There are times when Perl’s inbuilt exponentiation operator, **, just doesn’t cut it:

16:46 >perl -wE "my $cube_root = (-8)**(1/3); say $cube_root;"
NaN

16:46 >perl -v

This is perl 5, version 32, subversion 1 (v5.32.1) built for MSWin32-x
+64-multi-thread

[download]

I note in the documentation that ** “...is implemented using C's pow(3) function...”, and that’s where the limitation appears to lie. (I’m using Strawberry Perl running under Windows 8.1 64-bit. I get the same results using Raku. I don’t know if C’s pow(3) function has the same limitations under Unix?)

I came up with the following, which works for my use-case but is really a kludge:

sub cube_root
{
    my ($n) = @_;

    return (abs( $n ) ** (1 / 3)) * ($n < 0 ? -1 : 1);
}

[download]

So, what’s the quickest/simplest/correct way to get Perl to act like the calculator app that comes with Windows, and give -2 as the cube root of -8? (I’m only interested in the real solution.) I had a quick look through CPAN, but nothing stood out. I’m probably overlooking the obvious.

Thanks,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to How to get better exponentiation? by Athanasius

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.