Floating-point cheat sheet for Ruby

Floating-Point Types

Ruby floats are mapped to double-precision IEEE 754.

	f = 0.1

Ruby has an arbitrary-precision decimal type named BigDecimal in the bigdecimal module, which also allows to choose the rounding mode.

	require 'bigdecimal'

	a = BigDecimal('0.1')
	b = BigDecimal('0.2')
	c = a + b # returns a BigDecimal representing exactly 0.3

To get a string:

	"%.2f" % 1.2399 # returns "1.24"
	"%.3f" % 1.2399 # returns "1.240"
	"%.2f" % 1.2 # returns "1.20"

To print to standard output:

	puts "%.2f" % 1.2399