0.06 == 0.06 returns false in Ruby?

ruby-talk
41

# > 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

···

From: Michael Ulm [mailto:michael.ulm@isis-papyrus.com]

42

Stefan Rusterholz wrote:

Marshal.dump on the other hand is serializing, of course you don't want
your floats truncated just because you're serializing.

Excuse me -- does Marshal.dump serialize floats in text or in binary?
I'd hope it was binary. A *YAML* serializer would have to do it in text,
although they could obviously encode binary in base 64 or hex.

43

Peña wrote:

From: Michael Ulm [mailto:michael.ulm@isis-papyrus.com] # > 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

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

Regards,

Michael

44

M. Edward (Ed) Borasky wrote:

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Hash: SHA1

Stefan Rusterholz wrote:

Marshal.dump on the other hand is serializing, of course you don't want your floats truncated just because you're serializing.

Excuse me -- does Marshal.dump serialize floats in text or in binary?
I'd hope it was binary. A *YAML* serializer would have to do it in text,
although they could obviously encode binary in base 64 or hex.

The number itself is in acsii:

irb(main):006:0> x = 1.234e120
=> 1.234e+120
irb(main):007:0> Marshal.dump(x)
=> "\004\bf\0371.2340000000000001e+120\000@`"

Maybe this is for compatibility, in case ruby is running on some oddball system without the standard float formats?

···

--
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

45

# > From: Michael Ulm [mailto:michael.ulm@isis-papyrus.com]
# > 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

···

From: Michael Ulm [mailto:michael.ulm@isis-papyrus.com]
#
# 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