Trim a trailing .0

This should cover your needs in most cases: some_value.gsub(/(\.)0+$/, '').

It trims all trailing zeroes and a decimal point followed only by zeroes. Otherwise, it leaves the string alone.

It's also very performant, as it is entirely string-based, requiring no floating point or integer conversions, assuming your input value is already a string:

Loading development environment (Rails 3.2.19)
irb(main):001:0> '123.0'.gsub(/(\.)0+$/, '')
=> "123"
irb(main):002:0> '123.000'.gsub(/(\.)0+$/, '')
=> "123"
irb(main):003:0> '123.560'.gsub(/(\.)0+$/, '')
=> "123.560"
irb(main):004:0> '123.'.gsub(/(\.)0+$/, '')
=> "123."
irb(main):005:0> '123'.gsub(/(\.)0+$/, '')
=> "123"
irb(main):006:0> '100'.gsub(/(\.)0+$/, '')
=> "100"
irb(main):007:0> '127.0.0.1'.gsub(/(\.)0+$/, '')
=> "127.0.0.1"
irb(main):008:0> '123xzy45'.gsub(/(\.)0+$/, '')
=> "123xzy45"
irb(main):009:0> '123xzy45.0'.gsub(/(\.)0+$/, '')
=> "123xzy45"
irb(main):010:0> 'Bobby McGee'.gsub(/(\.)0+$/, '')
=> "Bobby McGee"
irb(main):011:0>

For those using Rails, ActionView has the number_with_precision method that takes a strip_insignificant_zeros: true argument to handle this.

number_with_precision(13.00, precision: 2,  strip_insignificant_zeros: true)
# => 13
number_with_precision(13.25, precision: 2,  strip_insignificant_zeros: true)
# => 13.25

See the number_with_precision documentation for more information.

def trim num
  i, f = num.to_i, num.to_f
  i == f ? i : f
end

trim(2.5) # => 2.5
trim(23) # => 23

or, from string:

def convert x
  Float(x)
  i, f = x.to_i, x.to_f
  i == f ? i : f
rescue ArgumentError
  x
end

convert("fjf") # => "fjf"
convert("2.5") # => 2.5
convert("23") # => 23
convert("2.0") # => 2
convert("1.00") # => 1
convert("1.10") # => 1.1