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

Cavite

Did you try this convert method? It works for the 4 cases you provided. – Ardisardisj

Answer 1

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"
strip_trailing_zero(250)   # => "250"

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.

Obel

if you pass it integer then it will also remove 0 from an integer value, so don't pass it integer values "20" => 2 – Gendarmerie

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. – Obel

You need to remove the question mark from regex n.to_s.sub(/\.0+$/, '') – Vaporous

This DOES NOT WORK strip_trailing_zero(250) => "25" – Monzon

It did when the question was asked and answered. Ruby has changed. – Obel

If you are working with rails, you may check the number_with_precision method from ActionView/Helpers/NumberHelper – Phytosociology

@theTinMan: Ruby hasn't changed. The regex, /\.?0+$/ says "Maybe there's a ., maybe not, followed by one or more 0." Your replacement would turn "250" (Not a ., but one 0) into "25" in any language. – Weekend

Answer 2

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"

Trinh

0 comes to -0 with %g – Berneta

Be careful! It looks like it works but if you pass 21385524.0031 You'll get: 2.13855e+07 – Monzon