Ruby code to remove insignificant decimal places?

Question

I would like to get an elegant code, which removes the insignificant closing zeroes, eg:

29.970 => 29.97
29.97 => 29.97
25.00 => 25
25.0 => 25

I tried:

argument.to_r.to_f.to_s

But doesn't work in every cases, eg on 25.00 gives 25.0

Did you try [this `convert` method](http://stackoverflow.com/a/18533211/1241782)? It works for the 4 cases you provided. — Mike S, Jun 17 '16 at 22:15

the Tin Man · Accepted Answer · 2016-06-17T23:29:05.373

15

Trailing zeros are only significant when the number is a string:

def strip_trailing_zero(n)
  n.to_s.sub(/\.?0+$/, '')
end

strip_trailing_zero(29.970) # => "29.97"
strip_trailing_zero(29.97)  # => "29.97"
strip_trailing_zero(25.00)  # => "25"
strip_trailing_zero(25.0)   # => "25"

This converts the incoming floating point numbers and converts them into a string, then uses a simple sub search and replace to trim the trailing 0 and optionally the decimal point.

You can figure out how to convert them back to integers and floats if that's necessary. This will remove significant trailing zeros if you pass a integer/fixnum. How to guard against that is also something for you to figure out.

edited Jun 17 '16 at 23:29

answered Jun 17 '16 at 22:36

the Tin Man

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if you pass it integer then it will also remove 0 from an integer value, so don't pass it integer values "20" => 2 – Iqbal Khan Nov 28 '19 at 06:54
Since the point was to remove trailing zeroes from floating point then it shouldn't get passed an integer. It'd be an easy thing to protect against though. – the Tin Man Nov 29 '19 at 03:29
4

You need to remove the question mark from regex n.to_s.sub(/\.0+$/, '') – Petran Oct 28 '20 at 12:50
1

This DOES NOT WORK strip_trailing_zero(250) => "25" – Handsome Jack Sep 28 '22 at 12:28
It did when the question was asked and answered. Ruby has changed. – the Tin Man Nov 28 '22 at 18:55

score 7 · Answer 2 · answered Jun 30 '21 at 03:56

7

Try sprintf('%g', value_here) ?

`g` ->  Convert a floating point number using exponential form
  | if the exponent is less than -4 or greater than or
  | equal to the precision, or in dd.dddd form otherwise.

https://apidock.com/ruby/Kernel/sprintf

sprintf('%g',29.970) # => "29.97"
sprintf('%g',29.97)  # => "29.97"
sprintf('%g',25.00)  # => "25"
sprintf('%g',25.0)   # => "25"

answered Jun 30 '21 at 03:56

aldrien.h

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1

0 comes to -0 with %g – K2xL Jul 14 '21 at 00:24
1

Be careful! It looks like it works but if you pass 21385524.0031 You'll get: 2.13855e+07 – Handsome Jack Sep 28 '22 at 12:28

Ruby code to remove insignificant decimal places?

2 Answers2