Ruby: counting digits in a float number

Question

Is there any worthy Ruby method to count the number of digits in a float? Also, how do I specify the precise when to_s float numbers?

Keep in mind that the full number of digits in a float's decimal representation is not necessarily a useful number to have. For example, 0.1 is cannot be precisely represented in binary, so you might not be particularly happy to discover that 0.1 has 18 digits without rounding. — Chuck, Oct 02 '09 at 21:11

khelll · Accepted Answer · 2009-10-02T21:03:18.227

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# Number of digits

12345.23.to_s.split("").size -1 #=> 7

# The precious part

("." + 12345.23.to_s.split(".")[1]).to_f #=> .023

# I would rather used 
# 12345.23 - 12345.23.to_i 
# but this gives 0.22999999999563

edited Oct 02 '09 at 21:03

answered Oct 02 '09 at 20:51

khelll

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Your solution to count digits doesn't take into account the `'-'` on negative numbers. Also, what's your reasoning for doing `to_s.split("").size` instead of just doing `to_s.size`? – Pesto Oct 03 '09 at 12:48

score 2 · Answer 2 · answered May 30 '13 at 19:39

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to specify precision of a float in Ruby. you can use the round method.

number.round(2)

2 is the precision.

53.819.round(2) -> 53.82

answered May 30 '13 at 19:39

Postscripter

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like rails number_with_precision(precision: 3) just `"%.3f" % 53.82 => "53.820"` – YaEvan Feb 02 '21 at 07:29

score 1 · Answer 3 · answered Oct 02 '09 at 20:20

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I think you should check out the number_with_precision helper.

number_with_precision(13, :precision => 5) # => 13.00000

answered Oct 02 '09 at 20:20

Mike Buckbee

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I'm looking for the Ruby solution, not Rails – oldhomemovie Oct 02 '09 at 20:38

Ruby: counting digits in a float number

3 Answers3