Converting numeric string to numeric in Ruby - ruby

Question

I want a method like to_numeric(str) which convert numeric string 'str' into its numeric form else return nil. By numeric form if string is in integer method should return integer and it string is in float it should return float.
I have tried with following code. It works fine but need better solution if possible.
def to_numeric(str)
Integer(str)
rescue
Float(str) if Float(str) rescue nil
end
One important thing I forgot to mention is "I don't know the type of my input".
My use case:
arr = [1, 1.5, 2, 2.5, 4]
some_input = get_input_from_some_source
if arr.include?(to_numeric(some_input))
# do something
end

Answer 1

You can use BigDecimal#frac to achieve what you want
require 'bigdecimal'
def to_numeric(anything)
num = BigDecimal.new(anything.to_s)
if num.frac == 0
num.to_i
else
num.to_f
end
end
It can handle
#floats
to_numeric(2.3) #=> 2.3
#rationals
to_numeric(0.2E-4) #=> 2.0e-05
#integers
to_numeric(1) #=> 1
#big decimals
to_numeric(BigDecimal.new("2"))
And floats, rationals and integers in form of strings, too

Answer 2

Convert it to Float using String#to_f method. Since ruby using duck typing you may not care if it can be an Integer.
If it looks like a numeric, swims like a numeric and quacks like a numeric, then it probably is a numeric.
But be aware! to_f does not throw any exceptions:
"foobar".to_f # => 0

Answer 3

If you really insist to differentiate between Integer and Floats, then you can implement to_numeric like this:
def to_numeric(thing)
return thing.to_s.to_i if thing.to_s == thing.to_s.to_i.to_s
return thing.to_s.to_f if thing.to_s == thing.to_s.to_f.to_s
thing
end
It converts an object to an integer, if its string representation looks like an integer (same with float), or returns the unchanged thing if not:
['1', '1.5', 'foo', :bar, '2', '2.5', File].map {|obj| to_numeric obj}
# => [1, 1.5, "foo", :bar, 2, 2.5, File]

Answer 4

Here are some options:
Use floats for comparison:
arr = [1, 1.5, 2, 2.5, 4]
arr.include? "4.0".to_f #=> true
Use strings for comparison:
arr = %w(1 1.5 2 2.5 4)
arr.include? "4" #=> true
Use eval for conversion:
eval("4.0") #=> 4.0
eval("4") #=> 4
But you have to be very careful when using eval, see #tessi's comment.

Answer 5

def to_numeric(str)
str.include?(".") ? str.to_f : str.to_i
end