Vincent Lefevre on Tue, 02 Oct 2007 10:15:14 +0200

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some dilog values are complex instead of being real


With Pari 2.3.2:

? dilog(-1)
%1 = -0.8224670334241132182362075834 + 9.136285398175292265776793780 E-29*I

but the value should be a real number. I suppose that the imaginary
term is due to a rounding error, in which case it should be zeroed
if one knows that the mathematical result is a real number.

Note that due to this problem, the plot function fails with:
  *** plot: impossible assignment t_COMPLEX --> t_REAL.

Vincent Lefèvre <> - Web: <>
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Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)