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in reply to Re^2: Help me make a test case for Math::BigFloat
in thread Help me make a test case for Math::BigFloat

Hmm. There seem to be two interacting problems here.

  1. exp doesn't appear to be overloaded by either bignum or Math::BigFloat?
    #!perl -slw use strict; use overload; #use bignum; use Math::BigFloat; printf "exp(-7e-17): %.17f\n", my $exp = exp( Math::BigFloat->new( '-7 +e-17' ) ); eval{ print overload::Overloaded( $exp ) } or warn $@; print overload::StrVal( $exp ); printf "1-exp(-7-e17): %.17f\n", Math::BigFloat->new("1") - $exp; __END__ C:\test>junk7 exp(-7e-17): 0.99999999999999989 Can't call method "can" without a package or object reference at c:/Pe +rl/lib/overload.pm line 54. 1 1-exp(-7-e17): 0.00000000000000000
  2. And with bignum enabled, Math::BigFloat seems to forget how to do math? At least if the math involves one BigMath object and one normal perl number.
    #!perl -slw use strict; use overload; use bignum; use Math::BigFloat; printf "exp(-7e-17): %.17f\n", my $exp = exp( Math::BigFloat->new( '-7 +e-17' ) ); eval{ print overload::Overloaded( $exp ) } or warn $@; print overload::StrVal( $exp ); printf "1-exp(-7-e17): %.17f\n", Math::BigFloat->new("1") - $exp; __END__ C:\test>junk7 exp(-7e-17): 0.99999999999999989 Can't call method "can" without a package or object reference at c:/Pe +rl/lib/overload.pm line 54. 1 1-exp(-7-e17): 1.00000000000000000

All of which makes me glad that I rarely need the accuracy beyond 53-bits and when I do, 64-bit ints suffice.


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