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 01112013, 05:34 AM #1Member
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How to enclose certain digits of a value double in parentheses
I need to make a program that converts fractions to decimal form, but cuts it off after a certain amount of digits, and then repeating decimals after that need to be closed in parentheses. I have most of it done, but the part I'm stumped with is how to enclose the repeating digits in parentheses (Strings are not my strong point
here's my code so far:
Java Code:import java.math.RoundingMode; import java.text.DecimalFormat; import java.util.Scanner; public class fractions { public static void main(String[] args) { double num = 0, denom = 0; double dec = 0; Scanner numerator = new Scanner(System.in); Scanner denominator = new Scanner(System.in); System.out.println("Enter a fraction, each side no more than 2 digits: "); num+=numerator.nextInt(); denom+=numerator.nextInt(); dec = num / denom; double d = dec; DecimalFormat df = new DecimalFormat("0.##"); df.setRoundingMode(RoundingMode.DOWN); double outputNum = Double.valueOf(df.format(d)); String outputString = df.format(d); System.out.println("The decimal form is: " +outputString); } }
 01112013, 05:42 AM #2Senior Member
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Re: How to enclose certain digits of a value double in parentheses
Just to clarify, you want the output to look something like this?
Java Code:8.3333(333)
 01112013, 10:12 AM #3AN21XX
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Re: How to enclose certain digits of a value double in parentheses
How about this:
 Declare a helper string
 Look for the dot in the formatted number string
 Copy all until that digit (the one you want to start with) in the helper
 Append a opening bracket to helper
 Copy the rest of the string to the end of the helper
 Append a closing bracketLast edited by Sierra; 01112013 at 03:21 PM.
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 01112013, 03:10 PM #4Member
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 01112013, 03:22 PM #5AN21XX
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Re: How to enclose certain digits of a value double in parentheses
How do you determine at which point they repeat? What is your criteria? e.g. for 6.88888889 ?
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 01112013, 03:39 PM #6Member
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Re: How to enclose certain digits of a value double in parentheses
Here's a link to the actual problem, it can probably explain better than me:
https://www.dropbox.com/s/ufej8xxhxr...2fractions.pdf
 01112013, 04:57 PM #7AN21XX
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Re: How to enclose certain digits of a value double in parentheses
Well I am not asking for the assignment but for your approach to the solution... ;)
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 01112013, 05:15 PM #8Member
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 01112013, 05:59 PM #9
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Re: How to enclose certain digits of a value double in parentheses
Maybe the following (very old) algorithm can be of help: it finds the repeating group of digits for a number 1/p where p is prime (not equal to 2 or 5). It has its origins in Vedic math (a very interesting topic).
Without any proof:
Java Code:public class RepFracs { public static void main(String[] args) { int prime= 7; int multiplier, factor; for (multiplier= 1; ; multiplier++) if ((prime*multiplier)%10 == 9) { factor= (prime*multiplier)/10; if (++factor == 10) factor=1; break; } int length= 0, x=multiplier, carry= 0; StringBuilder sb= new StringBuilder(); do { sb.append(""+x); x*= factor; x+= carry; carry= x/10; x= x%10; length++; } while (x != multiplier  carry != 0); System.out.println(length+" "+sb.reverse()); } }
JosLast edited by JosAH; 01112013 at 06:07 PM.
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 01142013, 05:42 AM #10Member
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 01142013, 07:50 AM #11
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Re: How to enclose certain digits of a value double in parentheses
The only person who got everything done by Friday was Robinson Crusoe.
 01172013, 01:02 AM #12Member
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 01172013, 08:25 AM #13
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