Set the display precision of a float in Ruby
RubyFloating PointPrecisionRuby Problem Overview
Is it possible to set the display precision of a float in Ruby?
Something like:
z = 1/3
z.to_s #=> 0.33333333333333
z.to_s(3) #=> 0.333
z.to_s(5) #=> 0.33333
Or do I have to override the to_s method of Float?
Ruby Solutions
Solution 1 - Ruby
z.round(2) or x.round(3) is the simplest solution. See http://www.ruby-doc.org/core-1.9.3/Float.html#method-i-round.
That said, that will only ensure that it is no more than that many digits. In the case of 1/3 that is fine, but if you had say 0.25.round(3) you will get 0.25, not 0.250.
Solution 2 - Ruby
You can use sprintf:
sprintf("%0.02f", 123.4564564)
Solution 3 - Ruby
I would normally just do the conversion in open code, something like:
puts "%5.2f" % [1.0/3.0]
Ruby calls Kernel#format for expressions like this, because String has a core operator % defined on it. Think of it as printf for Ruby if that rings any bells for you.
Solution 4 - Ruby
Rubocop recommends using #format over #sprintf and using annotated string tokens.
The syntax for #format is
%[flags][width][.precision]type
Example:
# Ensure we store z as a float by making one of the numbers a float.
z = 1/3.0
# Format the float to a precision of three.
format('%<num>0.3f', num: z)
# => "0.333"
format('%<num>0.5f', num: z)
# => "0.33333"
# Add some text to the formatted string
format('I have $%<num>0.2f in my bank account.', num: z)
# => "I have $0.33 in my bank account."
References:
Solution 5 - Ruby
You can use puts
z = #{'%.3f' % z}