Precision and ==

Ruby
1

We all know that finite representation comes with some difficulties…
but…

x = 45.0*(Math::PI / 180.0)
y = 0.785398163397448
puts “#{x.class} : #{x}”
puts “#{y.class} : #{y}”
puts 45.0*(Math::PI / 180.0) == 0.785398163397448

prints

Float : 0.785398163397448
Float : 0.785398163397448
false

Does to_s show something less precise than the internal representation
of
Floats?

thx
Bernard

2

On Wed, Apr 7, 2010 at 1:02 PM, LAMBEAU Bernard [email protected]
wrote:

Float : 0.785398163397448
Float : 0.785398163397448
false

Does to_s show something less precise than the internal representation of
Floats?

Yes, it rounds to 15 decimal positions:

irb(main):001:0> x = 45.0*(Math::PI / 180.0)
=> 0.785398163397448
irb(main):002:0> y = 0.785398163397448
=> 0.785398163397448
irb(main):003:0> puts “#{x.class} : #{”%.20f" % x}"
Float : 0.78539816339744827900
=> nil
irb(main):004:0> puts “#{y.class} : #{”%.20f" % y}"
Float : 0.78539816339744794593

Jesus.