.

Apr 28, 2009, 19:20 #2
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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.

Apr 29, 2009, 08:32 #3
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Ok but how do I convert user input = 3 3/4 to a string or array?

Apr 29, 2009, 14:18 #4
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Haven't we been over this already?
http://www.sitepoint.com/forums/showthread.php?t=611989

Apr 30, 2009, 10:33 #5
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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.

Apr 30, 2009, 11:28 #6
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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 ""

May 1, 2009, 05:04 #7
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The user would not need to put quote (") marks around the entry, and chomp in your "solution" does not remove quote marks:
http://www.rubydoc.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:
Code:puts "Enter something" entry = gets puts "Entry was of the type #{entry.class}"
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.

May 1, 2009, 05:11 #8
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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.
Code: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)
Code:puts "#{number} contains the number #{parts[1]} "
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:
Code:ft.test(number_to_test.chomp)

May 2, 2009, 18:40 #9
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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
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