Try this:
use Math::Cephes qw/acos/;
for ( -2, -1.1, -1, 0, 1, 1.1, 2 ) {
  print acos($_),$/;
}

[download]
I expect you are getting something similar (i.e. #QNAN), as I am guessing some of the values $d are outside the domain of the "Real" solutions of acos.

-enlil

In reply to Re: Re: Maybe I'm just dumb... by Enlil
in thread Debugging a sort in PDL routine by Evanovich

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