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Posted to users@groovy.apache.org by Søren Berg Glasius <so...@glasius.dk> on 2017/03/19 16:16:26 UTC
Re: float/double calculation bug ?
Hi,
This discussion does not belong on the dev mailing list, but the user
mailing list (*users@groovy.apache.org <us...@groovy.apache.org>)*. Please
continue your very interesting discussion there :-) Thanks.
/Søren
On Sun, 19 Mar 2017 at 16:47 James Bond <sb...@gmail.com> wrote:
What happens if you use .toDouble() instead of .toFloat, and an explicitly
double 100.0 literal? Right now, your computation is taking an integer,
dividing by a float, then multiplying by another float. I suspect that
going double precision won't fix this in all cases (floating point math is,
after all, just an approximation), but at least you're processing the
values as precisely as you can.
On Sun, Mar 19, 2017 at 8:28 AM, Derek Visch <de...@gmail.com> wrote:
Looks like floating point to me, what are you expecting?
On Mar 19, 2017 10:04 AM, "Tx. T" <tx...@yahoo.com> wrote:
Any idea why the follow code "calc" returns the "70%" of the 330000 incorrectly?
testing on: Groovy Version: 2.4.9 JVM: 1.8.0_112 Vendor: Oracle
Corporation OS: Mac OS X
Mac OS X 10.12.3
groovy:000> def calc = { amount, ttl ->
groovy:001> double rtn
groovy:002> if (amount[-1] != '%') rtn = amount.toDouble()
groovy:003> else rtn = ttl / 100.0 * amount.replaceAll(/%\Z/,
'').toFloat()
groovy:004>
groovy:004> rtn
groovy:005> }
===> groovysh_evaluate$_run_closure1@39fcbef6*groovy:000> calc("70%", 330000)
===> 230999.99999999997*
groovy:000> calc("10%", 330000)
===> 33000.0
groovy:000> calc("20%", 330000)
===> 66000.0
groovy:000> calc("30%", 330000)
===> 99000.0
groovy:000> calc("40%", 330000)
===> 132000.0
groovy:000> calc("50%", 330000)
===> 165000.0
groovy:000> calc("60%", 330000)
===> 198000.0*groovy:000> calc("70%", 330000)
===> 230999.99999999997*
groovy:000> calc("80%", 330000)
===> 264000.0
groovy:000> calc("90%", 330000)
===> 297000.0
groovy:000> calc("100%", 330000)
===> 330000.0
--
Best regards / Med venlig hilsen,
Søren Berg Glasius
Hedevej 1, Gl. Rye, 8680 Ry, Denmark
Mobile: +45 40 44 91 88, Skype: sbglasius
--- Press ESC once to quit - twice to save the changes.
Re: float/double calculation bug ?
Posted by Søren Berg Glasius <so...@glasius.dk>.
You are running into Floating point rounding in the JVM, which is not a
Groovy bug.
Your code can be salvaged by using BigDecimal:
def calc = { amount, ttl ->
BigDecimal rtn
if (amount[-1] != '%') rtn = amount.toBigDecimal()
else rtn = ttl / 100.0 * amount.replaceAll(/%\Z/, '').toBigDecimal()
rtn
}
On Sun, 19 Mar 2017 at 17:16 Søren Berg Glasius <so...@glasius.dk> wrote:
Hi,
This discussion does not belong on the dev mailing list, but the user
mailing list (*users@groovy.apache.org <us...@groovy.apache.org>)*. Please
continue your very interesting discussion there :-) Thanks.
/Søren
On Sun, 19 Mar 2017 at 16:47 James Bond <sb...@gmail.com> wrote:
What happens if you use .toDouble() instead of .toFloat, and an explicitly
double 100.0 literal? Right now, your computation is taking an integer,
dividing by a float, then multiplying by another float. I suspect that
going double precision won't fix this in all cases (floating point math is,
after all, just an approximation), but at least you're processing the
values as precisely as you can.
On Sun, Mar 19, 2017 at 8:28 AM, Derek Visch <de...@gmail.com> wrote:
Looks like floating point to me, what are you expecting?
On Mar 19, 2017 10:04 AM, "Tx. T" <tx...@yahoo.com> wrote:
Any idea why the follow code "calc" returns the "70%" of the 330000 incorrectly?
testing on: Groovy Version: 2.4.9 JVM: 1.8.0_112 Vendor: Oracle
Corporation OS: Mac OS X
Mac OS X 10.12.3
groovy:000> def calc = { amount, ttl ->
groovy:001> double rtn
groovy:002> if (amount[-1] != '%') rtn = amount.toDouble()
groovy:003> else rtn = ttl / 100.0 * amount.replaceAll(/%\Z/,
'').toFloat()
groovy:004>
groovy:004> rtn
groovy:005> }
===> groovysh_evaluate$_run_closure1@39fcbef6*groovy:000> calc("70%", 330000)
===> 230999.99999999997*
groovy:000> calc("10%", 330000)
===> 33000.0
groovy:000> calc("20%", 330000)
===> 66000.0
groovy:000> calc("30%", 330000)
===> 99000.0
groovy:000> calc("40%", 330000)
===> 132000.0
groovy:000> calc("50%", 330000)
===> 165000.0
groovy:000> calc("60%", 330000)
===> 198000.0*groovy:000> calc("70%", 330000)
===> 230999.99999999997*
groovy:000> calc("80%", 330000)
===> 264000.0
groovy:000> calc("90%", 330000)
===> 297000.0
groovy:000> calc("100%", 330000)
===> 330000.0
--
Best regards / Med venlig hilsen,
Søren Berg Glasius
Hedevej 1, Gl. Rye, 8680 Ry, Denmark
Mobile: +45 40 44 91 88 <40%2044%2091%2088>, Skype: sbglasius
--- Press ESC once to quit - twice to save the changes.
--
Best regards / Med venlig hilsen,
Søren Berg Glasius
Hedevej 1, Gl. Rye, 8680 Ry, Denmark
Mobile: +45 40 44 91 88 <40%2044%2091%2088>, Skype: sbglasius
--- Press ESC once to quit - twice to save the changes.