Set the display precision of a float in Ruby

ruby floating-point precision
salt.racer picture salt.racer · Dec 19, 2009 · Viewed 73k times · Source

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?

Answer

DrewB picture DrewB · Aug 7, 2012

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.

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