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Re: Strange int() result

by Laurent_R (Abbot)
on Jun 18, 2014 at 18:04 UTC ( #1090324=note: print w/replies, xml ) Need Help??

in reply to Strange int() result

I think the solution proposed by Athanasius is probably best. But if you want to use a regex, this one is simpler than yours:
$amount =~ s/\.//;

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Re^2: Strange int() result
by flowdy (Scribe) on Jun 18, 2014 at 19:51 UTC

    It is no use in simply removing the dot. Probably you mean $amount =~ s/\..+//? int() is faster.

      How so? The OP's problem comes from the use of int function on a number calculated as 35784.45 * 100 and turning out to be very very slightly smaller than 3578445. It seems to me you probably read too quickly the OP. Example under the debugger:
      DB<10> $amount = 35784.45; DB<11> $amount =~ s/\.//; DB<12> print $amount; 3578445
        Very interesting test! I could not understand at first why multiplying with an even integer factor would introduce rounding errors. So it seemed, but when I went one step back and ignored the multiplication I saw: the value itself is not expressible as a fixedpoint binary number.

        So there are two ways to look at it (numerically and as a string):

        $ perl -wE '$x=35784.45; printf "%.15f\n%s", $x, $x;' 35784.449999999997090 35784.45

        Since now I always assumed the string representation were made from the numerical representation thus giving the same output. That was obviously wrong.


        A second counter test

        $ perl -wE '$x=35784.449999999997090; printf "%.15f\n%s", $x, $x;' 35784.449999999997090 35784.45
        reveals: the string representation always uses some rounding.
        Thanks, got the point. Shame on me.

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