CODEWITHSUNDEEP
rubydecimalrounding
Blankman
Blankman

Reputation: 266940

I have a numeric value like 30.6355 that represents money, how to round to 2 decimal places?

I have a numeric value like 30.6355 that represents money, how to round to 2 decimal places?

Upvotes: 4

Views: 5820

Answers (3)

The Dembinski
The Dembinski

Reputation: 1519

This will round for some useful cases - not well written but it works! Feel free to edit.

def round(numberString)
numberString = numberString.to_s
decimalLocation = numberString.index(".")
numbersAfterDecimal = numberString.slice(decimalLocation+1,numberString.length-1)
numbersBeforeAndIncludingDeciaml = numberString.slice(0,decimalLocation+1)

if numbersAfterDecimal.length <= 2
    return numberString.to_f
end

thingArray = numberString.split("")
thingArray.pop

prior = numbersAfterDecimal[-1].to_i
idx = numbersAfterDecimal.length-2

thingArray.reverse_each do |numStr|
    if prior >= 5
        numbersAfterDecimal[idx] = (numStr.to_i + 1).to_s unless (idx == 1 && numStr.to_i == 9)
        prior = (numStr.to_i + 1)
    else
        prior = numStr.to_i
    end
    break if (idx == 1)
    idx -= 1
end

resp = numbersBeforeAndIncludingDeciaml + numbersAfterDecimal[0..1]
resp.to_f
end

round(18.00) == 18.0

round(18.99) == 18.99

round(17.9555555555) == 17.96

round(17.944444444445) == 17.95

round(15.545) == 15.55

round(15.55) == 15.55

round(15.555) == 15.56

round(1.18) == 1.18

round(1.189) == 1.19

Upvotes: 0

Reese Moore
Reese Moore

Reputation: 11640

Ruby 1.8:

class Numeric
    def round_to( places )
        power = 10.0**places
        (self * power).round / power
    end
end

(30.6355).round_to(2)

Ruby 1.9: 

(30.6355).round(2)

In 1.9, round can round to a specified number of digits.

Upvotes: 13

lucasrizoli
lucasrizoli

Reputation: 638

You should not use double or float types when dealing with currency: they have both too many decimal places and occasional rounding errors. Money can fall through those holes and it'll be tough to track down the errors after it happens.

When dealing with money, use a fixed decimal type. In Ruby (and Java), use BigDecimal.

Upvotes: 20

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