0.06 == 0.06 returns false in Ruby?

Ruby
41

Peña wrote:

  BigDecimal.new(self.to_s)

=> true

z==y
=> true
x==z
=> true
z==x
=> true
–snip–

However (among other problems):

x = (1.0/3.0).to_dec
y = 1.0.to_dec / 3.0.to_dec
x == y # => false

HTH,

Michael

42

From: Michael U. [mailto:[email protected]]

> x = 1.0.to_dec / 3.0.to_dec

> y = x + x + x

> y == 1.0.to_dec # => false

hmm, i thought this was already answered by others… gotta check…

irb(main):023:0* x=1.0.to_dec/3.0.to_dec
=> #<BigDecimal:b7e45e14,‘0.3333333333 333333E0’,16(24)>
irb(main):024:0> x+x+x == 1.0.to_dec
=> true

kind regards -botp

43

Peña wrote:

=> true
Strange, I tested this on two different machines and both gave false
to your last expression. Did you modify BigDecimal#== ?

Regards,

Michael

44

This is why I prefer to use fixed decimal. In your own private code,
it’s easy enough to implement. You just decide how many “decimals” your
int’s should have.

Getting correct programs using floats are really hard. Heck, MS Excell
don’t even get Sum and Mean right. (Microsoft, usually, use naïve
algorithm’s that don’t take care of underflow and rounding errors).

45

From: Michael U. [mailto:[email protected]]

> From: Michael U. [mailto:[email protected]]

> irb(main):023:0* x=1.0.to_dec/3.0.to_dec

> => #<BigDecimal:b7e45e14,‘0.3333333333 333333E0’,16(24)>

> irb(main):024:0> x+x+x == 1.0.to_dec

> => true

Strange, I tested this on two different machines and both gave false

to your last expression. Did you modify BigDecimal#== ?

yes. i just used one of the codes posted here… not sure if it was even
your suggested code though. nonetheless, what were you expecting? that
1/3 can be represented exactly in decimal? :slight_smile:
but i really want a way to override float literals, so i do not litter
all those to_decs :)) Of course, floats has a lot of merits, but it
gives too many surprises fr just a few dec samples. businesswise, it has
little use.

kind regards -botp