Ruby Regex to round trailing zeros

Question

I'm looking for a regex to remove trailing zeros from decimal numbers. It should return the following results:

0.0002300 -> 0.00023
10.002300 -> 10.0023
100.0     -> 100
1000      -> 1000
0.0       -> 0
0         -> 0

Basically, it should remove trailing zeros and trailing decimal point if the fraction part is 0. It should also return 0 when that's the value. Any thoughts? thanks.

Answer 1

Try the regex:

(?:(\..*[^0])0+|\.0+)$

and replace it with:

\1

A demo:

tests = ['0.0002300', '10.002300', '100.0', '1000', '0.0', '0']
tests.each { |tst|
  print tst, " -> ", tst.sub(/(?:(\..*[^0])0+|\.0+)$/, '\1'), "\n"
}

which produces:

0.0002300 -> 0.00023
10.002300 -> 10.0023
100.0 -> 100
1000 -> 1000
0.0 -> 0
0 -> 0

Or you could simply do "%g" % tst to drop the trailing zeros:

tests = ['0.0002300', '10.002300', '100.0', '1000', '0.0', '0']
tests.each { |tst|
  s = "%g" % tst
  print tst, " -> ", s, "\n"
}

which produces the same output.

Answer 2

just another way

["100.0","0.00223000"].map{|x|"%g"%x}

Answer 3

Here is bit more optimized regex solution.

Search for this regex:

(?:(\.[0-9]*[1-9])|\.)0+$

and replace with:

\1

RegEx Demo

RegEx Details:

• (?:: Start non-capture group
  • (\.[0-9]*[1-9]): Match a dot followed by 0+ instances of any digit and then a digit 1-9. Capture this value in group #1 (to be used in replacement back-reference \1)
  • |: OR
  • \.: Match a dot
• ): End non-capture group
• 0+: Match 1+ of zeroes
• $: End